I just took my latest Chevelle to GoodGuys on a beautiful 75 degree day and for the most part it ran well, but it gets real hot in slow traffic. It's an all stock 327/300 with a 2 inch steel fan shroud, a stock fan and clutch (which is new). The fan is spinning but is not locked up. The coolant is flowing well but we measured the temp at 218 degrees after driving it in town in slow traffic and the gauge is 3/4 of the way up. It cools OK when I am on the freeway, down to about half gauge. The tstat is a high volume 180.

I'd like to be down around 200 to 210 in town but I also would like to keep the stock components since it is all original. Any suggestions?

Thanks
Chuck

A fan clutch a filled with a viscus fluid and is designed to allow the fan to spin freely when cold, this allows the engine temp to heat up faster in the cold weather, the fan clutch should be pretty darn stiff to turn once up to operating temp. Get the car hot and shut it off, if the fan spins easily you need a new fan clutch, it is not allowing the fan to move much air at idle and low speeds, I would try a new one and see what happens. Even new parts can be bad. A partially plugged radiator will cause this also.

A fan clutch a filled with a viscus fluid and is designed to allow the fan to spin freely when cold, this allows the engine temp to heat up faster in the cold weather, the fan clutch should be pretty darn stiff to turn once up to operating temp. Get the car hot and shut it off, if the fan spins easily you need a new fan clutch, it is not allowing the fan to move much air at idle and low speeds, I would try a new one and see what happens. Even new parts can be bad. A partially plugged radiator will cause this also.

Thanks Jason. It IS a new clutch and when it is at 220, like today, I spun the fan and there was some drag, but it spun nearly a half a turn before stopping. It certainly was not locked up or close to it. The drag was mild. Now where did I put that receipt?

Thanks
Chuck

Jasons right. At that temp. You should nearly be able to turn the engine over with the fan...

Chuck,i am assuming here the temp gauge is accurate (which it may not ,be),the t-stat is working properly,radiator is in good cond and of correct capacity/rows for your setup/motor and proper fan is being run which i think is a 5 blade setup for your chevelle along with the proper fan shroud and proper fan blade to fan shroud clearance too.

Also,have you verified the 218 deg temp is correct when sitting still? I use an inexpensive pocket thermometer with a metal probe like they use in automotive ac shops to chekc the coolent temp,its close enough to do the job. I just remove rad cap with motor cold and let it sit running untill in you case it hits the 215-220 range and then stick the metal prpbe of the thermometer into the rad filler neck to get the actual coolent temp.

I always to that as a base reading to know for a fact what the temp is beofre possibly going nuts chasing your tail if in fact the cars temp gauge is giving worng/improper readings as doing that will allways ets things right from the begining as far as what is the temp at.

So after all thats verfied lets get into some suggestions.

With in traffic heating up the issue i would 1st ensure there's enough base timing with non stock non gm cam like 16-18 deg,much less then that starts to increase idle temp,just how much depends on how many deg the base timing is retarded along with the particular setup.

You also need vacuum adv hooked to full intake vacuum and not ported because if i am not mistaken it was you that said in the recent past you were running ported vacuum on vac adv for better sounding/lopy idle due to less timing at idle/low engine speed which will make motor run hotter too esp at idle if thats the case,if allready running vac adv to full int vacuum then ignor this.

Now when your motor is running a verified real 218-220 deg f in traffic/sitting still your fan clutch should be fully locked up and since it's' not that tells me its either defective or its is locked up and you dont realize it. The std duty fan clutches dont lock up that much when heated up which can be mistaken for not being fully locked up when they are in fact locked up. Thats why i always run the HD/AC type clutch fan setups for most all sbc/bbc street perf motors with very good results because they lock up slightly earlier and lock tighter for more rpm when heated up in traffic too which has always for me resuled in a reduction of in traffic temps when installing a hd vs std duty fan clutch.

But if yours is in fact supposed to be a hd/ac fan clutch something is wrong with it because at 218-220 deg f the fan clutch should be fully locked up and you should see & hear plenty of fan noise/rpm and if not somethign is wrong unless the temp gauge isnt reading properly and its not at 220 deg and its only 200-210 and you dont know it.

But dont run an extreem duty fan clutch,that looks up too much which results a lot of fan noise/sig reduced fuel mileage/lost power/and too much dust & dirt being pulled into engine compartment.

But again, i often find even for a mild setup like yours the std duty clutches dont cut it and the ac/hd duty type do a much better job of cooling because they lock at a slighly lower temp and also lock up tighter for more fan rpm when they heat up in traffic then the std duty clutch does.

Make sure the idle mixture isnt set too lean too which can also affect idle and low engine speed temps.

With man trans set idle a ittle higher to lke 900-950 rpm for more fan rpm too.

If running mech temp gauge with metal temp sender cable make sure to isualte it from motor to firewall because when it gets heat soaked that can failsely drive the temps approx 5-8 deg hotter too so your 218 deg would then be 210-213 deg f.

Lastly,if temp sender is in head vs intake that will read approx 6-10 deg f hotter then the rest of the motor is seeing at that same time due to proximity to ex port/ex manifold so keepthat in mind too.

In that case your 218 deg f could be on avg more like approx 208 deg f on low end & 212 deg f on hi end which is a little better then 218 deg f .

Now put that along with what i mentioned above it you have a metal temp sender cable thats geting heat soaked in traffic & in that case your temp would he a little lower yet at approx 198-202 deg f on the low end to 202-208 deg which s even better yet.

Now if all that doesnt get your temps down if you have the 5 blade fan i would try gms newer 772 7 blade clutch fan that may pull in more air at idle if it fits your fan shroud and fan clutch.

But again i am assuming all else i 1st metnioned is ok with you cooling system as you stated esp the radiator . But if the rad was partially clooged you would aslohave crusie tempissue too esp wit motor workng more at cruise andthats not the case so its likely ok.

As long as the radiator,water pump,fan shroud,& fan are ok Higher temps "AT IDLE ONLY " usually many times end up being issues " COLLECTIVELY " with poor airflow thru the radiator,std duty fan clutch not locking up enough for good fan rpm & airflow thru rad(try a hd/ac type can clutch),retarded base timing with perf cam(adv to 16-18 deg base & 36-38 total),lean idle mixture(chk idle mix),no vac adv @ idle(hook to full int vacuum),etc.

But there is no reason why your mild sbc should run too hot in traffic with a stock cooling system in good operation cond as long as everythng is right,1 ,2,3 things not right like base timing and no vac adv at idle or std duty clutch vs hd-ac type clutch and it will run hotter in traffic @ idle every time.

Let us know how you make out if you bother to chk these things out.

Scott

Chuck,i am assuming here the temp gauge is accurate (which it may not ,be),the t-stat is working properly,radiator is in good cond and of correct capacity/rows for your setup/motor and proper fan is being run which i think is a 5 blade setup for your chevelle along with the proper fan shroud and proper fan blade to fan shroud clearance too.

Also,have you verified the 218 deg temp is correct when sitting still? I use an inexpensive pocket thermometer with a metal probe like they use in automotive ac shops to chekc the coolent temp,its close enough to do the job. I just remove rad cap with motor cold and let it sit running untill in you case it hits the 215-220 range and then stick the metal prpbe of the thermometer into the rad filler neck to get the actual coolent temp.

I always to that as a base reading to know for a fact what the temp is beofre possibly going nuts chasing your tail if in fact the cars temp gauge is giving worng/improper readings as doing that will allways ets things right from the begining as far as what is the temp at.

So after all thats verfied lets get into some suggestions.

With in traffic heating up the issue i would 1st ensure there's enough base timing with non stock non gm cam like 16-18 deg,much less then that starts to increase idle temp,just how much depends on how many deg the base timing is retarded along with the particular setup.

You also need vacuum adv hooked to full intake vacuum and not ported because if i am not mistaken it was you that said in the recent past you were running ported vacuum on vac adv for better sounding/lopy idle due to less timing at idle/low engine speed which will make motor run hotter too esp at idle if thats the case,if allready running vac adv to full int vacuum then ignor this.

Now when your motor is running a verified real 218-220 deg f in traffic/sitting still your fan clutch should be fully locked up and since it's' not that tells me its either defective or its is locked up and you dont realize it. The std duty fan clutches dont lock up that much when heated up which can be mistaken for not being fully locked up when they are in fact locked up. Thats why i always run the HD/AC type clutch fan setups for most all sbc/bbc street perf motors with very good results because they lock up slightly earlier and lock tighter for more rpm when heated up in traffic too which has always for me resuled in a reduction of in traffic temps when installing a hd vs std duty fan clutch.

But if yours is in fact supposed to be a hd/ac fan clutch something is wrong with it because at 218-220 deg f the fan clutch should be fully locked up and you should see & hear plenty of fan noise/rpm and if not somethign is wrong unless the temp gauge isnt reading properly and its not at 220 deg and its only 200-210 and you dont know it.

But dont run an extreem duty fan clutch,that looks up too much which results a lot of fan noise/sig reduced fuel mileage/lost power/and too much dust & dirt being pulled into engine compartment.

But again, i often find even for a mild setup like yours the std duty clutches dont cut it and the ac/hd duty type do a much better job of cooling because they lock at a slighly lower temp and also lock up tighter for more fan rpm when they heat up in traffic then the std duty clutch does.

Make sure the idle mixture isnt set too lean too which can also affect idle and low engine speed temps.

With man trans set idle a ittle higher to lke 900-950 rpm for more fan rpm too.

If running mech temp gauge with metal temp sender cable make sure to isualte it from motor to firewall because when it gets heat soaked that can failsely drive the temps approx 5-8 deg hotter too so your 218 deg would then be 210-213 deg f.

Lastly,if temp sender is in head vs intake that will read approx 6-10 deg f hotter then the rest of the motor is seeing at that same time due to proximity to ex port/ex manifold so keepthat in mind too.

In that case your 218 deg f could be on avg more like approx 208 deg f on low end & 212 deg f on hi end which is a little better then 218 deg f .

Now put that along with what i mentioned above it you have a metal temp sender cable thats geting heat soaked in traffic & in that case your temp would he a little lower yet at approx 198-202 deg f on the low end to 202-208 deg which s even better yet.

Now if all that doesnt get your temps down if you have the 5 blade fan i would try gms newer 772 7 blade clutch fan that may pull in more air at idle if it fits your fan shroud and fan clutch.

But again i am assuming all else i 1st metnioned is ok with you cooling system as you stated esp the radiator . But if the rad was partially clooged you would aslohave crusie tempissue too esp wit motor workng more at cruise andthats not the case so its likely ok.

As long as the radiator,water pump,fan shroud,& fan are ok Higher temps "AT IDLE ONLY " usually many times end up being issues " COLLECTIVELY " with poor airflow thru the radiator,std duty fan clutch not locking up enough for good fan rpm & airflow thru rad(try a hd/ac type can clutch),retarded base timing with perf cam(adv to 16-18 deg base & 36-38 total),lean idle mixture(chk idle mix),no vac adv @ idle(hook to full int vacuum),etc.

But there is no reason why your mild sbc should run too hot in traffic with a stock cooling system in good operation cond as long as everythng is right,1 ,2,3 things not right like base timing and no vac adv at idle or std duty clutch vs hd-ac type clutch and it will run hotter in traffic @ idle every time.

Let us know how you make out if you bother to chk these things out.

Scott

I... 2nd the motion

Scott,
I agree and, as you can imagine, I did all the things you listed and I am running 18 degrees advance and 38, all in. The clutch is a Hayden and they say they do not offer a heavy duty fan for a 65 with a 327. Maybe it's a small block issue. I will ask if they have one for a Z-16 or a 70 SS396. I'd bet they do have a heavy duty for a big block and that it is the exact same foot print. I don't believe the new (std duty) will be any better than the last one. Let me try that first.

........... I just got off the phone with Hayden and they do NOT offer a heavy duty clutch except for different cars with different dimensions. Does anyone have a part number and manufacturer for a heavy lock up fan clutch? I can't believe how much time I have wasted on a stupid fan clutch LOL.

Thanks
Chuck

Make sure your fan is the correct distance into the shroud. If it is too far in or out it will not draw the air correctly.

Make sure your fan is the correct distance into the shroud. If it is too far in or out it will not draw the air correctly.

Thanks Ed. I only have about a 1/4 inch before the clutch hits the radiator and I am using the stock shroud so...it is, what it is.

Does anyone have a part number and manufacturer for a heavy lock up fan clutch?

(UPDATE) Scott, I called Napa and they only have one...from Hayden, and it's the standard duty Hayden 2710 that I have now. Any other ideas?

Thanks
Chuck

Chuck,try to look up in gm info if 327 & 396(65 only) impalas, vettes and or turcks used same pt# clutch fan to see if those have a hd/ac type can clutch listed for tem under a different pt#.

If you find some other cars/trucks used the same pt# clutch fan which i bet thee did then look for a hd and or ac fan clutch application for the truck and or vette etc 327 or bbc that used same fan in approx same yr with the short water pumps they used back then and you will then find a hd/ac fan clutch.

I am sure someone still mfgs a hd/ac fan clutch for your setup,you just have to get sly by doing the cross ref matching thing to find one,i have done this very thing many times tofind things when not listed and it works.

I used to work in auto parts industry yrs back and i can tell you that there are issues these days with corrunpted/incorrect data/listings in just about anything i look up these days for our 35-40yr + old cars/motors,i see things wrong and or completely missing all the time.

MAYBE IF YOU COULD FIND YOUR FANS PT3 YOUCOULD THEN POST THAT IN ANOTHER FORUM HERE IN T/CEVELLE LIKE THE ORIGINALITY OR BY THE 3'S TOASK SOME IF THEY CAN LOOK YOUR FAN ID UP TO SEE WHAT OTHER CARS/TRUCKS IT CAM ON SOYOU CAN THEN TRY TO SEE IF YOU CAN FIND DH/AC FAN CLUTCH LISTINGS FOR THOSE APPLICATIONS.

Scott

Do you happen to have a non-clutch fan set up you could install temporarily to confirm it is the clutch that is the problem?

Isn't the 327 a fresh rebuild? My L79 ran hot for a few years (not much driving) and until it got fully broken in it always ran on the hot side. On really hot days, I'll just run the heater through the defroster on high if I get stuck at a stop light. You'd be amazed how much that can bring the temp gauge down.

I found my '65 gauge to be pretty reliable. With the needle pegged right in the middle seems to be the correct temp. Mine doesn't fluctuate much anymore unless it is really hot (above 90) and I get stuck in stop and go traffic. Even a small amount of motion seems to keep the temp gauge just to the HOT side of the center of the gauge. Running high octane fuel helps some too and lean carb settings can make things too hot.

Chuck, Just put a Flex a lite fiberglass fan, no clutch, and see if that is the problem. If you can't get a decent clutch then it solves the problem too, but not as stock...

Ron

Do you happen to have a non-clutch fan set up you could install temporarily to confirm it is the clutch that is the problem?

Isn't the 327 a fresh rebuild? My L79 ran hot for a few years (not much driving) and until it got fully broken in it always ran on the hot side. On really hot days, I'll just run the heater through the defroster on high if I get stuck at a stop light. You'd be amazed how much that can bring the temp gauge down.

I found my '65 gauge to be pretty reliable. With the needle pegged right in the middle seems to be the correct temp. Mine doesn't fluctuate much anymore unless it is really hot (above 90) and I get stuck in stop and go traffic. Even a small amount of motion seems to keep the temp gauge just to the HOT side of the center of the gauge. Running high octane fuel helps some too and lean carb settings can make things too hot.

Hi Rich,
I don't have a non clutch set up to test with and the motor is original with 58K miles on it so break in is not an issue. My gauge runs right in the middle when I have air flow (moving). The L79 has the wide shroud and mine has the 2 inch shroud so that may be part of the problem. I added water wetter and installed the new clutch, although it's a standard clutch. I measured the temp and it was stable at 220 (max, not climbing) when hot in stop and go, so I agree that the sender is correct. I did drain out 12 oz of coolant mix from the bottom of the rad to add the same amount of wetter plus I added an additional TWO 12 oz bottles of water to bring it back up to full so I may have had some air trapped. The tstat (180) is opening and flowing well. I am driving it to the West Coast Chevelle Get Together in Sac this weekend and we'll see what happens.

Thanks, I hope all is well. Thanks Scott.
Chuck

I haven't carefully read all the previous posts- here goes- A/C car with a/c condenser in front of the radiator? large 4 core radiator?

Chuck,i still think its a simple airflow issue and the std fan clutches sold these days dont lock up much and could really be you problem at this point .

I tried to cross reff your setup to vettes/trucks /impallas etc of same approx yrs and man i could find 1 that had a hd/ac type fan clutch anywhere and in tha past i can usually come up with something.

But another option i ran into while looking arround on the hayden site is that they sell a few different size clutch fans for better cooling that i think are 6 blade in a coupled ifferent sizes that do accept their hd/ac type fan clutch.

So with that said go some where that sells hayden items and have them look up your application and then some fans with also show up as options as replacement fans for your car/ motor. The description for the fans say they accept mult type fan clutches having universal /mult holes to accept mult fan clutches. Maybe you could then find a hd/ac type fan clutch that fits that universal type replacement fan that will work for your setup.

This may be you best option for getting a hd/ac type THERMOSTATIC fan clutch and fan setup for you car short of hitting the junk yards and going thru them untill you maybe find what combo from late 70's early 80's that will work for you.

BTW,i see you mentioned your fan shroud is in question so make sure you have the proper fan shroud that would have been used for an ac application for your car. Thats because if the fan shroud setup isnt right that can also limit/greatly reduce the fans efficiency/ability to pull enough air thru the radiator while idling in traffic for proper cooling.

Scott

Chuck,chk your email.

Scott

Chuck,chk your email.

Scott

Got it. Thanks buddy!
CB

If yours is all stock your 327 and my L79 should have the same radiator, shroud, etc. The L79 did get a different radiator, but the only real difference is where the upper hose attaches, the radiators are within one pint of being the same size. The spacer between the radiator and the radiator support should be the same and the shroud should be the same. The fan blades should be half in and half out of the shroud. Not sure why this makes so much difference with the rinky-dink seemingly useless shroud that is used, but it does seem to make a difference.

If yours is all stock your 327 and my L79 should have the same radiator, shroud, etc. The L79 did get a different radiator, but the only real difference is where the upper hose attaches, the radiators are within one pint of being the same size. The spacer between the radiator and the radiator support should be the same and the shroud should be the same. The fan blades should be half in and half out of the shroud. Not sure why this makes so much difference with the rinky-dink seemingly useless shroud that is used, but it does seem to make a difference.

I am good with that but mine has the 2 inch (front to back) shroud:
http://www.opgi.com/product.asp?topcatid=11&chapterid=11&topvalue=0&newflag=0&grpcode=13246&yearrange=1965

Isn't the L79 shroud about 4 inches deep?

CB

[QUOTE=SWHEATON;2283968]


Also,have you verified the 218 deg temp is correct when sitting still? I use an inexpensive pocket thermometer with a metal probe like they use in automotive ac shops to chekc the coolent temp,its close enough to do the job. I just remove rad cap with motor cold and let it sit running untill in you case it hits the 215-220 range and then stick the metal prpbe of the thermometer into the rad filler neck to get the actual coolent temp.( Quote


Wow! I am wondering how you do that. Water and properly mixed antifreeze boils at 212* F. Thats like what happens with the radiator cap off. How'd you stop it from boiling at 215-220*F. The only way to stop the coolant from boiling at greater than 212*F is to pressurize the system.

Try this : Put your temp gauge in a pot of water on the stove ( the temp gauge cannot touch the pot for this test)and turn the burner on hi. Then stand there and see if the temp gauge goes over 212*F for the entire time it takes for ALL of the water to boil away. I am betting it won't.

You must be very fast! If I were checking the temp of a system that was open to the atmosphere at that temperature range I'd be moving very fast too!

I am good with that but mine has the 2 inch (front to back) shroud:
http://www.opgi.com/product.asp?topcatid=11&chapterid=11&topvalue=0&newflag=0&grpcode=13246&yearrange=1965

Isn't the L79 shroud about 4 inches deep?

CB

Nope. There really is no such thing as an "L79 shroud". The L79 used the same shroud as used on any other Chevelle that got AC or the heavy duty cooling package (which consisted of a clutch fan, slightly larger radiator and a shroud). The shroud you provided a link to is the same one I have.

FWIW, the stock temp gauge in my 69 goes nearly to the peg when the car is fully warmed up, but my mechanical Autometer temp gauge reads 185. I would make SURE the car is really running hot before throwing any money at it. JMHO.

Something just occurred to me this afternoon. Did you happen to paint the radiator? Radiator paint used by radiator shops is special and if you paint a radiator with regular paint it can cause a car to overheat, ask me how I know.

Esp if you lay the std non radiator paint on too thick.

Eastwood sells paint esp designed for radiators but even that i use sparingly on the radiator core & fins to ensure its doesnt go on too thick affect cooling.

Scott

Nope. There really is no such thing as an "L79 shroud". The L79 used the same shroud as used on any other Chevelle that got AC or the heavy duty cooling package (which consisted of a clutch fan, slightly larger radiator and a shroud). The shroud you provided a link to is the same one I have.

It looks like I have the same one. I should be about 2 inches thick on the barrel.

Esp if you lay the std non radiator paint on too thick.

Eastwood sells paint esp designed for radiators but even that i use sparingly on the radiator core & fins to ensure its doesnt go on too thick affect cooling.

Scott

Thanks Scott. I will check it this weekend. Remember that I AM running ported vacuum as I reported before. I like the idle that way. I may have to change it back to full vacuum but I am trying to improve the cooling by other methods if I can. This certainly is the root problem but I thought that it might help if I could get a HD clutch that would lock up instead of the Hayden "milk toast" clutch I have now.

Thanks
Chuck


CB

Bill,yup it will be a boiling for sure if in fact its really running that hot & the temp gauge is reading correctly.

At that point he would not even have to chk the temp because if it starts to boil with cap off with no pressure on the system then he knows the coolent is already at or over 212 deg F as you stated it would do. I just didnt bother to state that because i thought it would be obvious to the person doing the checking if the coolent was starting to boil it was in fact at or over 212deg F at that point.

Scott

Chuck,,you have to get away from the ported vacuum as i suggested to you mult times,that is part of the problem!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

AM I GOING TO HAVE COME ALL THE WAY FROM THE EAST COAST( NY) TO THE WEST COAST (CA) WHERE YOU ARE TO MOVE THAT DARN VAC ADV FROM PORTED TO FULLINT VACUUM WHERE IT BELONGS IN YOUR CASE? (LOL!!!)

Dont forget in the late 60's-eraly 70's the car mfg's went to ported vacuum on vac adv to considerably retard the idle timing making the motor run hotter @ idle which increased exhaust temps to help lower emissions. The ported vacuum makes the motor run considerably hotter due to no vacuun adv at idle retarding the timing by 10-15-and in some cases 18-20deg which is a lot so change to full int vacuum for vac adv as i already suggested to you at least 3 times now and why it was importatnt to do so in your case with the motor running hot only at idle.

I have seen times where people changed from ported to full int vacuum all the time the idle/traffic temps dropped 8-10 deg f and in some cases 10-15+ deg f just from doing that.

So since its no big deal to swap the vac adv from ported to full int vacuum in 1 minute so why the heck dont you try that out for a few test rides to see it it does?

Between you running "incorrect ported vacuum " (esp with the L79 cam with considerably more duration that need more timing at idle) and also " have a lazy std duty fan clutch " thats not locking up much when motor /radiator gets hot resulting in not enough fan speed at idle to pull enough air thru the raidator at idle i bet the bank those 2 items are what's causing your higher idle/in traffic temps. Also make sure to run approx 950rpm (not 750-800rpm) idle with man trans to help fan pull more air in.

Sorry about beating this to death but since your still refusing to get away from running ported vacuum after being reminded mult times its part of the problem i felt i had to get the point to you that your setup very likely cant handle that. The significantly retarded timing(10-20deg) at idle with ported/no vac for vac adv @ idle can cause sig higher motor temps.

So you have to give up that retarded timing lopey idle the ported vacuum creats in order to get the idle/low speed temp down some along with a better hd/ac fan clutch setup of some kind that will lock up better for more fan rpm at idle and or a fixed fan that will pull more air in.

If you cant find a fan clutch setupthat works better then go to the flex-a-lite site and they offer fan spacers and fixed fans that will work for your setup if you need to go that route.

Also make sure your idle mixture isnt too lean too .

Good luck.

Scott

I think I found the problem... and it wasn't ported vacuum which I said I changed in a previous post.

I got frustrated so I went back to the beginning and rechecked everything from square one. What I found was a timing issue. I re-checked the timing and with the vacuum line plugged (mechanical only) it tops out at 35 degrees all in. That relates to 20 degrees at idle. Before I was at 16 at idle and God knows what all in. I thought we were at 19 at idle. I am using a stock distributor, the one that came with the car, and I think the springs are way to heavy. The mechanical advance comes on way to slow and total advance is too low causing the idle timing to be too low as well. I will change some springs but for now I have 35 all in and 20 at idle and when I reconnect the (manifold) vacuum I get a ton of throttle response and a much cooler car. Hopefully it won't ping. I'd like to see more timing all in and less at idle (36 & 18). I left it in gear at idle for 15 minutes and it never went over half gauge.

Chuck

I have a 468 in my driver, P.S.-A/C-.... I had a heating problem with it on 90 degree days with the A/C running. It is 100% stock-- 4 core --772 fan--811TX water pump. I got a CHEVY fan clutch designed for a mid to late 80s -454 - 3/4-T--Suburban with dual A/Cs. It fits inside the 772 fan and I am as happy as a fat rat.
It has drag on it, And the wagon has been parked for months. It aint cheeeeep, But no more cooling problems, YES it is loud when it is hot.
The wagon will go to 215 on a 90 degree day in traffic with the A/C on. Thats my story and I am sticken to it !!!
Bob

I have a 468 in my driver, P.S.-A/C-.... I had a heating problem with it on 90 degree days with the A/C running. It is 100% stock-- 4 core --772 fan--811TX water pump. I got a CHEVY fan clutch designed for a mid to late 80s -454 - 3/4-T--Suburban with dual A/Cs. It fits inside the 772 fan and I am as happy as a fat rat.
It has drag on it, And the wagon has been parked for months. It aint cheeeeep, But no more cooling problems, YES it is loud when it is hot.
The wagon will go to 215 on a 90 degree day in traffic with the A/C on. Thats my story and I am sticken to it !!!
Bob

Thanks Bob. Is it the same dimension front to back? Great tip!

Chuck

You could also put a bottle of redline water wetter in the radiator. It will not fix your mechanical issues, but it does drop the temp. If you use just water and redline it drops the the temp around 20. I use it instead of antifreeze, works as stated and have had no problems. Use antifreeze if you live where temps drop below freezing, redline doesn't protect below 32 alone.

Hi Chuck,
Maybe you have your info, but when my Chevelle was overheating at Hot August Nites, I 100% solved it with an Alumitech rad, fan clutch & shroud. Since I didn't originally have any of these on the 283, I had to figure out what clutch to get. Go to the Hayden site, www.haydenauto.com/catalogs/index.htm. Click on Fan Catalogs and Fan Blades. Scroll down to pg 4 and it has all the dimensions for various clutches. At pg 20 you can see whats applicable to your specific car. Then you can find a HD clutch and figure out if it'll fit your car. Takes a little while figuring the spacing, but it's worth it. Unless the car is 100% original, you can sub a different clutch and nobody will know.

Jim M

Chuck

Hayden has a website. You can go to it and probably find a part number that will work. It's what I did for my 468 olds. I haven't put it on yet.

Larry

Hi Chuck,
Maybe you have your info, but when my Chevelle was overheating at Hot August Nites, I 100% solved it with an Alumitech rad, fan clutch & shroud. Since I didn't originally have any of these on the 283, I had to figure out what clutch to get. Go to the Hayden site, www.haydenauto.com/catalogs/index.htm. Click on Fan Catalogs and Fan Blades. Scroll down to pg 4 and it has all the dimensions for various clutches. At pg 20 you can see whats applicable to your specific car. Then you can find a HD clutch and figure out if it'll fit your car. Takes a little while figuring the spacing, but it's worth it. Unless the car is 100% original, you can sub a different clutch and nobody will know.

Jim M

Good idea, Jim. In fact I just got the Hayden catalog in the mail yesterday. Here's a new twist though. I just got back from a 45 minute drive to San Jose to attend the Chevelle Club meeting. I added some timing yesterday and it is running cooler with the addition of a bottle of Water Wetter, but it's still almost 3/4 scale on the freeway at 60 MPH with an outside temp of about 68 degrees. Coolant temp is about 215.

When I got home I wanted to check the radiator area right in front of the clutch to see if a blockage could cause that area to be too cool to heat the clutch thermostat engage the clutch. In other words, the problem may be that the radiator in the center may be too cool to cause the fan to lock up.

What I found was that I could put my hand almost anywhere on the front fins of the radiator and hold it there without burning myself. The thermometer confirms that it is only 90 degrees on the fins at the front of the radiator. It warms up when the motor is turned off, but not much. The top filler area of the radiator is real hot and can not be touched. Even if you consider the cooling effect of the fins I would have thought the front of the radiator fins would be much hotter than that with a coolant temp of almost 220 degrees.

Maybe I do have a blocked radiator. Certainly the clutch is not getting hot enough in the current configuration to engage. My car uses a Hayden 2710 and a 2747 HD unit is available with a 3.25 inch fan bolt circle. Maybe I can find a 3.25 fan to go with the HD unit??? Any thoughts????

Chuck,you said adv the timing helped lower temps a little but it satill seems to be running hot by the temp gauge,have you verified its turely running that hot and that the gauge is correct?

Whats the age of the radiator and is it a 2 or 3core?

If gauge s correct and motor is truely running that hot then from what you describe about the radiator says to me its partially blocked and or is old enough where the fins are not properly tranfering heat from the radiator tubes so te fins feel cooler then they should be of the tubes are cloged.

Thats why when you 1st stated you were now having heating up issues when at cruise speeds that i suggested the radiator was very likely having problems and to get it checked out.

I would remove the rad to have the fins checked at a rad shop to ensure they are not rotted/corroded enough at the fin to radiator tube interface/bond to not properly trasnfer heat from rad tubes to fins anymore which will cause overheating.

If the fins check out ok then have the radiator boiled out and properly pressure tested to ensure all tubes are clear after boiling it out & there are no leakes post that work.

If all tubes arent clear post boiling replace the radiator.

But if this radiator is already 8-10yrs old and it seems to have clogged tubes i would opt to not chance investing more money into it for cleaning/boling/pressure testing/etc (due to its age) just to maybe find out it doesnt clean up well and doesnt cool properly.

Then you have just wasted $100 which is approx 35%-40% cost for a new stock rep radiator.

I would opt for a new radiator at that point IMHO.

But i am assuming all is correct /ok with the t-stat,water pump is operating-pumping properly,or that you dont have any issues like a rad hose collapsing when at cruise speed blocking proper coollent flow.

Good luck.

Scott

I installed a Hayden HD 2747 in my Chevelle, but that's the HD model that had the mounting dimensions I needed, to put the fan just into the shroud. Strange deal about the temp of your radiator. I take it this was right after returning with the temp needle 3/4 scale. Sounds like a rad problem, or the water pump's not pushing the water thru.

Thanks Scott. The car is all original and was very well maintained so it may just be age and corrosion that did it in. I verified with a thermometer (in an earlier post) that it is running 215+.

What's really strange is that I am running 20 degrees advance at idle, before connecting vacuum advance, and it does not ping and runs well after connecting the vacuum advance. Someone suggested that the dampner may have rotated at the polymer giving me an incorrect reading because 20 degrees initial should ping under load. It runs cooler when I add advance. Maybe I should verify TDC on the dampner. It's strange to have it run so well at 20 degrees initial.

I still think there is a flow problem. I think you are right. The radiator is clean and free of any dents or problems to the fins visually. I suspect that it is blocked. This was in a barn for 20 years and may have never been rotted out since day one, for all I know. Pay checks are scarce around my house right now so I will gamble on the radiator shop. He has done a couple for me and even gave one back to me with no charge when flow was found to be good. Next step after that will be a heavy duty fan clutch if I can find one but, as noted in a previous post, I can't expect much from the existing fan clutch if it is seeing only 100 degrees.

Thanks
Chuck

I installed a Hayden HD 2747 in my Chevelle, but that's the HD model that had the mounting dimensions I needed, to put the fan just into the shroud. Strange deal about the temp of your radiator. I take it this was right after returning with the temp needle 3/4 scale. Sounds like a rad problem, or the water pump's not pushing the water thru.

Exactly. A 2747 looks like the HD replacement for the Chevelle except that it has a 3.25 inch bolt pattern instead of a 3.00 pattern. What fan did you use? I need a 17 inch fan.

Thanks
Chuck

Thanks Jason. It IS a new clutch and when it is at 220, like today, I spun the fan and there was some drag, but it spun nearly a half a turn before stopping. It certainly was not locked up or close to it. The drag was mild. Now where did I put that receipt?

Thanks
Chuck

If the Chevelle would stay at 220 in traffic I would be happy. We went to the good guys car show in Del Mar. We were in traffic for about 25 minutes or so. By the time we got parked the temp in the Chevelle was up to just about 250.

I don't know why it overheats like that, but from what I've been told it's done it since it was new.

The fan I used was out of a late 60's Buick GS, I think, p/n 1239013. Got it at a wrecking yard. It's a 7 blade.

Chuck,its not really that uncommon for a motor with even a mild perf running well with 20 deg base/inital timing & not ping.

My 396 has a mild perf cam with 14.5-15" idle vacuum & 222deg @.05 deg dur on 112 DEG LSA and it runs best with approx 19-20 deg base timing.

The cam your running may have enough duration to relieve some of the cyl pressure so it doesnt ping.

Scott

Chuck,its not really that uncommon for a motor with even a mild perf running well with 20 deg base/inital timing & not ping.

My 396 has a mild perf cam with 14.5-15" idle vacuum & 222deg @.05 deg dur on 112 DEG LSA and it runs best with approx 19-20 deg base timing.

The cam your running may have enough duration to relieve some of the cyl pressure so it doesn't ping.

Scott

That makes a lot of sense, Scott. I have decide to take the Rad in for a check up and boil out. We checked it today with a heat gun and there was 25 degrees difference between the hot front edges, and the center of the rad. I think, as you suggested, it's all plugged up from years of sitting.

Thanks
CB

Hi Chuck,let us know how things go after having the radiator boiled out and cleaned.

Scott

Just to throw my $.02 in here, I have had two vehicles that, over time, seemed to run hotter and hotter, with no other changes. I replaced the radiator in both, and that fixed it. One was an 82 Bronco, in 2004 or so. Not cheap, but it ran as cool as when I bought it 5 years prior. It was my toy hauler, so cooling while towing was important. It also survived a conversion to 134 ac.

Ron good point but i guess you missed the point that Chuck has stated he's on a very strickt /tight budget and cant just pop for a new radiator.

And that was even after i reminded him that it may cost $80-100 to get the current radiator boiled/cleaned etc which could be 35-40% the cost of a new radiator right there that could be wasted if the old rad wouldnt clean out well enough for any improment. I suggetsted he put that money towards a new radiator and be done with it but he is going to try the other route due to money constraints which doesn't grow on trees for most of us including me. (LOL!!!!)

Scott

OK, here's the latest. I had the radiator rodded out and they said it was 15% to 20% blocked, not a huge deal but worth doing. I also found a heavy duty clutch, not intended for Chevelles but it is the one that would have been for a Chevelle if they offered a heavy duty fan clutch. It the same as the stock 2710 except the HD clutch has a 3.25 inch bolt pattern rather that the 3.0 inch bolt pattern on the stock fan clutch. The HD clutch for chevelles is a Hayden 2747, as recommended by Malibu Jimbu (THANKS!). The fan needed to be replaced to accommodate the 3.25 inch bolt pattern on the HD clutch and so I used a Fex-A-Lite 5718, 18 inch fan. It has both the 3.0 and 3.25 inch bolt patterns drilled in it and I now have 6 blades rather than the stock 5. The HD clutch spins much faster and you can feel the air being sucked through the rad, even at idle and low temp. This is the combo to use.

It is a 75 degree day here in California today so I took it for a spin in local traffic. The temp gauge ran up to 3/4 scale and stopped there. I measured the coolant temp and it is 200 degrees so I am going to replace the temp sensor (it was new). 200 should not be a problem but I don't think I should be at 3/4 scale. At 200 degrees coolant temp, the sensor measured 80 Ohms to ground. I will measure it cold too. Most of my cars ran "at temp" with the gauge at 1/2 scale so that is what I am basing this on. Does this sound like a valid assumption?

Thanks
Chuck

Yes, sounds like the temp sending unit is calibrated wrong.

Yes, sounds like the temp sending unit is calibrated wrong.

Rich, I am not convinced that the coolant in the radiator, where I measured it, is the same as the coolant in the block where the sensor is. I got another new temp sender, removed the other one from the manifold and put both in the freezer for a couple minutes and left them on the bench so they would both come to ambient temp together. They both had the same resistance at room temp. I put them in a pan of water and brought them up to 200 degrees, removed and measured them. Both are within 1 degree of each other at hot, 85 Ohms. The temp sender seems to be correct and it is the one called out for the car/motor.

I am leaning toward a bad thermostat. The temp in the radiator is 200 degrees, but it may be higher in the block if there is insufficient flow. I measured the sender resistance while it was mounted in the intake manifold and when the radiator coolant was at 200 degrees and the sensor in the block coolant read 55 Ohms. I later removed the sensor and when read after being removed from a 200 degree pan of water it read 85 Ohms. That confirms that the water temp in the block is hotter than the water temp in the radiator, because the block coolant must be hotter than 200 degrees for the resistance to go down to 55 Ohms, right? That leads to the conclusion that there is insufficient flow through the thermostat preventing the block coolant from getting to the cooler radiator and equalizing the coolant temp ????

What do you think?
CB

I'd recommend a 180 deg, hi flow thermostat. Can't remember the brand I installed....maybe Stewart or Milodin. If that doesn't work, I'd look at the water pump. I went with an Weiand aluminum, but suspect you want to retain the stock look.

I have a high flow a 180 in there now. It opens but doesn't seem to have much flow. The coolant in the rad barely ripples when it's above 180. It's a new Tstat but I am running out of things to replace.

Chuck

I'd recommend a 180 deg, hi flow thermostat. Can't remember the brand I installed....maybe Stewart or Milodin. If that doesn't work, I'd look at the water pump. I went with an Weiand aluminum, but suspect you want to retain the stock look.


I have a high flow a 180 in there now. It opens but doesn't seem to have much flow. The coolant in the rad barely ripples when it's above 180. It's a new Tstat but I am running out of things to replace.

Chuck

I think I will do an "A"/"B" test today. I will log the resistance of the manifold sensor verses rad coolant temp as measured by a thermometer as the car warms up. At 180-200 the two readings should track each other and stabilize as the coolant flows. If the sensor resistance continues to drop (block coolant getting hotter) and the rad temp stays the same I have to assume that the thermostat is not opening enough to provide sufficient flow.

There really is no low cost way to check the coolant temp in the block.

Chuck

Not to steal Chuck's wonderful cooling thread's thunder, but since it seems like a good place for opinions... I'm having the opposite problem, cools good at street speed, over heats on HWYs, runs around 220-225 :( on a 90º day with A/C on
Brand new 307. Just finished break in
Dual flex-a-lite electric fans
Initial timing set at 8-10º BTDC
I do believe it is the stock ?2? core radiator with condensor in front. I know putting in something like a 3 core aluminum rad. would help, but enough to bring it way down to 195-200º?? Please help...

James, my first thought is that you need more timing. Unless you are running a totally stock cam, I have never run less that 12 degrees initial with the vacuum advance plugged. Then when you plug the vacuum advance in you should have plenty of advance and that alone should make it run cooler.

Chuck

Actually I am running a pretty much stock cam. The engine I have is mostly OEM specs.

James, are your fans blowing in the right direction? I've seen folks install puller fans in front of the radiator and it works fine at slow speeds but as speed increases the air coming in from movement of the vehicle counterbalances the air the fans are moving and thus no or very little air is passing through the radiator.

Chuck, does running the heater on high bring the temps down at all? If so, that would help confirm you have a flow restriction or an inadequate radiator. Could be the water pump as well as the thermostat or even a blockage somewhere in the block/heads.

Rich, my electric fans are on the inside of the engine compartment , pulling air thru the condensor and radiator. What is it about new cars today that lets them run to vegas and back in +95º heat at 80+ mph with A/C on max and not overheat? I figure electric fans would help a lot. Just better designed cooling systems? Aluminum blocks?

Well, for one thing, modern cars are designed to run at higher temps than we would typically tolerate on our vintage rides. Consistent temperatures are also much more condusive to fuel efficiency so most modern cars control temperature exceptionally well often times via the main CPU not just by mechanical or electromechanical means.

Ah thats right, forgot about that whole precision computer timing. Nuts :P

So would adding a big ol aluminum radiator help bring it down that much? I know it will help a little if nothing else

Chuck,if you try a new stat and get same results without not much coollent flow then whats type water pump are you runninbg?

If its a stock rep w-pump that has the low perf cookie cutter type impeller they can cavitate at times when back plate of water pump isnt set properly/close enough to the cookie cutter impeller to reduce cavitaion which reduces pumping pressure leading to reduced coolent flow thru the radiator.

The stock pumps back in the day had good pumping/better flowing cast iron impellers that were completely closed to greatly reduce and or completely stop cavitation all together.

but today even the older stock original casting get a stmaped steel impeller when rblt and or new stock rep punmps get the same stamped steel impeller too.

Thats why when my original #'s matching w-pump let go a few yrs back i installed a Milodon hi flow cast iron hi flow pump that comes with a hi flow impeller design for better coolent flow .

I had the original pump that still had the cast iron impeller in it rblt/restored retainong the cast iron impeller . Nom someday when i feel like it i can reinstall it but at least i still have the original pump all ready to go.

Scott