took about a 25 mile drive in my chevelle with 427, alum heads (around 500HP). i have a 190 thermostat and a new alumitech radiator. everything is new here, everything. the engine has only 30 miles on it plus cam break in, so the rings haven't set yet. anyway, on my drive it was running about 205 according to my high dollar autometer guage. the timing is set right at 35-36 degrees total advance. the car has a 750 proform carb right out of the box and it's running very clean, maybe too clean? i mean the plugs are still white basically. i only mention this because i'm wondering if running lean might be causing some extra heat? anyway, it was about upper 80's when i was driving. it never hit 210 or seemed to want to go up much over low 200's. opinions? do other people experience their cars running warmer on the guage than the thermostat opening temperature? i have another car that runs about 10-15 degrees hotter than the therostat setting all the time, even on mild temp days.

GS,
are you running a fan?, and most of, are you running a fan shroud?
and why a 190 thermostate?
I'm running a new alumitech rad also, fan,and shroud, with a 180 thermostate, in my 66 chevelle ss, has the L78<375hp> I'm running 180, idling,and cruizing on highway.even in traffic.This past week it's been hot/muggy, and it's stays at 180,
So try a shroud if your not.makes a difference.
good luck:thumbsup:

from what you've written ... I'd say two things are going on ... first the motor is not broken in which will cause it to run warm... second you anwsered you're own question... white plugs mean its lean .. & YES it will cause it to run HOT... I belive you're driving around being nice to it so it'll break in so I'd just rejet the pri side of the carb to start with.. then recheck with new plugs & adjust jetting as needed

What's wrong with running 205°? I'll bet 90% of the cars today are running that hot or hotter.

If it runs 205 with a 190 thermostat, that means the cooling system cannot keep up with the heat load being presented to it.

If it runs 205°, it means that the heat being removed at that temperature is equal to the heat being generated. Thermostats are not calibrated exactly, neither are temperature gauges. The 190° thermostat could be opening 5° too high and the temperature gauge could be off by the same amount.

thanks for the input. first off, yes i'm running a shroud with a 7 blade clutch fan. nova, i have no big issues with 205, it's not a bad temp and i do have 8 quarts of oil so it would run forever at that temp i suppose. but i think it should run 190 or close to it. i agree, a thermostat could be off a few degrees, but unlikely it'll be off 15. i spent $500 on a radiator because i didn't want any cooling issues to interfere with driving enjoyment. so i'm just trying to figure it out. i will rejet the carb, i'll go up two or three sized on the primaries.

Glen,you dont state anywhere in your post where your temp sensor is (head/intake) and if its an elec or mech gauge with temp sensor in head it will read approx 10 deg hotter that rest of motor due to close proximity to exhaust.

Also,if your running a mech gauge with metal temp sensor line it also gets heat soaked by ex heat driving temps up approx 5-8 deg on avg so insualte it from the head back to firewall which lowered the temp for my motor when i did that.

Timing,your 36 deg total is fine like you said but your intial still could be too retarded which will kill you temp wise at low speed/stop go traffic because the retarded initial timing will make the motor run hotter when the mech is not activated or not fully in,so check the inital at low idle speed with vac adv unhooked/plugged and set to a min of 16deg btdc with a non stock perf cam.

Lastly,If your running a perf cam set intial to approx 16-18 deg and then if your total is over 36-38deg(tops) have the mech advance recurved/limited to allow for the 16deg intial to get 36-38 total and things should be much better.

Now if your plugs are still running lean/white then check for vacuum leak and if ok then look at your prim/sec jetting and try going up a couple jet sizes in each end of the carb as a starting point for dialing it in.

But keep in mind i am assuming your not running too hot of a heatrange sparkplug which can give you false fuel calibration readings .

Scott

scott,
i am taking the temp on the intake, right by the thermostat. these aftermarket heads aren't even ported for a sending unit. also, i'm running a elect autometer gauge that i trust since it was about $80 by itself. not that it couldn't be wrong, but i wouldn't think so. now, correct me if i'm wrong, but i think the coolant would HOTTER at the thermostat than at the head since it's measuring the coolant after it's fully circulated and ready to leave the engine. i.e. i assume the thermostat is placed where it is because it needs to be where the coolant is the hottest.
the cam is a comp cams with .555 lift and 230/236 duration at .050 lift, and i think the initial is about in that 16-18 range, but i was mainly interested in the total advance. it actually seems to run cooler idling.

Does your car have a lean surge at cruise? The mixture at cruise should be much leaner (around 15:1) compared to the 12.5:1 or so you want at full power. Your plugs will be colored much lighter from cruising than from a WOT run.

The temperatures in the head will be higher than the manifold because this is the source of the heat. A sensor in the head is getting heat directly from the metal, which is hotter than the coolant. Once the coolant arrives at the manifold, it mixes with all the other coolant, some of which has taken a cooler route back.

I have had two 427 cars and both ran 210-220 and they never over heated. I know you always have your eye on the temp. gauge when you have a big block Yes take me to heaven in a 427. 82 year old machine down the road said to me one day ,do you know what radiator caps do For every pound of presser you raise your boiling point by 3 degrees So if you have a 15 pound cap you raise your boiling temp. by 45 degrees So 212+45=257 and both of my cars was red lined at 250. He said take your eyes of the temp. gauge and look at the women and enjoy your car

GLEN
Theres alot of good post here .
my feeling is number one ,the motor is still tight number two .. you may want to richen up the mixture till broke in .
mumber three ... I dont carE what brand gage anybody uses ... I still like i/r gun , to check against it .
example ... hit the the therm housing to see if it compairs with the gage ... then hit the top tank ... take a reading ...then the bottom tank .. you should see about a 30 degree drop in temp .
let me know your results .
Don

Glenn,get a hold of an ac thermometer that automotive ac tech's use which goes up to 220deg f.

Then get your motor heated up and check the coolent temp circulating/pumping out of the upper rad tubes by placing the end of the gauge into the stream of coolent while its pumping throught the core.

Maybe you could have someone hold the throttle at approx 1500 rpms to pump a nice stream of coolent over the end of the thermometer.

This is an easy/quick way of checking your coolent temp to see if there is a big delta between what you new gauge says opposed to whats pumping accros the upper tube/s from the thermostat which should be the hottest as you said.

If you motor is not actually forcing out coolent like its overheating and acting like its too hot loosing power then possibly the new elec temp gauge/sending unit is def or out of calibration.

I have found in the past that elec temp gauges/sending untis are more likey to not read as accurately as a good mech gauge but again that was my exp only.

If your running 16-18 intial it's fine but you do say your not that interested in the intial but it can make a motor run hotter if too retarded but thats not your case.

So check your coolent temp at the radiator fill neck when the elec temp gauge is reading real hot to see if the gauge and thermometer come close to each other like within 5 deg tops since your lelec temp sensor is by the stat housing by where the hot coolent leaves the motor on the way to the top of the rad.

My mild 396(now 402) with a highflow 180 deg stat runs approx 195-198 on a 85 deg f day while crusing (60-65mph) and up to 205-210 in std stop/go traffic. But if i am in real bad traffic it will go to 215-220 after 10-12 mins of being at a dead stop and then i start to get ANTZY looking for a way to get moving again ASAP.

I figure i can conservatively subtract approx 5-8 deg at any one time from the temp reading becasue my temp sender is in the head by the ex which falsely drives the temp up so a 210 on the gauge no looks better at 205 or 202 deg f . Some people say you need to subtract 10-15 deg when running the temp sender in a BBC head. But i feel i am being realistic/conservative in sub only 5-8 deg for sensor in head.

My mech temp gauge sensor is in the head by the ex port/manifold which does drive the temp up a little higher then the rest of te motor sees.

My car is a mild 396 with approx 370hp,4spd,331 gear,25 yr old 4 core rad with only 4-5k miles on it,stock 7 blade fan & std (not H/D) fan clutch,stock shroud,and a Milodon hi flow water pump.

My motor generally runs approx 15-18 deg above the 180 stat rating before you sub the 5-8 deg for temp sensore in head .

Let us know how you make out and what the temp reading are in the rad filler neck when hot.

Scott

took about a 25 mile drive...do other people experience their cars running warmer on the guage than the thermostat opening temperature? i have another car that runs about 10-15 degrees hotter than the therostat setting all the time, even on mild temp days.

Sure. The thermostat's function is to set a lower limit for engine operating temperature in the interest of engine wear and fuel consumption. A 180 degree thermostat is not designed to be full open by 180 degrees, or to regulate coolant temperature at 180 degrees, for example. I don't have a GM manual handy, but I have a '72 MOPAR manual in my hands. For a 185 thermostat, the temperature of the water in which it is immersed should be 182 to 189 when a 0.001 inch feeler can just be inserted into the valve opening. The thermostat should be fully open at approximately 210 degrees. So if the same situation applies with GM systems, your thermostat could just be cracking open at 194 degrees and be within spec.

My own humble opinion would be that many people here squander $$$ on cooling capacity they will never use with these expensive radiators and water pumps, and they obsess over temperature issues needlessly. But thats just one old geezer's $0.02.

This is useful info IMO... http://www.troubleshooters.com/toverheat.htm

I think I have posted this info before but I'll say it again just for discussion sake :

Water boils at 212*F at sea level. For every pound of pressure you apply to that water you raise its boiling temperature by 3*F. If you have a 14# pressure cap on your system that means you will NOT get any steam voids in your cooling system until the coolant temperature reaches 254*F. Hot water won't hurt your engine. Steam voids will. Steam in your engine is a lousy heat conductor.

If your car runs at a consistant 205* to 210* and you have the system properly pressurized then you have lots of margin before steam voids develop. As long as steam voids do not develop your cooling system will handle pretty much whatever you hand it.

Lord knows the engine sure doesn't see 20 or 30 degrees over normal for whatever period of time.


incidently with respect to water boiling at 212*F...no matter how much heat you apply to the water it will NOT exceed 212*F. It will begin to boil off into steam but if you stick a thermometer into a pot of boiling water the thermometer won't exceed 212*F no matter how long you boil the water.

To show how exterme this pressurized water thing can be , at the nuke plant I work at the reactor coolant system operates at 2250 psig and Tavg is 553*F @ 100% rated power. (Tavg = Temperature difference between cold water going into the reactor and hot water coming out)

Normally that means the water is "sub cooled" at 43*F. In other words sufficient heat would have to be added to raise the water temperature another 43*F before steam voids would begin to form in the RCS. That would be bad:)

incidently with respect to water boiling at 212*F...no matter how much heat you apply to the water it will NOT exceed 212*F. It will begin to boil off into steam but if you stick a thermometer into a pot of boiling water the thermometer won't exceed 212*F no matter how long you boil the water.

This brings up a interesting point ... with the rad cap off you will steam or boil over at 212 degrees
like a presure cooker on the stove cooking chicken .. by adding the weighted steam controler . that has weighted settings you increese boiling point ... its the same thing with your presure cap on the rad ... in laymen's terms .
so the cap will keep the steam pockets out of the engine .... you will not boil over till a higher temp as stated .
the cap will do nothing to keep temps down ofcorse .
you just wont puke as soon .

Good job on the post by the way ... I dont think any body knew that no matter how long you boil water it will not go beyond 212 degrees inless presurised by the lbs rating of the cap .
Don

thanks for the info guys, good stuff. i'm going to jet up the carb a couple sizes tonight and recheck initial timing. QUESTION for DON: i got a cap for your radiator from OPG which is kind of a repro of the original GM cap. it doesn't have a pressure rating on it. i did notice that it puked out some coolant after i killed it a couple times. but it could just be that i overfilled it last time i topped it off. should i get a different cap? also, i want to put a coolant overflow can in, like the long alum tube type, is there any science to the placement of this? i.e. the placement height, position of the line going to the radiator?

are not calibrated exactly, neither are temperature gauges

I guess in my case my parts weren't calbrated. Once the temp got to 180, my gauge almost always read within 5 degrees of the setpoint (180). Most of the time it was right on the thermo setting. That was my experience.

GLEN,I RUN THAT SAME REPRO RAD CAP WITH NO PROBLEMS OR PUSHING OUT COOLENT EVEN WHEN THE MOTOR HITS 225-230 DEG F WHEN IT HEAT SOAKS AFTER SHUTTING IT DOWN ON A HOT DAY.

Ops,sorry about caps.

That repro cap is supposed to be rated 15lbs so if your pushing out fluid your rad is either too full as you stated or your running on the edge of overheating and and when you shut it down and heat soak high enough to boil that pushes out coolent.

Scott

thanks for the info guys, good stuff. i'm going to jet up the carb a couple sizes tonight and recheck initial timing. QUESTION for DON: i got a cap for your radiator from OPG which is kind of a repro of the original GM cap. it doesn't have a pressure rating on it. i did notice that it puked out some coolant after i killed it a couple times. but it could just be that i overfilled it last time i topped it off. should i get a different cap? also, i want to put a coolant overflow can in, like the long alum tube type, is there any science to the placement of this? i.e. the placement height, position of the line going to the radiator?

As the system from factory was a closed system ... meaning there was no recovery system .. and the cap was a one way unit ... meaning if it puked it went to the ground , no catch can ... this means you should leave some room for expansion.. do not fill to till its over flowing .
If you change to a recovery system you will need a two way cap .. that will syphon fluid back .. in that case fill the system and some in the over flow tank .
location of the tank ... close by would be good lower then the cap i would suggest .
Don

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about the cap. I put a new cap on my 427 once that I got from the Chevy dealer and every time I stop the car ,it came out the overflow . I bought an original cap and it stop it