NEED A CHALLENGE? HELP ME WITH MY HOT RUNNING 396. [Archive] - Chevelle Tech

: NEED A CHALLENGE? HELP ME WITH MY HOT RUNNING 396.


SWHEATON
Aug 21st, 02, 2:52 PM
My Problem seems to be solved so thanks to all for your help,i tries/tested your suggestion out which lesd me to a solution..
There were 2 things that seemed to cause the car to run hot.

Fisrt was i have a mechanical temp gauge that has the std metal wire lead which i routed from the dr/side head in the stock position through lower portion of the valve cover bracket over the exhaust manifold which turned out to be the wrong thing to do.

I used to run the temp sender wire away from the head/motor not in the stock position over the ex manifold prior to rbld and thought that possibly the meatl mechanical temp sender wire was picking up too much heat from the ex manifold so i re-routed the sender wire away from the exhaust like i was priro to rbld.

This dropped the temp approx 8 maybe 10 deg which was a good thing. The stock sender was electric so the exhaust manifold was not an issue with that setup.

The second thing was the a suggestion i got reminding me that rblt motors do run hotter durring breaking due to higher interanl friction with rings breaking on tight fresh rebores ,etc . After driving the car around for 50-60 miles the temp dropped a few more degrees and now holds staedy at 195-200deg at speeds like 40-60mph so i think that's ok for a big block. If not let me know. I have not got into traffic yet to see how it does with the new clutch fan,time will tell.

thanks.

MOTOR IS A MOSTLY STOCK 69 396 OVAL PORTED' CAST IRON INTAKED/Q-JET & CAT IRON/FLOW MATSER EXHAUSTED STREET SHOW CAR I HAVE OWNED FOR 24 YRS.

I COMPLETELY RBLT THE MOTOR TO THE TUNE OF 4K
AND AM RUNNING THE SAME APPROX MILD PERF CAM AS PRIOR TO RBLD. I WAS RUNNING 10:25:1 COMP PRIRO TO RBLD,NO HAVE FORGED 9:7:1 COMP.

CAR RUNS HOT,UPPON STARTING IT TAKES APPROX 4-5 MINS FOR STAT TO OPEN AND GET TO 180 DEG.
THEN WITHIN ONLY 5-8 MINS (WITH THE HOOD OFF THE CAR ) IT GOES UP TO 210 THEN QUICKLY TO 230 WHERE I SHUT IT DOWN. VERY STARNGE THING IS IT NEVER SPITS ANY COOLENT OUT OF THE OVERFLOW LIKE IT SHOULD AT 230 WHEN I HAVE SEEN CARS DO THIS HITTING 220 AND UP. I MUST HAVE A GOOD SYSTEM THAT WONT LET IT BOIL OVER DUE TO HIGHER PSI = A HIGHER BOIL TEMP. RIGHT AFTER SHUTDOWN WHEN IT WOULD HEAT SOAK TO 240-250 FOR A COUPLE MINS IT WOULD STILL NOT PUSH ANY COOLLENT OUT AND I KNOW THE RAD IT FULL.

* I USED ARP THREAD SEALER ON MY MECHANICAL TEMP GAUGE WHERE I USED RTV PRIOR TO RBLD,IS THERE A HEAT TRANFER ISSUE WITH THE MECHANICAL GAUGE USING THE ARP THREAD SEALER? THE GAUGE WAS FINE PRIOR TO RBLD AND TEMP READINGS WERE NORMAL.

* BEFORE THE RBLD THE CAR WOULD NOT GO OVER 200-205DEG MAX IN THE SAME TIME PERIOD SITTING IN THE DRIVEWAY WHILE WORKING ON IT.

*CAR HAS THE STOCK ORIGINAL WATER PUMP FROM 69 RBLT WITH THE SUPPOSEDLY GOOD PUMPING CAST IRON IMPELLER IT CAME WITH. THIS PUMP WAS NOT ON THE CAR PRIOR TO RBLD,A STD AFTERMARKET SEALED POWRE PUMP WAS ON THE MOTOR. IS THERE A WAY TO CHECK/TEST WATER PUMP OUTPUT/PSI ON THE CAR? IT SEEMS TO PUMP THE COOLENT OK OUT OF ALL 4 RAD TUBES. AT APPROX 1500 RPM THE COOLENT WILL PUMP OUT OF THE TUME APPROX 1/2-3/4 OF THE WAY TO THE OPOSITE SIDE OF THE TANK BUT DOES NOT HIT IT IF THAT GIVES YOU N IDEA OF HOW THE PUMP IS FUNCTIONING.

*THE 4 CORE RADIATIOR WAS CLEAN BUT I STILL HAD IT ACID DIPPED AND CLEANED AN THE RAD SHOP SAID IT WAS IN GREAT CONDITION. I REPAINTED IT WITH SPECIAL RADIATOR PAINT FROM EASTWOOD PRODUCTS THAT SUPPOSED TO BE NOT TOO THICK AS TO OSBTRUCT AIR FLOW OR THE ABILITY FOR THE RADIATOR TO DISAPATE HEAT.

*THE FAN CLUTCH IS NEW (STD NOT HAVEY DUTY) AND THE FAN IS A NEW GM 7 BLADE REPLACEMENT.

*FAN SHROUD IS STOCK GM.

*NEW 180 HIGH FLOW STAT WHICH IS SAME AS I RAN PRIOR .

*AS FOR THE INTAKE,I DID RUN THE GM OIL SLASH SHIELD UNDER THE INTAKE AND ALSO USED THE EXHAUST CROSSOVER SHIELDS THAT LIMIT THE EX GAS GOING THROUGH INTAKE TO KEEP IT COOLER FOR MORE HP. I THOUGH DOING THAT WOULD JUST ENSURE ALL THE EX GAS GOES OUT THE EXHAUST TO KEEP THE INTAKE COOLER WHICH SHOULD NOT AFECT ME HERE.

* SAME DIST/ADVANCE ETC.

* SAME STOCK Q-JET.

THIS ONE HAS ME REALLY STUMPED. I HAVE MANY YR'S (30+ )REPAIRING/WORKING ON MOTORS AND EVERYTHING CHECKS OUT BUT THERE IS STILL A PROBLEM.

SCOTT

[This message has been edited by SWHEATON (edited 08-26-2002).]

Randy Mosier
Aug 21st, 02, 4:12 PM
I'd look for something outside of the cooling system. Perhaps you have a vacuum leak that's causing the engine to lean out and it's gone undetected. The sealer on the cooling temp probe should be fine. But fresh engines do tend to run a little hot sometimes, especially if the clearances are on the tight side. You might want to try switching to a 195 thermostat. It allows the coolant to stay in the radiator a little longer once the engine is up operating temperature, and thus, more heat is shed before it returns to the engine. Sometimes, there's such a thing as having a thermostat that's too cool. Give that a try, after you've determined that there is no vacuum leak or other condition that would cause the engine to run lean.

And this is just out of curiousity. Is the exhaust system in good shape? I have seen situations where critters crawl into a pipe and build nests, and sometimes wasps will build those mud nests inside pipes while the engine is out of the car. That's a long shot though. Check the other stuff first.

[This message has been edited by Randy Mosier (edited 08-22-2002).]

Whittaker
Aug 21st, 02, 4:12 PM
I fought this on my 66 with a 454. I went through several waterpumps and two radiators. I now have a huge grifen radiator that fits and looks stock. I also have a 7 blade straight pitch fan and a shroud. Every one I talked to saidd 210-220 is completly normal.




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1966 Chevelle Malibu Sandalwood, Gold color
454, .30 over, dual quads
700 R4 transmission
12" disks up front and hope to have disks in the rear soon.

chev64
Aug 21st, 02, 6:19 PM
Scott, Please don't type in all caps, it is hard to read and is considered shouting in internet speak.

Good luck with your heating problem.

------------------
Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club (http://www.chevelles.net/mcc/mcc.htm)

DjD
Aug 21st, 02, 7:04 PM
You haven't said if this happens running down the hwy or just sitting or both.. What is your initial timing set at? You should be able to KO a overheating problem with stock cooling parts.

------------------
...Dennis
The '69 (http://chevelles.com/showroom/ww.jpg) & the '96 (http://www.camaroslimited.com/graphics/memcars/96ss.jpg)
Team Camaro (http://www.camaros.net)
Camaros Limited (http://www.camaroslimited.com)

SWHEATON
Aug 21st, 02, 7:08 PM
SORRY ABOUT THE CAPS LOCK GUY'S,I WILL TRY TO
REMEBER TO TURN IT OFF.

ALSO,THANKS FOR THE SUGGESTIONS THUS FAR ON MY MOTOR RUNNING ON THE HOT SIDE,I WOULD APPRECIATE ANY MORE IDEAS ANY OF YOU COULD HAVE ADD TO WHATS ALREADY BEEN WRITTEN ABOVE.

THANKS....SCOTT

SWHEATON
Aug 21st, 02, 7:22 PM
PHEW I FINALLY REMEMBERED TO KILL THE CAPS LOCK.

Just a little more info to add to my original note for assistance for my warm 396.

The motor started up very quickly with no leaks,clicks/ticks/or taps from the valvetrain,good oil psi,40psi @ hot 900 rpm idle/502 @ 2k rpm (std psi spring in pump) with 10-30 oil for the intial cam breaking period,and the bottom end was quiet too.
The motor sounds and runs well with the mild street cam which is a comp that specs to 222/226 @ .05,.525/.525,with 112 lobe center and i also am running the comp magnum roller tipped rockers with mag pushrods.

acowboy
Aug 21st, 02, 11:51 PM
sure sounds like bad pump or temp guage to me.....is it really that hot at the radiator??

mr409
Aug 22nd, 02, 7:41 AM
Did you leave the radiator cap off until the stat opened for the first time? If not, you may have an air pocket. My 409 did that on fire up day and scared the hell out of me! http://www.chevelles.com/forum/eek.gif

It too spit water out too. (note-not coolant as you should only run water during the break in)

------------------
Bob (Pa.)

1963 Impala 283
1966 Chevelle SS 409
1969 Malibu 307
1972 Malibu 307
1969 C10 stepside 350
1971 Cheyenne 20 3/4 ton
Somebody stop me... :)

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ss3964spd
Aug 22nd, 02, 6:24 PM
Scott,

As Randy mentions, your temp sender should be ok with the sealent but the company that recalibrated my temp gauge to my sender specifically warned not to use sealent on the threads as it may compromise the senders ground path.

Secondly, since the 396 is spec'd basically the same now as it was before the rebuild, with the exception of the water pump, certainly the water pump would be suspect. But before you reinstall your old Sealed Power unit, just get yourself a handy dandy meat thermometer, remove the rad cap, and drop the MT in there - making sure the coolent level is high enough so the end of the MT is submerged. Start 'er up and let it run. Should give ya a good indication of if it's really getting that hot or if your gauge is not reading correctly.

Dan

------------------
Awww, fer cyrin out loud, there's that IMPALA guy again.

http://photos.yahoo.com/bc/ss3964spd?d&.flabel=fld1&.src=ph

a36chevy
Aug 23rd, 02, 12:18 AM
Rule of thumb for cooling systems also is for every pound of pressure created by the cap you gain 3 degrees over boiling point.

Xtreme70SS396
Aug 23rd, 02, 9:03 AM
The simple things can sometimes cause the most grief because you don't think about them - I would check your thermostat first. Make certain it is on facing the right direction, make certain it has one or more small holes for coolant bypass (gets rid of air pocket), and put it in a pan of hot water and make sure it opens at the temp it's supposed to.

Good luck.

HOTRODSRJ
Aug 23rd, 02, 9:41 PM
It's important to answer DjD's question about the overheating sitting and how about moving or cruising?

Where is the location of your sensor? Do you have headers too? There is a reason I am asking that.

Radiators overflow due to pressure, not temperature. Just thought I would throw that in.

If it cools going down the road at 30mph, then the fan system is the issue. Are you sure that the clutch is working properly. It is important that you KNOW this. Otherwise you make wrong assumptions going forward.

If you are sitting in traffic and it maintains 220 in the worst conditions, this is acceptable.

I would dump your stock pump. They are junk compared to todays high performance pumps.

DjD is right. For the most part you should be able to cure this with just about everything stock. However, things change with age. Blocks become more resistant to flow due to build up, people add hp building goodies which in turn produce more heat, even at idle. Clutches are not the products that they used to be when made by GM. They are very inconsistent in behaviour in my experience and I have replaced more clutches on stock cars with ones that readily fail.

Just some things to ponder. Check out my cooling forum listed below in the sig.

------------------
Steve Jack
-Concept One Pulleys and Brackets
-Marketing Technologies Limited
-Northern/Southern Rodder Magazine's "Jack'Stands" technical column author/originator

Metalmechanic
Aug 24th, 02, 1:47 AM
can you borrow a heat gun? check temps. at upper and lower rad. a 20 deg. drop would be ok. coolent flow prob? rag left in rad. inlet or outlet, temp gauge good? thermostat or waterpump, I would verify the temp. I would check temp drop across rad. an outside sorce could be creating the overheating problem, overfueling, ext. I would probebly change out the 6 doller thermastat and recheck.

SWHEATON
Sep 13th, 02, 6:31 PM
Hi guys,thanks for all the suggestions. The motor run cooler now that I have put 150 miles on it,i guess it was tight with the new bore resulting in more friction & heat.

The car now runs on a 90 deg day at 195-200 at 30mph and above and in normal upper N.Y.S. stop /go trafic it hits 205.

If it let the car sit still in the driveway for 5 mins at approx 1500 rpm the mech gauge in the car says 210 but the coolent temp in the radiator with the cap off reads 185. This seems to me like these temps are ok but they are on the edge of acceptable and if they were to go higher would be a problem,what do you think?

Is this 20 deg delta normal from where the mecahnical temp gauge sending unit is in the head by the exhaust to the actual coolent temp as read through the open radiator? I was able to verify the 185 deg coolent temp at the open radiator neck with 2 dif thermometers so i know thats correct.

Scott

PUUU70
Sep 13th, 02, 8:29 PM
When I rebuilt my 402 I had a temp problem too.It turned out to be the electric sender for the temp gauge witch is mounted in the head. I went through about 5 of them till I got wone that worked right. It also turned out to be a A C Delco one that worked. Good luck.

Tom Mobley
Sep 14th, 02, 10:25 PM
Keep in mind that a typical modern car with electric fan is set up to turn on the fan at 230. This is a normal operating temp. Down around 200 is great. Key is, will it hold a consistant temp or does it just keep climbing until it blows the pressue cap pukes water on the ground? The actual temp
is less important than it's stability.

IMHO, YMMV, all that jazz, Tom