Team Camaro Tech banner
Cancel
Create thread New Garage Forums

Another Over Heating 396

Jump to Latest
21 - 40 of 49 Posts
#22 ·
my rebuilt 396 with factory rad, aftermarket flex fan and factory shroud runs 2 bars down from the dead middle point on the factory gauge. Its a mild cam, alum intake and a eddy carb. my initial timing is 17 deg, running a factory vac advance, using a factory points ignition. timing is key...
 
Discussion starter · #23 ·
I am happy to report that after getting a new water pump from Summit along with an 18" clutch fan and a new 180 T-stat the beast appears to be running a lot cooler. I still need to check the timing and add the anti-freeze but the initial test run had the T-stat open with the gauge just above the middle and it held there for a bit. Then it began to climb because it was in the garage with no fan running in front. It never spewed this time and never pegged the gauge. I let it sit for about 5 minutes then started again and the gauge went down below half. I do believe that all the suggestions were spot on and I thank all of you who responded. Thank you Thank you Thank you.
Jeff
 
#24 ·
you mention high compression pistons, but how high?
i used to run 12.5:1 60 over and the heads cut .020 in my race car and i had heating problems untill i went to racing fuel . 115 octane i think.
my tempeture droped 30 degrees
 
Discussion starter · #25 ·
well after coming home from vacation I fired her up and reset the timing to 16 D before TDC then readjusted the mixture so it wasn't running so rich it burned my eyes. This heated it up quite a bit with running so long in the garage with no fan in front. Not to over heating but it did get to 3/4 on the temp gauge. I let her sit then took out for a test drive around a few blocks thinking that should cool her down.......nope she kept climbing and I put her back in the garage before it pegged the needle. She never puked but I didn't want to go there. It takes a lot longer for the temp. to come up but it just doesn't seem to cool down. Now I am totally baffled. I have no idea how high a compression piston was installed nor do I know the cam since the engine was built before I got the car. The idle sets nicely at around 800 so I don't think the cam is too radical. I do know the engine was bored .30 over because it was labeled on the piston head. I do run high test, 93 octane, in the car and it is fresh gas. I am about ready to give up. This is so frustrating! Any more suggestions?
 
#27 ·
JeffsSS said:
Is running a 600 cfm carb too small? Could this be causing the over heating issue? It has been suggest to me that I should boost to a 750 but I do not see the logic in that. Any thoughts?
Click to expand...
No, the carb won't change anything to do with the cooling.

Do you have vacuum advance on your distributor, and is it hooked to full manifold vacuum (below the throttle plates) ? That will add a lot of advance at idle and help it run cooler.
 
Save
Reply Quote Like Like
#28 ·
Jeff with those upgrades (water pump and Clutch fan) and you are running that hot, something is wrong! You will have to pressure test the radiator and see if it holds pressure. You stated that you had a previous blown head gasket!! I hope the block is not cracked??
 
#29 ·
i might of missed it…But have you installed a new gm rad cap?…i have had many cars come in with a overheat and found the rad cap faulty.


get a tester from a parts store that checks for hydrocarbons in the coolant..they are cheap
over heat at idle is the heat exchangers failure to remove the latent heat from the coolant, the causes are…coolant moving to fast, to slow, undersized componets for the task at hand, poor air flow at idle, incorrect ignition timing or a mechanical failure of some sort. lean condition. it seems that you have check most of them. ...
 
Discussion starter · #30 ·
Radiator cap is new at the same time as everything else. I know the rad. is holding pressure because it no longer pukes and even running as hot as it did today it did not lose any fluid. I doubt the block is cracked because there is no other signs to point to this. There would have to be water in the oil or some sort of sign and there is nothing. I am running an MSD system so no vac. advance. I did change the timing so maybe I will advance the timing back to 18 like it was before. I will also reset the edlebrock carb and start again with the mixture. Other than that i have no idea what could be causing the overheating problem. I know that timing and mixture are everything on these beasts. Any other suggestions?
Thanks, Jeff
 
#31 ·
you only run 18 deg at idle…that will induce heat…my mildly cammed new 396 (idles at 750 nicely when warm) runs a 16 deg vac advance and 16 deg initial. when my vac can failed it ran 2 bars higher on the factory temp gauge, i am going to try 18-20 initial and see how it runs..the cam i have is in the 224 range at .050, i cant remember the exact specs, but its a mild 10.1 engine…they need vac advance…

I also have a eddy carb on mine….
 
#32 ·
jeff just MHO I would pressure test the system to be sure. Right now its a guessing game. What radiator are you using??
 
Discussion starter · #33 ·
I will test the pressure. I am using a 4 row 23" aluminum radiator. I am using the MSD ign system and dist. so I do not have the vac adv. I currently have it at 16 deg at idle yes. that is initial timing which is what you speak of correct?
 
#34 ·
I'm not running vac adv either. I can idle all day long with the set up I suggested without issue. I do use a 160* thermostat. Yes I know the 160 to 180* thermostat is up for debate, the 160* always worked for me. I have to ask... The fan and clutch are installed correctly?
 
#35 ·
I hate to suggest this,,,,,, it's not an insult,,,, honest. Is the thermostat reversed? The spring goes down toward the engine.
 
Save
Reply Quote Like Like
#36 ·
A hi-compression 396 can get decent gas mileage if it has vacuum advance.

You really should try a different distributor and hook the vac advance to full vacuum. Even if it doesn't stop the overheating (I think it will) the gas mileage and driveability will be much improved.
 
Save
Reply Quote Like Like
#37 ·
JeffsSS said:
I will test the pressure. I am using a 4 row 23" aluminum radiator. I am using the MSD ign system and dist. so I do not have the vac adv. I currently have it at 16 deg at idle yes. that is initial timing which is what you speak of correct?
Click to expand...
That could be a major part of your problem; you need the vacuum advance, connected to full manifold vacuum (NOT "ported" vacuum), so it's fully-deployed at idle, adding about 15* of timing to your base timing setting.

The vacuum advance unit must be spec'd so it's fully-deployed at least 2" Hg. below your idle vacuum reading, so it's pulled solid to the stop at idle.

There's a "sticky" by me on this subject at the top of the page in the "Performance" forum; read it and it'll help you understand why vacuum advance is important for a street-driven car.

:beers:
 
Discussion starter · #38 ·
Thanks JohnZ I read your sticky about vacuum advance. Very enlightening and something to consider. I am getting tired of buying new parts to just shoot in the dark. The MSD set up came with the car so I am using it. I have read many post in here about people using the MSD system with no such problem I am experiencing. The Eddie 600 cfm carb is also new but I find little change when I adjust the mixture screws. The car runs so rich it burns my eyes in the garage. I can't seem to lean it out enough to stop this. Could this indicate another problem? the car has not been driven much because of the over heating problem so I wouldn't know much about the "driveability" If I change out the dist can I still keep the MSD box? What dist. would be good for me to get? And yes the therm is in correctly I did think of that also.
 
#40 ·
Mechanical fan,clutch, shroud and vac advance dist. WILL fix your heating problems if you know your stat and pump are working properly. There many distributors that will work with your box. Ask JohnZ , I'm sure he will steer you the in the right direction. You can try www.4secondsflat.com also. He knows his stuff.
A vac gauge sure helps when your new at tuning carbs.
 
21 - 40 of 49 Posts
About this Discussion
48 Replies
22 Participants
Last post:
DT
Team Camaro Tech
posts
2.4M
members
90K
Since
1998
A forum community dedicated to 1st generation Chevy Camaros owners and enthusiasts. Come join the discussion about performance, builds, restoration, modifications, classifieds, troubleshooting, reviews, and more!
Full Forum Listing
Explore Our Forums
Bench Racing Engine Body Shop Performance Brakes, Suspension & Steering