Visit The Dirt Forum for More Information

Author Topic:   Cooling system help needed
teamnofear
Dirt Roller

Total posts: 12
posted September 07, 2004 08:41 AM  
I run 383 Chevy engine running on Alcohol. The last few races, the motor has been building quite a bit of heat. It reaches 200 or so when idling for 5 minutes and 240 within 6 laps or so of racing.

First thing I changed was the radiator cap. It didnt help.

I then removed the thermostat and replaced it with a old thermostat with the guts removed (about a 1" diameter through hole). At the same time, I also up-jetted from 92 to a 96 Pill. And again it still built heat. I did notice tthere was a pretty bad exhaust leak from the #3 & 5 Cylinders so I fixed that as well. I leaked the motor down and all but one ccylinder looked good. Either 3 or 5 leaked 48% the first time. I used a mallett to tap the valves and turned the motor over again. This time it leaked about 22% which is still high, but I assumed there must have been some debris on one of the valves or something.

This week during hot laps, the car kept popping or backfiring on the left side and again the temp got up to 200. It still turned pretty decent RPM though. I changed plugs and upjetted again to a 98 pill. The plugs I took out looked pretty good, but maybe a slight amount of white to them.

During the heat race, the miss was gone, but 3 green flag laps and 8 caution laps sent the temp up to 240 again. The radiator and hoses seemed to have quite a bit of pressure in it so i dont think I have a cooling leak anywhere.

It was blowing quite a bit of steam or whatever through the valve cover breathers. When it cooled and I turned it over with the starter, it was puffing through the valve cover breathers. Is this normal?

Oil looked a little milky, not sure if its alcohol or moisture. Fuel pressure is about where it has been all year - belt drive pump (2-3 at idle, 10-12 at speed). Oil pressure looks good. No smoke was coiming out of headers either that anyone noticed.

What should I check next??? Do Aluminum radiators "wear out "of become clogged? if so, how do you clean it? I run GM 4 blade fan 1.5" from radiator. Should I look at water pump? Bearings still seem pretty good on it. I beleive I have a 1:1 reduction pulley system. I want to re-check the leak down and valve lash again. Could my carburator be causing the problems? If so, what can i do to fix it? I am still not sure I have a good exahaut header either? Would this build heat if it was leaking or cracked?

Any other suggestions or ideas? Thanks.

norightturn
Dirt Maniac

Total posts: 159
posted September 07, 2004 08:49 AM  
Check your radiator. I have seen motors run hot and swell the tubes closing off the air flow through them.

hamer36
Dirt Maniac

Total posts: 196
posted September 07, 2004 05:57 PM  
with the radiator cap off, check that the water pump is circulating the water. I once had the pump impeller loosen and quit pumping.

dirtracer14
Dirt Forum Champ
Total posts: 1261
posted September 07, 2004 09:35 PM  
I would look at 3 and 5 again....back the rockers off and put air in the plug hole and see if it leaks!!!

fastow
Dirt Maniac

Total posts: 168
posted September 07, 2004 09:45 PM  
my moneys on cracked head

racer2
Dirt Freak

Total posts: 352
posted September 08, 2004 06:46 AM  
ill second that

teamnofear
Dirt Roller

Total posts: 12
posted September 08, 2004 07:18 AM  
Thanks for your help so far.

I pulled the heads and head gaskets looked great. It appears something may be going on with the valve in my #3 and 5 Cylinders though. They still ahad 22 and 18% leakdown repectively. It appears I may have had a leak on the bottom side of the header between these cylinders where the header mounts to the head. One of the tubes in the header was really white while the others looked normal. The oil under this valve cover was really milky or creamy. I suspect I may have a valve issue caused by the leaking header so I am going to take it in to have it checked out.

Also, I pulled the plugs again and they were all pretty dark except for the # 3 and 5 again.

Since I have the radiator out, is there a vay to check this or flush it out?

Is there anything else I may want to investigate as well.

Again thanks for all of your help!

autoshop
Dirt Freak

Total posts: 298
posted September 08, 2004 08:49 AM  
Mag the head , pay close attention to the area at the lower coolant hole between the cylinders at 3 and 5 . I bet that there's a crack in the water jacket between the two cylinders. It pretty common in the chevy heads.

teamnofear
Dirt Roller

Total posts: 12
posted September 08, 2004 09:09 AM  
I have Bodix aluminum 23 degree heads. Is the cracking still a problem with them?

autoshop
Dirt Freak

Total posts: 298
posted September 08, 2004 12:57 PM  
They crack at the two center lower headbolt holes, Right in between them. kinda in a half moon between the bolts hole on the outside of the head. that also where the biggest water hole is.

teamnofear
Dirt Roller

Total posts: 12
posted September 09, 2004 12:25 PM  
Thanks for all of your help. I think I finally found the root cause. I found a crack in one of the cylinders. Water was not getting in the cylinder that I could see, but I suspect as the motor warmed up, the crack enlarged and the hot combustion gas was getting into the coolant and the pressure was slowly pumping the water out of the overflow.

The heads did check out to be good though.

Back to the Archives