Overheating with Chevy 350...(long)
OK, I've checked through the archives and have tried everything I can think of, with no luck. I've worked as a mechanic for the last year and a half, and have never seen a problem like this. Before I pull the heads and check for a failed gasket, I wanted to solicit as many opinions as possible.
The pertinent specs on my jeep:
-'81 CJ7 with a NEW GM Goodwrench 350 ('69-85 truck engine)
-Weind water pump
-March serpentine pulley kit (not underdrive pulleys)
-Mepco 3 core heavy duty conversion radiator
-Flex-a-Lite dual electric fan (rated at 2700 cfm)
-MSD 8360 distributor and 6al ignition
-Edelbrock Performer intake and 600 cfm carb
-Stock Chevy "rams-horn" exhaust manifolds
-195 degree t-stat
-16 lb rad cap
-50/50 coolant/water mix with overflow tank
I've only put a couple hundred miles on the new engine, and have developed an overheating problem. The engine will idle at 200-210 all day long without overheating, but once I give it gas (even at a standstill), the temp rises slowly to 240-250. Keeping the throttle at the exact same position, the temp stays at 250 for about 3-5 seconds, then slowly falls to around 180, then comes back to 200-210, where it stabilizes. Eventually, the temp starts to rise again, while keeping the gas at the same position, and the process repeats.
Here's what I've done:
-replaced rad cap and t-stat
-replaced upper and lower rad hoses
-burped coolant system of all air
-adjusted carb mixture many times
-adjusted timing from 0 degrees up to 20 (detonation)
-installed new mechanical water temp gauge along with Autometer Phantom electrical gauge to verify correct temp readings
-replaced vac advance on distributor
-changed advance springs (all 3 sets)
-disconnected vac advance hose
-hoses do not collapse under throttle
-cooling fans will hold a shop rag on the front of radiator without falling
-looking down radiator, I can see the coolant moving
-changed spark plugs
I can't imagine I have a problem with the water pump, cooling fans or radiator, because this condition occurs even at outside temperatures of below 15 degrees. I'm not losing coolant and I don't have coolant in the oil or a sweet smell from the exhaust. When I put the intake on the engine (years ago), I did a stupid thing and used alot of blue RTV along with the intake gaskets, so I'm thinking of pulling the intake to make sure I don't have any blocked cooling passages. My next step will be to check the head gaskets.
Anybody have any suggestions at all???? This has been a 5 year project, with countless dollars spent...I hate to see it just taking up space in my driveway for much longer.
Thanks alot and sorry for the length of the post.