felo72

Guys, I really need help please. I rebuilt a 383 TPI engine that was originally in the car when I bought it. Before I rebuilt it, the previous owner didn't set the lash correctly and he just installed new lifters on an old cam! So it wiped out 7 lobes. Anyway, it had an overheating problem before, but went away a week before builtup. I started it tonight, reved it up and down between 2,000 and 4,000 RPM, per machinests request, and it went up to 260 degrees in 7 minutes! I turned it off, left the fan on and checked the fluid level after it quit boiling. I was fine on fluid, but the upper radiator hose could be squeezed together. So that's one thing I found. I let it cool down, rechecked the level of fluid, and started it up again, and the same thing happened. This time I could see the exhaust manifolds glowing. I though Oh sh-t, so once again I let it cool down, then thought to check the fuel pressure. It had an adjustable regulator on it and after I put the gauge on it it read 31 to 32 PSI. So I unscrewed it all the way, by this time I have some gas trickling out the top, and it only read 35 psi. I decided to call it a night and get on the web to get all of your opinions. Could the diaphram be bad in the regulator, causing the engine to lean out and overheat so bad? I checked all of the vaccume lines and they seem ok, and the timing is set.

Any comments or suggestions would be a great help.

ede

sounds like you have the timing set wrong

felo72

I checked it and let it idle down just to check it. If by chance I do have the timing wrong, would it still create the engine to heat up that fast? I mean really fast?

Mark A Shields

Possibly if you're runnin real lean, I guess.

felo72

I plan on changing the AFPR tonight. The diaphram is shot because i have fuel coming out of the vacuume line and out of the top of the regulator screw. I have one question though, what psi would be a good setting? It is a 383 TPI, I thought 45 would be sufficent. And when I set it, the car doesn't have to be running does it? Thanks guys for the help so far.

cp87GTA

Retarded timming will cause an engine to overheat real quick like that. You're better off with advanced timming during breakin. Running lean or rich will cause the same thing though. Did you drill an air escape in the thermostat? Could also be air locked.

ZZ28ZZ

In regards to being able to squeeze the top radiator hose; was that with a hot eng before you removed the cap?
If so, your radiator cap may be bad and not allowing system to pressurize. If there's no pressure, water will boil at 212*. With 15 psi of press, water boils at 257*.
Antifreeze will raise the boiling point slightly, but pressure is what makes the cooling system work.

Sounds like your on the right path addressing the low fuel press, but if the cooling system isn't pressurized by the time you hit 220* you should be checking/replacing that cap.

felo72

Thanks for the replies guys, I went home last night and changed the regulator and dialed it in at 45 psi with the vacuume gauge disconnected. Long story short, it was too much pressure, so I set it at 39 psi and the car ran great and the temp doesn't go above 170 degrees.