Pontiac people, random noise coming from my newer 400, I have no idea what it is

DarkoStoj

DarkoStoj

A mysterious figure named Darko
bought a 78 trans am with a 400 and the guy didn't know much about the car, but he did say the motor, transmission, and rear axle only have a few hundred miles on them.

Here are the specs
I think around 10-10.5:1 compression with forged pistons
62 heads
1.65 roller rockers
RAIV camshaft
edelbrock performer intake
holley 750 3310
solid motor mounts

The noise sounds like a clunking noise, and it sounds like its coming more from the passenger side than the drivers. It almost sounds like the exaust is hitting somewhere on the motor. The noise is completely random and doesnt have any regularity to it.

I put a long screwdriver on the intake and put my ear to it, and it definately doesnt sound smooth at all. The guy who built the motor (guy who owned it before the guy I bought it from) said he might have put the camshaft in more advanced or retarded than he should have, but he wasnt sure. Also there is low oil pressure when the motor warms up, I'm not sure if the guage is correct because it is aftermarket and the motor is newer. I have no idea though. I pulled the valve covers and everything looks good. I think I'm going to pull the intake and cam out to check and see how they look. Any thoughts or ideas on what the noise could be?
 
If it's irregular or intermittent, it's probably not in the engine itself. Maybe a
broken motor mount, or exhaust clank. Does it happen when you nail the car, put in in gear, when? I'd be a little concerned about low oil pressure. How low
is low? You should have higher pressure when you first start the car, then it should lower a little as the oil heats up and thins.
 
mls48341 said:
If it's irregular or intermittent, it's probably not in the engine itself. Maybe a
broken motor mount, or exhaust clank. Does it happen when you nail the car, put in in gear, when? I'd be a little concerned about low oil pressure. How low
is low? You should have higher pressure when you first start the car, then it should lower a little as the oil heats up and thins.
Click to expand...
it has solid motor mounts, they aren't broken.

i can hear and feel it when the car is idling. I'm not sure if it does it when the car is at a higher rpm because the exaust is so damn loud.

The pressure is high when I start it, but when it warms up it drops to ~0-5 at idle
 
put a new mechanical gauge on then look..also what oil are you running..i personaly run valvolive 20-50..in the hotter summer months....in the begining and end of summer i run straight 40



JACKO
 
Check your trans mount, the trans to block bolts, and the torque converter bolts. Check for clearence around the headers thru the sub frame

Advancing or retarding the cam wont make noise, just change the power band of the engine up or down.
 
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