Engine noise

i have a 73 nova with a 350 in it. i bought it a few months ago and was told it had a rebuilt motor. besides the oil leaks, now when i accelerate the car and get into higher rpms i hear this knock/rattle/ping. I cant figure out what it is and now i just put it in the shop for 160 bucks for 2 hrs of labor, who can help?

First, where is your ignition timing set? Depending on which cylinder head you have, it should be about 8 BTDC "initial", with a total of 38, "all in" by 2,800 RPM.

Do you KNOW which head casting you have? It could be very important. Also, any other modifications to the engine? Please be as specific as possible.

If your timing is "good", put a few gallons of 110 octane race gas in there and see if the noise deminishes or goes away. If it does, you're experiencing detonation due to too low an octane fuel for the compression ratio. The only "fix" for this is to reduce the static compression (pistons or heads) or run race gas as a "steady diet" (illegal in most areas).

All of this is VERY destructive of engine parts, particularly pistons and rings, so don't keep driving it except to "test" the changes.

Jim

i have a 73 nova with a 350 in it. i bought it a few months ago and was told it had a rebuilt motor. besides the oil leaks, now when i accelerate the car and get into higher rpms i hear this knock/rattle/ping. I cant figure out what it is and now i just put it in the shop for 160 bucks for 2 hrs of labor, who can help?
Hi, Mr Horsepower, this problem is really simple to diagnose, and possibly even easy to fix. First off, you have a very easy motor (possibly the easiest) to work on; fix and build...

Is the sound coming from under the vavle covers, or the bottom end of the motor?

What all is in the engine compartment, do you have smog equipment (smog pump, pcv, etc.), power steering, etc?

I can help you, if you get back to me.

i cant tell if its from by the firewall or under the valve covers, it only makes the noise when driving. no smog equip or power steering. just a old school custom chevy rod. thanks for the help, its still at the shop, the guy dont know whats wrong with it either.

timing is good, not sure of the casting numbers, just bought the car about 5 months ago and only drive it back and fourth to work, they always put regular in it and i have and its driven fine until about a week ago. standard bolt on performance parts, nothing to much, clay smith cam, lifters, and the rest. thanks for the help.

I would be willing to bet that it's in the transmission, chances are, when the engine was rebuilt, nothing was done with the transmission, if I were you, if he hasnt figured it out, get your car out of there to stop getting charged for something that he hasnt figured out. Is the tranny a TH350?

That would be one of the only feasible explanations, sounds like it could be a problem with the front pump, or the torque converter.

what shape is on the front of the head? is it a camelback, half a triangle?, etc, etc...

Casting # Years
made Valve
Size HP levels
used for Chamber Size / Notes 3782461 61-70 1.94/1.50
& 2.02/1.6 250-375 64 CC Chambers
No bolt holes
These are the double humps. 3890462 62-68 1.94/1.50
& 2.02/1.6 250-350 64 CC Chambers
No bolt holes
These are also double humps. 3927185 69 1.72/1.50 200-210 70cc Chambers 3927185 69 1.72/1.50 200-210 70cc Chambers 3917293 68 1.72/1.50 210 76cc Chambers 3917291 62-69 1.94/1.50
& 2.02/1.6 275-350 64 CC Chambers
No bolt holes
These are the 'Turbo' heads. 3927186 68-72 1.94/1.50
& 2.02/1.6 290-370 64 CC Chambers
has bolt holes
These are the 'powerpack' heads. 3932441 67-79 1.94/1.50 250 & 255 76 CC Chambers
Intake flow 152 CFM
Exhaust flow 93.2 CFM 3947040 68-70 1.94/1.50
& 2.02/1.6 290-370 64 CC Chambers 3947041 68-70 1.94/1.50
& 2.02/1.6 290-370 64 CC Chambers 3973414 64-70 2.02/1.6 360 & 370 64 CC Chambers
Z-28 & Corvette LT-1. 3973487 68-79 1.94/1.50
& 2.02/1.6 165-330 76 CC Chambers
X casting has 10 more intake
cc volume. 3998993 68-79 1.72/1.50
& 1.94/1.50 115-175 76 CC Chambers
Intake flow 150.8 CFM
Exhaust flow 91.1 CFM 333882 70-80 1.94/1.50 150-180 76CC Chambers
Intake flow 137.2 CFM
Exhaust flow 95.4 CFM 462624 76-87 1.94/1.50
& 2.02/1.60 Not listed 76 CC Chambers
These are crack prone!

could be the tranny, I know for a fact that they did not mess with it when they did the RB. its a borg warner 4 speed. would a loose tranny mount sound like a motor mount knock, or would it make that rattle/ping/knock?

soon as i get it out I'll look at the heads, still on the same quote from yesterday, I dont think he is going to figure it out, I have heard this noise before and other cars, it almost sound like the oil dip stick ratteling around, thats the best i can describe it. thanx again.

could be the tranny, I know for a fact that they did not mess with it when they did the RB. its a borg warner 4 speed. would a loose tranny mount sound like a motor mount knock, or would it make that rattle/ping/knock?
It sounds as if you have a really easy setup, I do envy you in that sense, but what I really, really recommend, is to pick up a hughes manual and a chilton manual, not only for your car, but the motor it came out of... look at the block casting on the drivers' side of the block, in front of the bell housing, it should read something like :3970010= 350 chevy block, 4 bolt main... This car would be cake if it were sitting in front of me... I will do the best I can to help, but you really should begin to DIY... Power of awareness is priceless.

left the car at the shop, im gonna have him tear into the manifold, hooked a vacuum gauge up and it looks like there is a leak at the manifold or the gasket, the thing is that its getting into more depth then i care to in my garage, so another 3 or more hours of labor at 80 bucks an hour we will see after tomorrow. thanx again for the help, once i have a car back in the garage I can look into the number.