Hey guys ive got a 85 Trans Am with a recently swapped vortec 350 with, Stealth ram, cc503 cam, 1.6 roller rockers, and around 10:1 compression.
I used the exact same headers and exhaust on my 305 with no tock/knock. The exhaust isnt hitting anywhere that I can tell. I did have to do some major massaging to the y-pipe to get it to clear the oil pan on the vortec( its still extremely close to the pan). Could it possibly have something to do with the tune? Its a bit on the rich side but I dont think that would cause the noise. It also seems that the muffler really magnifys the noise. If i remove the muffler the tock/knock is much harder to hear. If anybody has any idea what it might possibly be let me know!

Heres a link to the video. Its kind of hard to hear the tocking in the video, Its most audible near the end.

 

1. Beautiful color of blue you have.
2. Why are your exhaust resting against the bottom of the rear bumper cover?
3. When doing exhaust work , I feel to make sure there is clearance for at least my fingers to pass between the exaust and the car's body and frame to allow to movement without rattling against anything.

 

I agree with MintWS6FORMULA. In the video, those pipes appear to touch the rear bumper cover. I didn't hear any "tock/knock" as you described. Sounded pretty normal to me.

 

Thank you I personally think its one of the best color combos for TA's. The exhaust is up against the bump cover because I like the look of it. Its actually just barely touching. Its been like that for 3 years now with no discoloration of the bumper or any other negative side effects.

Heres some pictures of the clearance. I only have space between the pipe and the pan to fit a piece of wire. I don't have any other clearance issues.

 

The noise is definitely harder to hear in the video. It could be described as a sort of popping noise. I never noticed it until my brother pointed it out to me and now its all I hear.

 

Try slipping in a piece of rubber or cardboard to isolate it for a test. That's probably not enough clearance. You can also go under there and thump the exhaust around and see if that's your noise.

 

[QUOTE=Joe Tag;5826205]Try slipping in a piece of rubber or cardboard to isolate it for a test. That's probably not enough clearance. You can also go under there and thump the exhaust around and see if that's your noise.[/QUOTE
Just tried that, it didn't make any difference. I wonder if all the hammering ive done has caused some restrictions that are producing the noise? it seems plausible.