New noise from a new engine

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Well, it's not the TC bolts. They're all tight with no witness marks. Don't see any marks inside the distributor cap. Riser valve has been removed from the manifold. So now I'm leaning back toward an exhaust leak.

I'm a rookie engine builder, and I'm thinking maybe here's my mistake. I read that these 340 manifolds didn't use gaskets, but had the heads and manifolds machined flat for sealing. I didn't do that, and instead added a smear of copper RTV to the mating surfaces. A slight leak could explain why it took a few miles for the noise to appear, and it's varying intensity. Sometimes I can't hear it at all. Could be that I just need a good set of gaskets as Icetech suggests. What are those, anyway?
 
I used Remflex exhst gaskets on my 340. It's a long shot, but take dist cap off and rollover by hand, see if rotor is hitting the pickup? I had a new dist pickup that was fd up.
Does sound vary with rpm?
 
6T9QDA said:
Well, it's not the TC bolts. They're all tight with no witness marks. Don't see any marks inside the distributor cap. Riser valve has been removed from the manifold. So now I'm leaning back toward an exhaust leak.

I'm a rookie engine builder, and I'm thinking maybe here's my mistake. I read that these 340 manifolds didn't use gaskets, but had the heads and manifolds machined flat for sealing. I didn't do that, and instead added a smear of copper RTV to the mating surfaces. A slight leak could explain why it took a few miles for the noise to appear, and it's varying intensity. Sometimes I can't hear it at all. Could be that I just need a good set of gaskets as Icetech suggests. What are those, anyway?
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Since they come with gaskets from the factory and I have never read anywhere that 340 exhaust manifolds don't require gaskets, throw that article out.
 
Plug the exhaust to create back-pressure, hold cloths over the tailpipes, apply pressure, listen for leaks, - not rocket science.
 
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Post #15. If the reluctor contacts the magnet, you get NO spark & you would soon know because the engine will run rough & likely misfire.
 
Mean416 said:
It's always an exhaust leak right? Really.... it's not a Mopar if it doesn't have an exhaust leak or two snicking away
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Exhaust cut outs in the system fix that. No longer will you hear that darn tic, tic
 
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