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Upshift rattle...

1830 Views 9 Replies 5 Participants Last post by  Nahs
Hello all, I have a problem with a rattle from my engine compartment when my transmission is upshifting during hard acceleration. It has a stock 305 with a performer intake and 600 cfm edelbrock carb and headers added. I talked to the previous owner who added these items and was told that he had bought it that way. The engine runs and idles great with no other problems other than the rattle. It almost sounds like lifter noise but I am no mechanic. I have had several people tell me it may be valve noise or possibly lack of oil pressure. The engine does not run hot (added a 3 core big block radiator) and has a idiot light for oil pressure which I have never seen come on except at start up. Any help would be greatly appreciated.
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Where is the timing set? If it is just a little too advanced, you will get some clatter on the upshift. I think that maybe if the eddy is too lean on the secondary curcuit, it could also cause a clatter on the upshift.

Randy (couple things to check):)
maybe a wristpin? Under hard accleration, could be several things. Could be the pigmys trying ta get out.:)

Try running a tank of the highest octane gas you can find. If that solves the problem, then it is detonation and needs to be addressed by a competent tuner. It might be a little lean with the headers. Is the egr setup still working ? That is one of the primary functions of the egr system.. to suppress detonation.
what year is the vehicle ???
Sure sounds like detonation. May be a little lean at the rpm it shifts back to or more than likely too much advance at the point for the load on the engine.
It is a 1978 Nova Custom with a Edelbrock Performer intake - no EGR.
Does that help?
The "No EGR" helps a bit. Did you check the timing?

Randy (timing is the best place to start):)
I am going to try that this weekend, thank you for everyones input. I'll update soon.
Thanks for everybodys help the timing was advanced by 8 degrees. I reset it this last weekend and its quiet as a sleeping baby.

Thank again...
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