My car starts "instantly", but clatters loudly a couple of times just as it fires off. Why does it do this? What, if anything, should I change to stop this?

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'87 IROC 5.7l TPI - original owner!

 

You sure it's detonation/preignition, or maybe it's the lifters rattling?

 

i'd suspect lifters or oil preasure problems at start up and not detonation

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

It's part of the Ignition system....I brought my car over to a mechanic thinking that it's only the timing on the car and no big thing actually....It was a big thing.....Don't let your car die.....bring it to a mechanic now before internally the engines crank will get messed and a rod may break while your driving it's very serious the engine just may sieze right up....I would advize putting in a whole new block.....

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IROC-Z
G92, LB9 305 TPI, 3.23

 

It's louder than lifters or anything like that. You ever heard an engine that's running on - dieseling? It sounds exactly like that, only very briefly (just a couple of "whacks") - instantly upon startup - just when the engine actually fires up.

This is a very low mileage engine (10K miles). I installed a GM crate engine (and swapped out cam and heads) last summer. Nothing needs to be replaced. I just have some kind of tuning problem.

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'87 IROC 5.7l TPI - original owner!