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So closed chamber with piston in the hole approximately .020". Using a .020" gasket ( how thick are the thinnest shim availible ?) would give .040" quench. Iron or aluminum head? I've had small blocks have less detonation with quench at 12-1 than w/o at 10.5-1. Would it work in this case? it would only cost the gasket set.
Doug

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Doug he has numerous threads on this over the past year or so, I didn't keep a scorecard . Pretty sure the original combo had the .020 piston depth and .021 shim gasket with .509 MP cam and it pinged , it has spiraled out of control since ...

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Maybe he should look for other issues:
Timing not accurate,bad marks,box, dist and etc.
Too hot of plug.
poor fuel or lean condition
Cylinder head temperture
Oil detonating in cylinder..
If some of the information mentioned is correct with his clearences correct timing should cure the issue provided he doesn't have other issues.

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This subject has been beaten to death on the Q&A page.

R.

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yes, but he's looking for answers and now has moved it from a more general thread to a more specific one.

he has done many, many things to try and take care of this problem, and it's still haunting him, so he's just trying to get as much info as possible before making the next decision.

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He been given a number of ideas on what to do, there are only so many choices and most/all require disassembly and spending money. He seems to looking for the EASY fix and the failed attempts haven't fixed it , nor were they FREE ...

He needs perfect quench to even get it to work , he won't deck the block and putting thicker head gasket in did lower the compression, but it didn't help.

Ok lets try a cam change , bigger off the shelf cam and no quench ... didn't work , maybe a CUSTOM cam might have worked ??

Have the heads CNC'd to make the chambers bigger , but can they get big enough to lower the compression so he can go back to the thin gasket for quench ... hasn't tried this yet ...

Next is mill the pistons , which mean disassemble and REBALNCE ... $$$$$$

If he is going to do the piston mill he should just call a Diamond WD and get a new piston that is at zero deck and has a D dish big enough to lower the compression ... then he can go back to his .509 cam ...

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Any question no matter how many times it has been asked deserves an answer,ask enough people enough times you just may get lucky and find a solution.I would start a process of taking the different suggestions and through the process of elimination search for an answer.Start with anything easy and cheap that can be timing related before going the tear down big dollar route.

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Most logical steps !
If it hasn't been done before........

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When I built my 493 Ross didn't make a shelf stocking piston with a big enough reverse dome to keep my CR under 9:1. I asked about just taking the one they had and milling it to the desired size and was told it would seriously weaken the structure of the piston.

Given how light most forgings are now it stands to reason that they are engineered for max strength with minimum material already. I paid the extra charge for a custom piston.

Kevin

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