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1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-04-2014, 04:56 PM   #11
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I haven't spoken with Cometic yet, so they are still a possibility. There is an outfit online called "Gaskets to Go" that will make MLS gaskets in your specified thickness based on either a pattern or an old gasket. I looked into them a bit and find they are in Thailand. Much prefer to deal with a U.*. based company.

I think I understand the basic concept on the knock issues and I certainly agree for best power in a boosted application, low c.r. provides more room for the charge. The tight squish/quench theory is to better force the mixture out of the perimeter towards the center and momentarily remove the fuel that can ignite from the high temperature and pressure of the main charge. In this case, I was probably my own worst enemy. The taller pistons increased c/r and was intended for N/A use. Later on I decided to put together a turbo system, which actually spooled better than I had hoped. While I tried to limit boost to 7-8psi, it would reach that level from a dead idle to full boost in only one frame of the scan tool recording. In any case, from other forum discussions, it appears I had inadvertently created squish in a sort of danger zone for my application. The original .100-.105 clearance distance would have been fine, and tighter, like I want to do, MAY be okay also, but the .050"-.060" I have now creates a space that is more prone to knock in a boosted application. If I had gone down .5 c/r instead of up by that amount, everything may have been happy. It'* part of the price paid for experimenting. Mistakes can be made. I have also toyed with going very high compression, maybe 12:1 using a Ford 3.8 piston, and using E85 only. Probably another of my bad ideas
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Old 04-05-2014, 09:09 AM   #12
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dont know much about e85 ecept most times i takes fuel upgrades because of how much it takes to get the proper mix. big lines/pump/ injectors. as you said all the mods you did would be good for a n/a engine, not so much for a turbo. with gas they usually shoot in the mid 8'*. and taking away cylinder volume from the head area takes away room for fuel air, as does taller piston which is opposite of what you want for a turbo
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