Quote:
Originally Posted by mkpontiac
Regarding the 8 valve relief cast pistons. Those were installed in my car years ago by an engine shop that was using them to lower the compression ratio. My car originally had an advertised compression ratio of 10.5:1 and used the 066 cam which has an intake closing event at 26 degrees and it pinged when it got hot while using 91 octane. After installation of the cast pistons, which I was told lowered the compression ratio to 9.0:1 and a cam with an intake closing of 31 degrees my engine pings when it gets hot pretty much the same as it did with the original set up. I think the biggest contributor is that the factory piston was down in the hole 0.015 while the “stock replacement” 8 valve relief piston is down in the hole an additional 0.020 or 0.035. I am considering replacing the gasket with a 0.021 thick gasket available at summit. Will this help? I know it will raise the compression but I think the piston is way to low in the hole.
Mark
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Mark,
What temp are you running at when it pings? Water temp must be managed to stay below 180 preferable around 160. We have 93 Octane here , not sure the limits of 91 octane.
I don't think .020" gasket is a good idea.. What kind of inital/total timing are you running ?
Does it consume any oil thru the valve seals/guides? ]
Thanks