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Compression Ratio - Maximum Allowable

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What is the NASA limit, VVT?

Frank you will get a tear down so pull in with 1 to go!
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K. Webb
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Mike Babcock

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You hava a mishmash of stuff there. The one marked STD probably isn't even a Mazda part. The late “factory” crate engines that came out of Canada were assembled by someone else and used some conspicuously different parts, but I’ve never seen that stamp in an original or crate engine. One possible explanation is that it is common for aftermarket pistons to have a larger dish, or higher pin height, intended to drop compression by .5 or more. The rationale is that old engines being rebuilt often also have the head and/or block decked which raises compression, are otherwise tired and often get fed cheap fuel. Lowering compression a bit reduced the risk of harmful knock. That’s what I suspect you have run into.


Probably the case... but it still doesn't explain the variance in the spare block.  Again, that one appears to have 4 like pistons.


I'm just wondering if enough data has been gathered on this measure across other 1.6 engines to support whether or not this level of variance is normal or not.  I only have the two, so...  

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