leaded or unleaded fuel

33IMP said

Yes, but what if the piston manufacturer says it has a certain dome volumn? Do you not believe them?
I absolutelyagree that lots of times people don't have the cr they think they do, because they simply don't measure. I have a trw "11 1/2 to 1" engine that is really in the low 10s, determined by actual deck height and chamber size measurements . I have another with arias "12 1/2" pistons that are more than .050 in the hole ( damned if I'm gonna deck a real max block .050 !), and with an 84cc max head is barely 11 to 1.

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I believe no one. In 1994 I took on another engine builders engine because his stuff was slow.

It was a 9:1 class and it was enforced. We were reusing the pistons and I had all the paper work for the pistons and everything else.

I no longer remember the exact number of the dish, but what the paperwork said and what they were was not the same. Not by 7cc’s. They were 7cc’s too SMALL.

So when the owner went from a back marker to running up front, he got checks and FAILED. And that was on ME.

The vast majority of dome/dish volumes are not what is claimed. If you have a compression rule, you damn well better know because if you don’t, you’ll get burned.


Never trust anything. Measure everything. Then you KNOW.