Compression Ratio, Will I be able to tell the difference? Options

[sdoolin]

Rebuilding(ish) my 2056. On my first build I was able to achieve a compression ratio of very nearly 9.0:1. With this build, I am having to add .020 spacers below the jugs to get any measurable deck height in the jugs. I am calculating a compression ratio of 8.6:1.

Will I notice the loss in compression ratio?

[Superhawk996]

0.100” clearance to the exhaust valve is starting to push what I’d call reasonable for an aircooled street engine. There are water pumper race engines running less. The fact that you said “more than” rather than an exact number concerns me.

The clearance to intake isn’t as critical. The intake valve chases the piston on the intake stroke. The piston chases the exhaust valve on the exhaust stroke.

However, remember that air cooled engines run hot vs water-pumpers so growth of the exhaust valve, piston expansion, and rod stretch at high RPM and valve float at high RPM can be a thing.

I’d be checking that clay clearance on all 4 cylinders and making sure I’m making that measurement accurately and not just relying on 1 cylinder to represent all 4.

I’m also going to suggest that you should be talking with Len and following his advice for valve to piston clearances if you’re trying to build an engine that is trying to absolutely maximize HP by building to the edges of limits of safety that were built into stock components. Don’t rely exclusively on some internet dope like me. (IMG:style_emoticons/default/laugh.gif)