@35mike 

Nope, didn't forget.

Which is why I said boring oversize in and of itself would have no effect on the compression ratio.  🙂

The combustion chamber is just the cylindrical shape in the block above the piston at TDC.

The next year however was a different story.

A large over bore in a '29 WILL raise the ratio a little, but still not much.  🙂

it looks like the links in the 'schools in session' thread are no longer supported

To get the full info out of the "School is in Session" discussion, I suggest downloading the PDF, which is located in the following, club member only resources area of the main web page (vcca.org).

1. Go to the Resources pulldown menu,
2. Click on FORMS - Downloadable,
3. Then click on Technical-Vehicle-Resources,
4. Then click on  1912-1928.

Look down the list of documents and Ray Holland's document is labeled 1928_Engine_Rebuild_Class. You can read it online or download it.

I printed it out to use during my engine rebuild and it was invaluable! I put post-its on important pages, which helped a lot!

Cheers, Dean

@david-siedschlag As you probably know the Chevrolet fiber timing gears are no longer being reproduced. So pulling one off and probably destroying it in the process is not too inviting. The cam grinding company I use does not require the gear to be taken off. Their grinding machine has plenty of space to clear the gear. The last one I had them do for me they asked if I wanted a little more lift. Between the extra cam lift and the 1-1/2 to one rocker advantage it gave me an extra 1/16". That may not sound like much to someone working on a racing cam, but in this application it amounts to a 25% increase. In my mind this is one weak area on these old engines. They work well at idle but anything above that it is starving for air.