compression question

[Roger G.]

assuming a stock rebuild, with 30 overbore, does the piston dome need to decrease to maintain the stock CR?

[Joe L.]

Re: compression question

assuming a stock rebuild, with 30 overbore, does the piston dome need to decrease to maintain the stock CR?

Roger-----


Everything but the bore size being the same as stock, yes. However, keep in mind that depending on the piston, it may not be possible or advisable to remove enough material to compensate for the compression increase due to the increased bore size.

[Dick W.]

Re: compression question

Also be advised that the advertised compression ratio was somewhat optimistic at times. Higher numbers made better marketing. Unless your heads have been cut, I doubt that .030 overbore would get you past advertised compression ratio. The only real accurate way is to CC the heads and block.

[Roger G.]

Re: compression question

Thanks Joe and Dick

[Joe R.]

Re: compression question

Roger,

As a somewhat new member, you may not have seen the compression ratio article that was in the Restorer a while back. It is reprinted in the following newsletter, starting on page 5:

http://stlouisncrs.org/news_files/St_LouisNCRS_ChapterNewsletter2ndQuarter2012.pdf

Joe

[William C.]

Re: compression question

Remember that a .030 overbore is relatively miniscule, and factors such as have the rods been rebuilt (will shorten the rods) is the head gasket thicker than OEM (many high-quality versions are) Have the valves been ground (drops the valves and /or seat and increases chamber volume) generally make a .030 overbore a "no pain" issue from a C/R standpoint.