Any thoughts on the effect of filling in the head, on the reliability of the engine, i.e., when the head is filled-in as in the photos of some prior posts in the last few days? It seems that filling in the near side of the head (especially when it's filled-in down to the gasket, as one photo shows) would necessarily mean that the pressure on the piston top would not be evenly distributed, with most of the force on the off side, where the air-fuel mixture congregates, and much less on the near side of the piston, where the mixture has been squeezed out - at least until the piston is sufficiently down the barrel to sort of even out the pressure. It would put more of the force of the compression stroke on the off-side gudgeon pin bearing surface, uneven pressure (or pressure that's more uneven than stock) on the small end bearing, and apply a lateral turning moment to the piston as a whole, resulting in a reduced service life for the bearings and the piston. It may even put uneven pressure on the big end bearing. Am I imagining things?

email (option): jonny.rudge@verizon.net

Hi John..My 720 M20 has a modified head and is running just under 7-1 compression ratio as opposed to the M20s 4.9-1...I'm not sure how many miles it has done since I built the engine but it's over 30,000 for sure. and probably quite well over...There is no doubt that loadings have been increased and I don't drive it particularly gently, but there have been no reliability issues. I have had the barrel and head off to repaint it periodically and have 'tickled up' the valve seats a few times but haven't been inside the crankcase.
The M20 is so heavily built and in such a low state of tune it can easily accommodate these sort of alterations and remain well within it's 'margin of safety'...Ian

email (option): ian@wright52.plus.com

Real life "testing". Thank you, Ian.

email (option): jonny.rudge@verizon.net