Hi chaps,
I know weve had posts touching on this previously but ive now got my head back from reconditioning/boring out to 70mm(was an A7 head) and ive just measured my volumes with an accurate burette. Ive got flat top 7.25:1 hepolites but as the A7 combustion chamber is i guess smaller i was hoping for the comp ratio to not go sky high, as im building the motor to a softish tune.
Ive just had a go at calculating and have come up with 8.05:1 which sounds fine but i would like you to check before i bolt the head on incase i need thicker head gasket or some other dodge to keep it low,if im wrong with my calcs.
Here are the clues:
-Standard bore A10
-head gasket 39 thou
-combustion chamber vol 42cc
-volume above rings/piston crown to top of barrel 2.3cc
I had head upside down and level and tried to avoid the fluid going covex by checking with a straight edge , same with above piston measurement.
I know it would be better to bolt head on to check as would be bit more accurate but i think this method should be close enough to check im in the right field.
You have 60 mins starting nooow,(you can use a slide rule and/or log tables)
no copying, and you will have to be accompanied if you need to use the toilet
cheers Spyke