Compression ratio for 95 octane pump gas

Z

zilog

Guest
I warped the head for my MA12 engine a couple of days ago, and I will now take some off using a mill. How much in millimeters can I take off without predetonation or bent valves? What I am interested in is how high can I go with the compression ratio and still be able to use torque at low revs without detonation. Second, this compression ratio, is this the relationship between the minimum amount of oil I can fit inside one of the combustion chambers with the piston in top and (1235/4 cc), or is it measured as the maximum cylinder pressure measured using a pressure gauge?

I would also like to have a go at the inlet and outlet canals, aswell as the inlet manifold. What is best to do here given a couple of hours and a dremel?
 

stonesie

Grease Monkey!
For the head skim i would take as little as possible off to get it flat again.

And for a DIY job on the inlet and exhaust ports i would match them to the gaskets and smooth them out removing any rough or sharp edges, but leave the inlets slightly rough (not mirror smooth) as this helps to keep the atomised fuel from sticking to the walls of the ports.
 
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Z

zilog

Guest
For the head skim i would take as little as possible off to get it flat again.

And for a DIY job on the inlet and exhaust ports i would match them to the gaskets and smooth them out removing any rough or sharp edges, but leave the inlets slightly rough (not mirror smooth) as this helps to keep the atomised fuel from sticking to the walls of the ports.

What is the reason for taking off as little as possible, is it already at a high compression ratio?
 

Andrew

Club Member
You won't be able to raise compression ratio that much with a skim - so it's better that you just take as little off as possible. You'll find it hard doing it with a mill to the required surface though.
 
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