Re: cylinder heads and compression ratios  
Re: cylinder heads and compression ratios -- david targhetta Post Reply Top of thread Maverick Message Board
Posted by: 74merc
01/18/2002, 00:26:05

 the 73 to 76 have dished pistons and taller blocks, the 77-85ish had 69cc heads to lower compression, you should have 8.4:1 compression, best way to raise it is to swap heads, the 77s flow like crap and have huge combustion chambers, not even worth fooling with.
76 and below would be good heads to bolt on, or 87 and later.
bolt on 50-70lbs torque, probably 50hp.
you should have a good block and flattop pistons, if you get old heads, you'll have a pre smog type engine.


My engine has a compression ratio of 8.1:1 (its a '77) and i feel that it is too low to get good performance, but I am not sure. DOes anyone have an opion that would help me figure out whether or not this is low. Also, what size of combustion chambers are you guys putting in your 6 to 8 swaps. The shop manuel i have says mine are between 67-70cc is this correct? If I mill the heads is it possible to raise my compression to about 8.5:1 to 9.0:1 ?


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