Does anyone know what compression ratio I will get with the stock 1990 5.8L in my bronco with some GT-40 Iron heads? Anyone know how much I can safely mill them to raise the compression as much as possible?

Also anyone running a cam on the stock speed density system?

 

The combustion chambers for the E7 and GT40 heads are the same. Therefore no difference in comp ratio. You may need to drill out the head bolt holes on the GT40 heads, check first before doing this if the 351 bolts will fit thru the holes. As for your cam question, all engines have cams. Or if you're asking about larger than stock cams, Comp Cams has at least one that works with the SD system--XE254H.

 

So the heads on this 5.8 are the same as a 5.0 mustang stock... Interesting. Do you know the stock CR of this motor? Or how much I can mill the GT40's for compression? yes I know all motors have cams I was curious if there was some that were compatible w/ the SD system as I know with musatngs its rare to get them to run properly. Thanks for the info!

 

Some Gt40 heads cc out to 64cc. Check the volume before you start. The 302 is nominally 9:1 with a 61cc chamber. The 351 is suppossed to get the same because of a slight dish in the piston. Usually it's about 8 thousands per CC on most 302 heads. A .020 mill is standard, and that will usually drop them down to about 58cc from 61cc.