I’m not having any luck finding someone for advice on what kind of gasket I need for my 3.4 engine with a 3.8 head. I placed the original steel gasket on the 3.8 head and it fits perfect. The block was decked to .007 and the head to .008. I was thinking of using a Cometic gasket but not sure which thickness to use. Anyone have advice?
Firstly measure the thickness of the Cyl head.
At the rear #1 measure from the top of the cyl head bolt [ where the D washer sits ] to the underside of head.
Non milled heads are 4.885 +/- .oo1
If your head measures 4.870 [.007 + .008 = .015 ] pick the gasket which equals that number or lower as you do not want to raise the head so much that you cannot get the cam gears mounted on the camshafts.
I would definitely keep it at least lower by .005.
Others on the forum with more gasket experience will probably chip in with more advice.
The 3.4/3.8 swap is of no consequence. You might CC the combustion chambers and mic the cylinder bore then find an online compression ratio calculator to see the affect various gasket thickness might have.
Thanks very much. The measurement you said to take is 4.86. So it appears the amount taken off the head was more than I was told.
regarding head thickness…is the measurement as described by Morris same for 3.4 as for 3.8 heads? Is this an accurate and true fact? is there another way to know if a given cyl head has been milled and how much…good stuff !! to know.
AND…next case–how to know if the block has been milled and how much.
Nick
Exactly what I was wondering. Going by what he says is the original measurement from the head stud hole to the deck is 4.885, MY measurement is 4.860, so a difference of .025. Does that mean I need a gasket which is .025 thick? I really didn’t think this would be the issue to cause the rebuild to come to a screeching halt But it has.