58cc or 64cc head?

[PKRWUD]

Depends on how good you are at communicating with JE.


The '87 - '93 5.0 HO was advertised as having 9.1:1 compression.

B.S.

It works something like this:

Typical E7TE heads have an honest 64cc combustion chamber.

The area above the rings, but below the deck, at TDC, plus the area from the 4 valve notches in the piston, total 5.5cc.

Average thickness of a crushed head gasket is .047". That equals 9.68cc.

Add those three up, and you get 79.19cc.

Add to that the swept volume of the cylinder (617.78cc), and you get 696.97cc total cylinder/combustion chamber volume.

Divide that by everything BUT the swept volume (79.19);
696.97/79.19 = 8.8

Therefore the compression ratio is really 8.8:1

To increase the compression back up again, you could straight cut the head.

Cutting .010" would reduce the combustion chamber size to 62.4cc, and would increase the compression to 8.96:1.

Cutting .020" would reduce it to 60.92cc, and increase compression to 9.12:1.

Cutting .025" would reduce it to 60.15cc, and increase compression to 9.2:1.

Cutting .030" would reduce it to 59.38cc, and increase comp. to 9.3:1.

Cutting .035" ------------------------58.61cc, ----------------------------9.37:1.

Cutting .040" ------------------------57.84cc, ----------------------------9.46:1.

Does that help?

Take care,
-Chris