Ken,
Everything I can find says 1976 was the only 1500 with 9:1 compression in
the US. The rest had 7.5:1. UK had 9:1 in all 1500's.
You could just change the pistons to 76 pistons, no milling required.
The GT6 competition prep manual describes a somewhat indepth method of
milling the head. I says (this is paraphrased): With the head off, use a
depth mic to measure the distance from the top of piston 1 to the head's
deck height at its TDC. Repeat measuring for the other 3 pistons. The
largest measurement (the shortest piston) is the amount milled from the
block to make a zero deck clearance for the shortest piston. Now measure
the heights that the other pistons rise above the deck and remove that
amount from the top of each piston bringing them to zero deck clearance.
Now all pistons' heights at their TDC will equal and have the same zero
deck clearance. The book says this method helps reduce the differences in
length of the connecting rods as well as raise compression. When the head
gasket is installed and torqued, the .038 distance is just enough to allow
for the connecting rods to "stretch" during high rev's.
Granted this info is from the GT6 competition prep manual but I don't see
why the same procedure would not work on a 1500. The person doing the
machine work would probably tell you if this is proper procedure, and the
proper measurements.
John Goethert
Knoxville, Tennessee
john@triumphspitfire.com
http://www.triumphspitfire.com
76 Spitfire, 71 GT6, 75 Spit parts car, 90 Miata
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