The new high eutectic (spell ?) low expansion pistons require a HUGE end
gap on the top piston ring. a 4 inch piston in a 289 requires almost
.040 gap because the piston reflects so much more heat down into the top
ring that the expansion is huge. We used to gap those rings at more
than half that figure with forged pistons.
I am building an extra engine for my GT 40 right now and I was
astonished at the gap I had to run in Keith Black pistons, but just on
the top ring.
Larry Dent
PS. To add one more comment on the question about horse power in the
old twin cams. I ran an HRE (Gus Hutchenson out of Texas) 1300 cc twin
cam in my Lotus 23 back in 1969 to 72. That engine was very exotic with
titanium valves and other pieces made of un-obtanium and it made 155HP
at 11,500 RPM. We were all sworn to silence on that high RPM as Gus did
not want anyone knowing what he did or how he did it. I once missed a
shift and put the tell tale to around 12,500 and when I called Gus he
said "don't worry, the engine is safe to 13,000 on a momentary basis".
That was in 1969 folks.
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