Compression Ratio Answers??
> Ok I am going to rebuild a early 72 head and
> put it on my late 240 73 Motor, and I
> beleive it was Jeff who said that the late
> 73 240 engine had slightly domed Pistons,
> can anyone confirm this??
NEVER HEARD OF STOCK DOMED 240Z (83mm) PISTONS. THEY WERE ALL FLAT TOPS FROM WHAT I UNDERSTAND.
Jeff also stated
> that the early e-88 on a late 73 motor would
> raise the compression to about 9.5:1 is that
> correct?
GET SOME FACTS FIRST. ASK WHAT COMBUSTION CHAMBER CC HE IS USING TO CALCULATE HIS CR. A STOCK E88 HEAD IS 44.7cc. THE 'EARLY' HEADS ARE SUPPOSED TO BE SLIGHTLY DIFFERENT COMBUSTION CHAMBER SHAPE, ALTHOUGH I DOUBT THE CC'S ARE THAT DIFFERENT. MAYBE UP TO 1-2cc DIFFERENCE.
JUST FOR GRINS, CR IS CALCULATED WITH THE FOLLOWING FORMULA:
CYL. VOLUME = PI/4 X BORE2 (CM) X STROKE (CM)
FOR A 2.8L = .7853982 X 8.6 SQUARED X 7.9 = 458.9cc
CHAMBER VOLUME = HEAD CC + GASKET CC + DISH CC(- DOME CC)
COMPRESSION RATIO = CYL. VOLUME + CHAMB VOL./CYL. VOLUME
If that is correct what kind of HP
> gain will that give me from my 8.8 or 8.9
> compression ratio.
I WOULD GUESS MAYBE 5-10HP AT MOST. THIS DEPENDS ON YOUR PARTICULAR SETUP, AS THERE IS NO DIRECT WAY TO MEASURE C.R. TO HP.
Is their anything I can
> do to raise the compression in my car with
> out spending spending too much or using the
> parts I have already??
YOU CAN SHAVE THE HEAD, OR INSTALL A HEAD WITH SMALLER COMBUSTION CHAMBER TO BEGIN WITH. ALSO THE 1mm HKS HEAD GASKET IS SLIGHTLY THINNER THAN THE STOCK (1.25mm) GASKET.
> Dustin Morris