Originally Posted by JohnRR
Originally Posted by topside
I don't get the 9.0:1 Street Hemi idea - the chamber is not that sensitive to octane.
That's a fundamental reason Chrysler introduced it for the '51 models.
I ran 10.8:1 in mine with iron heads on Calif 91 and it never rattled.
Granted, the cam had some overlap that bled off a bit of CR, but it had a fairly aggressive curve, 36 total, + vac advance.


I don't get it either but then again the engineers at Chrysler thought it was a great idea to make the stage 6 wedge heads with a raised intake port entrance and stock iron wedge head valve lengths ... realcrazy


This may have had something to do with the length of the intake valves on the Street Hemi at least. In order to fit the Hemi into a production car Tom Hoover said they came up with the idea of canting the cylinder heads inwards to make the top of the Street Hemin more narrow. If you look at the SH combustion chamber it is not centered over the cylinder or the piston. Tom Hoover is explaining this with his hands in an interview and this made for the different valve lengths between the intake and exhaust valves on the Street Hemi. Don't know if that's why, just throwing it out there.

Mike

Tom Hoover lost interview 002PHSP 1.jpgTom Hoover lost interview centerlinehead to bore 1copy.jpg