Thread: 512/514 CR for 91/93 pump gass

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Generally speaking, aluminum heads will allow up to 10.5:1 static compression ratio on pump gas, provided everything else is chosen to compliment the build for pump gas, like the camshaft intake closing point. For a street motor though, there would not be enough difference in power for me to choose 10.5:1. I would be very happy with 9.5:1 to 10.0:1 with aluminum heads because I could choose a shorter cam that would be more street-friendly. More SCR will require more cam, more torque converter, more rear gear, ad infinitum, until you have a combination that won't work well on the street anymore. Let's run the numbers with the 154167 piston.....

.7854 x 4.44 x 4.44 x 4.14 x 16.387 = 1050.4 cc's in the cylinder
combustion chamber = 75 cc's
piston deck height = 0 (stack of parts is 10.290", so cut block decks to 10.300" for use with a 0.041" head gasket to make a 0.051" squish)
piston crown = 28 cc's
head gasket = 11.2 cc's (I would use this head gasket for its pre-flattened steel fire rings that will be compatible with aluminum heads and will minimize brinelling).
http://www.summitracing.com/parts/fe...view/make/ford
Total cc's 1164.6
Subtract cylinder cc's from total cc's (1164.6 less 1050.4) and find 114.2 cc's.
Divide total cc's by 114.2 (1164.6 / 114.2) and find 10.2:1 static compression ratio with a 0.051" squish.

A retro-fit Howards hydraulic roller cam (part number 243745-10) and lifters (part number 91169) will close the intake valve at 40.5 degrees after bottom dead center and will produce a 8.7:1 dynamic compression ratio, just right for aluminum heads, pump gas and zero detonation with the tight squish. (well, tight for a big block).
http://www.summitracing.com/parts/hr...5-10/overview/
http://www.summitracing.com/parts/hrs-91169

Use a minimum 800 carb on an Edelbrock 7166 intake manifold. Use long-tube, tuned headers and cobble up an H or X pipe immediately after the collectors. Use a 14" x 4" air filter assembly so the motor can breathe. The cam will want a large dose of ignition timing. I would begin with 16 at the crank and 16 in the weights, then begin adding more at the crank, 2 degrees at a time, until power falls off. Experiment with vacuum advance to see what the motor wants. I would use a quality 10", 2500 stall torque converter. I always made it a rule to use quality parts in any location that was hard or difficult to get to for repairs, so I would also recommend that an SFI 29.1 flexplate be used, doesn't matter who the manufacturer is as long as it's tagged. Here's a converter I stumbled across.....
http://www.bmracing.com/products/404...5-crank-pilot/

If the motor kicks back against the starter due to the agressive ignition lead when firing it up, splice in a 15 amp (NC) push-button switch to the coil hot wire. Mount the push button switch on the left of the steering wheel to operate with your left hand. Push the button with your left hand to disable the coil and turn the key switch with your right hand. The motor will begin winding up with no strain on any parts. Release both switches at the same time and the motor will be idling.

OK, that's all the damage I can do.....

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