:driver: Hey, that all sounds about right for everything, with the exception of the 91 octance fue:confused0006:l!!!--- IMPO 93 would be the bare minimun with the 11.5 to 1 and 36 degrees!!--This wouldn't even be possible without the Aluminum heads to help dampen the detonation, and the 264 274 @.050 cam, and a real good cooling system!!---milton--- PS-- I like the cam choice!!:tu
In mine we dropped calculated compression to just under 11:1, used Dart aluminum heads, having seen the destruction from failed/brindled rollers from solid rollers went with hyd. roller cam. I am sure my HP and ft./lbs. are less than yours, I was upgrade copying a magazine build from back when Dart was launching their SHP blocks/shortblocks. Use 93 octane, 3.50:1 rear gear, 36 degrees total timing, mechanical only advance I consider mine a good weather daily driver, it does love fuel but it is so o o much fun to drive. Point is compression and timing listed in this example can work with right tune and cam timing.
This is also a very similar build to mine, except mine is a measured 11:1, with a solid roller by Bullet, @.050 254/264 .625 lift....no prob on 93 pump. 26* initial and 36* total. AFR 220 CNC ported...pulls like crazy, even down low.
My guess is that narrow lobe separation (106 degrees) will let you get away w/ that much compression on pump gas. I doubt the heads have anything to do w/ it. Especially w/ today's gas the higher the compression the shorter the fuse.
You guys need to re-read my post. Of course heads have a huge influence on power. The issue at hand was: will an 11.5:1 engine survive w/ 91 octane gas?
The tightness of the lobe centers will mean the intake valve will stay open a few degrees after the completion of the intake stroke......this will reduce some of the cylinder pressure thus "forgiving" the low octane. I don't think the AFR heads themselves are going to prevent detonation.....squeeze is squeeze.
Detonation is base on cylinder pressure, but the piston/chamber design has a huge amount to do with it.
Steel heads, older factory chamber designs, dome pistons and too much quench are a recipe for detonation.
My understanding is that max quench will actually help avoid detonation...I built mine with a "0" deck and a .039 gasket to accomplish what most would consider max quench, or least acceptable piston to head clearance. I know some builders run them even tighter, but that was as tight as I wanted to go. No detonation, even loaded up in 6th gear with a T-56 with a .5 overdrive... I did have to tune the advance curve since I run 26* initial I did not want that extra 10* coming in too soon, like where I would be cruising in 5th or 6th at around 2200 rpm or less, here is the curve I run:
FBO 10* Advance bushing, 26* initial – 36* total
2 heavy silver springs …27*@2000…30*@2400…32*@2600…36*@3100
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