Blown hemi compression

What is the highest blown alcohol hemi compression ratio anyone heard of? And piston to head and piston to valve in that case.
Bob Szabo
www.racecarbook.com

 

Back when everyone was running high compression, our TAD had 12.3 compression, the intake valve had .125 clearance to the pocket, the exhaust valve had about .150 clearance, and the piston to head clearance was .065 inches. This is about minimum clearance for everything, the pistons used to shine up the heads when we ran it hard. This was for a roots blower on a 463 cubic inch motor.

 

I have ran as high as 12.7 and know a few who went as high as 13.2
but the tune up window was very narrow
not uncommon to use sanding rolls to clean up the head where they were tapping
this was when we ran conventional blowers

 

I have noticed from reading that the more methanol you run you have a higher compression and if you ran nitro the more nitro you had you lower the compression , If you ran a nitro motor and added alcohol to the mix how would you work out what the needed compression is for whatever percentage of alcohol you run . I don't have an engine like that I am just wondering?

 

piston to head

on the Veney head engines they are run so the piston just touches the head at high rpm. when you take them a part you can actually see the mark on the piston and head.

 

Not a hemi but back in the day a friend traded a 8-71 blown chevy for a single plate nitrous motor out of the grave digger. They were up here monster truckin at the state fair and out in the wilderness. We put a mag 1471hh littlefield and a crank support on it. This was a concrete filled .190 over school bus block 4.25 crank 526 ci with aluminum water heads crane rocker arms 13.5+ compression, the old 114 dome pistons that you had to grind a notch for the spark plug or point the gaps down so they dont smash shut in 118cc chambers probably closer to 14:1 . In my 1990 pro stock ta it went 7.08 @ 194 on the third pass #43 boost. Next pass pulled the head studs out of the block, good thing you should have seen the wrist pins, had to press them out with a press. I put thicker pins in a rodeck that needed a line bore and caps ( that I had from the broke block ) that I got from another freind for $1500. It would go laps 6.90 197. Our track was not great back then and it would do 199mph @ 7800rpm hooked up or 194 @ 10000 doing a smokey burn out. I still cant hardly watch the tapes. I ran 199.97 -199.99 5 times in a row. Not a lie. Might have went 200 with a hi speed and did later with a different combo.The thing about a hi speed is if it doesnt improve the 330' your not getting it. I used to take it apart every week to check the hollow on the small end and the cracks in the pistons. We ran it that way till all the pistons were cracked except #8 figuring that if it cracked #8 it would break 1 or 2 this thing would not run with less than 40 degrees in it mag 3. After I changed the pistons to 11:1 and had to take fuel out of it. It didnt want more than 35 degrees.