1971 LS6 pistons

[Warren F.]

Several automotive magazine articles written about the '71 LS6 engines mention the pistons used were the "70 high dome units". I take this to mean the 1970 LS6 piston. It's kidney shape dome notch used with the closed chamber iron heads to achieve a 11:25 to 1 compression with the 106 cc head, I would think would work with the open chamber ZL1 118 cc head, along with a thicker head gasket would reveal a 9 to 1 compression. Does anyone know this to be true?

[Clem Z.]

Re: 1971 LS6 pistons

1970 454 CI 450 HP engines 11.25:1 CR used .303 high 31.6 cc domes with 106.9 cc head chambers. 1971 454 CI 425 HP engines 10.1:1 CR used .095 domes with 103.1 cc head chambers. these are NHRA specs supplied by GM

[Clem Z.]

addendum

the 1971 pistons have a 13.10 cc domes

[Clem Z.]

calulating CR

go to www.bgsoflex.com/auto.html

[Chas Kingston]

[Clem Z.]

[Chas Kingston]

[Karl #35089]

Re: calulating CR

Hi Clem: Thanks for the link. I see how to calculate CR. Is it also possible to physically measure actual CR on a given engine? How is that done? Thanks, Karl

[Clem Z.]

Re: calulating CR

there is a machine called "katech whistler" made by katech engines. it works the same way different levels of water in a pop bottle give off different sounds when you blow across the top. it is a frequency counter,air is blown into the cylinder with the piston at exactly TDC and as it comes back out the machines computer reads the frequency and calculates the CR. you have to put into the computer the volume of the cylinder which is gotten by using a P&G cubic inch checker. the CR machine was invented at GM to test the engines at the assy plant to make sure the stack up of tolerances did not make the CR too high. try google with "katech whistler" and you may come up with a better discription how it works but mine is very close as i used them at the race tracks

[Joe L.]