closed chamber heads on OC pistons

[Jeff M.]

MY 71LS5 has open chamber 71LS6 pistons in it. My question is can i install 70 closed chamber LS6 heads on my motor without running into piston clearence problems. In other words is it a bolt on and go situation by putting on any closed chamber heads on open chamber pistons

[Bill Clupper]

Re: closed chamber heads on OC pistons

My understanding back when the Open Chambers were introduced was that you cnnnot use the OC pistons with a closed chamber head. They will hit the head. you cna do the reverse, and use open chamber heads on closed chanber pistons, although some loss of compression will result.

[Wayne M.]

Re: closed chamber heads on OC pistons

Jeff --- What do you mean by CLOSED chamber '70 LS6 heads ? If you're referring to #3946074, this is an OPEN chamber design with a combustion chamber volume of 118 cc, so by default are OK with '71 LS6 pistons. Are you running a stock LS5 or LS6 cam ? Any other combo, I'd check the valve/piston clearance with clay putty.

[Jeff M.]

Re: wayne 70LS6 #3964291

the 70 LS6 head #3964291 was a closed chamber head of 108cc used in the chevelle LS6. I would like to use a set of 71 LS6 heads if i can find them. The 70 heads were offered on ebay, and i wanted to make sure they would work before buying them

[Wayne M.]

Re: wayne 70LS6 #3964291

Jeff --- I'm no engine builder, and Bill's no doubt correct in his assessment. "How to Hot-rod BB Chev's" has this to say: "There is no way to open up closed-chamber heads to accommodate open-chamber pistons" The interference is in the plug side.

[George Daina]

Can't do what ya wanna do.....

besides, you're taking a big step backwards with the closed chamber heads. The Closed Chamber heads are known as smog heads due to the poor design of the combustion chamber. When the cast iron heads hit the counter way back when in the mid 70's, guys dumped the smog heads for the open chamber heads and picked up 30-35 horses, even with the drop in compression. Don't bother with those heads, they're junk compared to the open chamber.

[Joe L.]

Re: wayne 70LS6 #3964291

Jeff-----


I can confirm what other responders have said; you CANNOT, under any circumstances, use open chamber pistons with closed chamber heads. These pistons cannot be milled or otherwise modified to work, either. As Bill Clupper mentioned, you can use closed chamber pistons with open chamber heads, but compression ratio will be significantly reduced.