Thread: Piston and valve clearance

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How much lift can I put into a LS6 motor. Compression has been lowered to 10.2:1. Running a spd with 26" tall tires. I would like to run a solid roller.

Originally Posted by Darrin Hammond

How much lift can I put into a LS6 motor. Compression has been lowered to 10.2:1. Running a spd with 26" tall tires. I would like to run a solid roller.

I don't think anyone can answer your question as asked, there are too many variables that we don't know. Assemble a head with checking springs on each end of the head and use a dial indicator on the retainer as you push down on the valve stem tip to find the points of interference (usually at overlap between the piston crown and the exhaust valve). Don't push on the retainer, you will unload the locks and disassemble the whole mess.

You want checking springs on each end of the head so you can determine if the block is skewed from front to back. (block decks not parallel with the main bearing bore). Snug a couple of head bolts down by hand, without head gasket. Then, you can add head gasket thickness to your clearance values.

Also, no big deal, but you have posted this thread in the BBC forum. The current/recent production LS-6 is a small block.

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tech-I think he's referring to BBC LS6 from back in the 70s----check his prior posts--all about 70s ls6




if he is talking about newer LS6, I'll be able to post what NICkEY is doing with the new Camaros later today

i would think the cam maker could answer this better than any of us .. i have`nt worked on an LS6 before .. never mind my post .. me and jerry at the same time ... hA !!!

just did a custom cam that was ls6 around 560 lift and 230@0.50 ground on a 110 and used the ls3 heads with 1.8 rocker comp rocker arm kit with comp lifter /spring kit #54200 was a LS6 stock bottom end and did fit runs very good in a 4 wheel drive hill climber /mud hole deal . i know the ls1 with a 1.72 rocker with the Trex.s cam will not fit in the a ls1 engine with stock piston with out work been there done that .but that engine i put comp solid roller on that Trexs cam and just tight lash it to .016 that was in a road coarse car it did get the hell beat out of it . the GM race hyd roller lifter can take alot of rpm if you set it up right would not be so fast in moving out of the hyd lifter cam go with sort valve lifter much the same as a solid... OH OK IF your taking about a BBC LS6 engine i do know about how much cam you can put in one with no piston work . i done many but what piston ? LS 6 piston gm or speed pro trw ? what heads do you have on it ? if the heads have not been cut much then i can get you close but GM never made a 10to1 ls6 so what do you have ?

I am talking about a BBC ls6. It does have the OEM pistons in it (pn 3963550) I put the 188 heads on it to lower the comp. Nothing has been done to them.

ok i see were they show the 9to1 in ls6 gm power book ? ls5 was the lower cr engine past 1970 gm went open chamber i did know that but the older close chamber were around 11to1 you must have a trw speed number piston like the l2349 would be 9.99 cr with a 119 open head would have a .265 dome 5/64 top and 2 ring if that is the piston you do have there is not much room for big cam. were the valves set in the heads play in to this as going to a bigger valve many time.s is above the head deck . i used this piston . but i used cams like this in engine with them pistons with some room Crower street roller like 242/250 @.050/581/573lsa112 Erson r286-1 @.050.245/254 .629/.629 lsa108 and schneider 246/264./604/610 blower cam in a stock ls6 so abit less on the ex side like 250to256 on a lsa of 112 cams used . see the pattern here nothing bigger then 250 on intake side and a Lsa of 110 to 112 should help on over lap. but nothing is a guaranteed that Erson should fit if stock valves not over deck block or heads it all stacks up and adds les to PV room ISKY has v.o.t.c valve opening at top dead center so you can work it out but i had new gm heads were off . if you get close to PV you must check every hole as thats not a machined fly cut valve relief in them pistons but forged net shape . with the low CR you have you do not want a cam much bigger then 240 @ 050 any ways i woud need much more input and a good cam pick