Two more questions about 3500 heads

[ForcedFirebird]

1. What is the max lift with the LS6 spring conversion?

2. Has anybody used 3.4 pistons with 3500 heads? If so, what kind of valve clearance do we have?

I will check at final assy, but if someone knows...

[Superdave]

when i had my machine shop checkmy old LS6 Yellows, he said coil bind was at .560 lift so roughly .500-.510 was safe. I know others are running a ton more lift on 3400 heads but there may be other variables involved there.

I was using .015" thick SBC shims and stock 3500 retainers and locks, around 1.7 installed height.


That's something that you should take in to your local shop and have them check out.


i don't think 3.4 pistons with 3500 heads has been done but valve clearance shouldnt be a problem since the valves aren't open when the piston is all the way up.. running a taller or longer duration cam might be a little risky though. Maybe toss on the heads with some clay on the pistons and find out.

[ForcedFirebird]

when i had my machine shop checkmy old LS6 Yellows, he said coil bind was at .560 lift so roughly .500-.510 was safe. I know others are running a ton more lift on 3400 heads but there may be other variables involved there.

I was using .015" thick SBC shims and stock 3500 retainers and locks, around 1.7 installed height.


That's something that you should take in to your local shop and have them check out.


i don't think 3.4 pistons with 3500 heads has been done but valve clearance shouldnt be a problem since the valves aren't open when the piston is all the way up.. running a taller or longer duration cam might be a little risky though. Maybe toss on the heads with some clay on the pistons and find out.

I work in a machine shop, but we don't specialize in heads, so I will bring them in.. I am buying the spring set-up used, but will use new valve seals when I get them, they are still attached to some '02 3400 heads.

Clay is the way I was going to check at final assy .

Thanks for the heads up, my plan is to use either a 260 or 270 cam, but with the 1.7 rockers also involved it seems like I'm doing a lot of things that haven't done before.

Don't know if you saw in my other thread, but I was able to polish the entire LIM.

[SappySE107]

1331 grind with 3.4 DOHC pistons and 3500 heads had a lot of room (over .200").

.539 has been ran on stock heads with LS6 springs. Its safer to give them more room, which is why I prefer the comp springs.

[Rhedalert]

3.4 pistons and 3500 heads is something I was thinking about. One of us has to get on that

[Superdave]

1331 grind with 3.4 DOHC pistons and 3500 heads had a lot of room (over .200").

.539 has been ran on stock heads with LS6 springs. Its safer to give them more room, which is why I prefer the comp springs.

Moon's running .559 with the LS6's on 3400 heads..


but yah, the comp springs are the safe way to go. the 26915's that i have are very nice

[ForcedFirebird]

I know the Comp spring is a better choice, but cost is a factor at the moment. And now that I'm using a 3x00 top end, spring replacement just became MUCH easier (along with valve adjustment ).

Ben, was the DOHC pistons you checked the clearance from the valve relief, or top of piston?

[SappySE107]

From the top of the piston (domed). This was with it timed. If the chain breaks, its fucked.

[ForcedFirebird]

I measured today.

With stock 3500 heads, LS1 shims/seats (.030" IIRC), stock locks/retainers, and LS6 yellow springs was exactly .5613" at coil bind.