Recapping the LS1 spring swap debate

[blackbombshell95]

well grinding i guess won't be a problem. i just want part numbers for EVERYTHING. I NEED to make a list. if you can help me out with that. thanks.

so to start... ls2 spring 12586484. are they SS?

[ikessky]

You don't have to do anything to the valve seals, they fit perfectly. When I say good luck for the seats, I mean no one is able to find a part number. However, I picked up a set that fit perfectly without grinding, I'll try to find the part number for those.

Or find out what application they are for.

[RacerX11]

ls2 spring 12586484. are they SS?

I don't think so. But why does it matter? They fit, and offer the spring rate and valve float resistance we are looking for....material shouldn't matter.

Marty

[blackbombshell95]

i thought material might matter if i use force induction?

[Froggx]

for your valves maybe, but not your springs

[geoffinbc]

Ok this is all good info here. But who has noticed any valve float with stock springs? Also has anyone see a power increase or anything wth going with LS6 springs? Stiffer springs are not always better. You do waste power if you have a stiffer spring and should only bother with the swap if you know the lighter ones will not do the job.

Just curious, not calling anyone out or anything.

[Froggx]

Well, I'm sure you know just changing the springs won't cause a power increase. My motivation for the swap is based on the fact that I'm building my engine to rev. I cannot speak for anyone else's reasons, however. From my understanding, the stock springs float at 6500 rpm. Without some serious porting work, cam modifications, boost that emphasizes top end power, or preferably a combination, there is no point in ditching the stockers, as normally our motors just won't breathe that high to make power up there. I don't know if anyone has yet revved high enough to experience float on the LS6 springs.

[geoffinbc]

Yea that was my thinking. Has anyone even stretched a pushrod engine enough to need LS6 springs.

[Froggx]

I really don't know. My target is 7000 rpm with a slightly lumpier regrind and 12-14 psi of push. My logic with going to LS6 springs was "better safe than sorry." I didn't think stock springs would take to that though, but I agree, LS6 springs are probably slightly too much. For the price, there is no better way to improve your valvetrain.

[Blackrider]

The LS1 shims sure as hell do not fit the guides on 2001+ heads, but all it needs is 5 min of grinding.


Like a glove!

[AaronGTR]

Just an fyi, the spring seats DO fit on 2000 3400 heads. They fit perfectly on mine. They changed the valve guide size starting with 2001 I think (maybe late 2000?). I think someone was looking for the part number for the LS1 shims too? It's #12565118. The LS1 springs are #12553696.

Froggx, so you said they changed the spring rates for the LS6 spring between '01 and '02, and that the '02 spring is the same spring used for the new LS2 engine right? I have the specs for the LS6 spring from '03. Do you know what the specs were for the '01 LS6 springs and if they were stiffer than LS1 springs?

If they are between the LS1 spring and the '02+ LS6 spring then they could be a good alternative for people that are just raising the rev limit and/or changing rockers but running stock cams. The LS1 has about the same open pressure as the stock LA1 spring, and just a little more closed seat pressure at our installed height, so they are better but something a little stiffer would be better at high rpm. I think the '02+ LS6 spring might be a little overkill if not running a cam, but like you said they are cheap and they would be effective. The '01 LS6 might be better though.

Just as a note, most cars with the 3400 are using auto trannies that won't shift beyond 6500 rpm anyway, so choosing a super stiff spring purely for high rpm is kinda pointless. I switched to LS1 springs just because my stock redline was 6000rpm and I had it re-programmed to 6300. With stock internals and cam (even with ported heads, manifolds, headers, etc) I figured there wasn't much point in going higher than that. Now that I have a cam on the way I'm switching to the '02+ LS6 springs. I don't think I'm gonna raise the redline any more though.

[3100 MPFI]

If you have a custom computer, and a hot cam, then the tranny can be made to shift higher.

Also, the LS1 springs bind up and the LS6 ones don't. When I bought my LS6 springs, they were the same price as the LS1 ones were.

With my LS6 springs, it allows my engine to see 7000 RPM (when the tranny shifts).

1993 ECM with custom programming, and a 1993 4T60-E

[Blackrider]

If you have a custom computer, and a hot cam, then the tranny can be made to shift higher.

Also, the LS1 springs bind up and the LS6 ones don't. When I bought my LS6 springs, they were the same price as the LS1 ones were.

With my LS6 springs, it allows my engine to see 7000 RPM (when the tranny shifts).

1993 ECM with custom programming, and a 1993 4T60-E

Programable PCM I have


But I dont expect the Shpings to let me spin it to 6500 the cam runs out of breath long before that.

[Froggx]

If I remember correctly the earlier LS6 springs were like 20 lbs lighter or something, I didn't even consider that for a swap, it didn't click in my head at the time and I'm sure not popping my springs back off now for something like that. I'm not sure if you can get a new set either but it I hear they can be found from time to time on ebay.

I'm running a 5-spd so I don't have to worry about my tranny holding my shift points down to low revs.

[AaronGTR]

If you have a custom computer, and a hot cam, then the tranny can be made to shift higher.

Also, the LS1 springs bind up and the LS6 ones don't. When I bought my LS6 springs, they were the same price as the LS1 ones were.

With my LS6 springs, it allows my engine to see 7000 RPM (when the tranny shifts).

1993 ECM with custom programming, and a 1993 4T60-E

Hmmm, well... I'm sure that you can program the computer to make the tranny shift higher, but it's more about what the trans will take without breaking. It could be a problem even with shifting pressure or fluid lockup at that high an rpm, dunno for sure. My factory manual and other specs I've seen though say the 4T45 max shift speed is 6500rpm. My stock rev limit was only 6000 and shift point was 5800 though, so I can't see a reason why they'd list the trans shift speed as higher and then not rev the engine that high (since it's capable), unless there's some problem with the trans shifting at that speed. I can only really guess though without testing it.

Regardless, I don't intend on revving that high since the engine internals are stock, and the trans is only partially built and I want to protect it. I don't think I'd see a big power increase from the extra revs anyway considering my engine mods. I just want the stiffer springs because of the cam I'm getting, not for high rpm needs.