mchicia1

Will the ls6 springs be able to control the valves with the ls6 cam inside an ls1 with the stock ls1 heavy valves? I already have the yellow springs on my car and I have no problem swapping a cam in just a few hours, so I wanted to do a budget friendly upgrade to the ls6 cam (I have ported heads already) and shoot for 400+ rwhp. It would only be a $250 swap since I have the springs on the heads already. But now I am starting to think this may not work because I have the stock, heavier valves. Thoughts? I could always put on the $250 psi springs, which work with the stock hardware, but then it would be pointless to swap to the ls6 cam as I'd only be $150 more from a custom cam.

baxsom

i asked this same question a week ago and was told dont waste my time and to quit being cheap. you could however go to the PAC 1218 springs for about a lot cheaper than 250 bucks.

mchicia1

Ya, actually AI just told me this is the reason GM went with the lighter valves in the z06...

So these springs will have issues controlling the valves at high rpms.

How much are the pac 1218s? Do you use stock hardware with those?

I am so up in the air about my cam, it is not even funny...

3 weeks ago, I was sure I was going with a custom AI grind ( they do great work). But my original goal of the car was reliability/longevity over power. I really enjoy just driving the car with 370 rwhp...it pulls great and idles/drives exactly like it did with 300 rwhp. I know for a fact with an ls6 cam, I will retain those manners.

So then my mind swayed to the ls6 cam...now that I realize I can't run the stock yellow springs (with good reliability/longevity) I would feel dumb spending money on springs and going with just an ls6 cam. So now I am thinking about a custom grind again LOL. So tired of changing my mind.

baxsom

the pac 1218s can be had for around 150.00 and uses all the stock hardware. if you already have a LS6 cam then keep it. I have the 02 LS6 cam and 01 heads and will be more than happy with the gains they provide.

mchicia1

I do not have the ls6 cam yet...

Right now, I have headers, ls6 intake, and AI ported 799 heads. Car made 370 (about 70 HP increase). But I also have the smallest ls1 cam possibly, which is like a 199/199 and less than .480 lift. So I know I would pick up a pretty good amount of HP just from the ls6 cam and would most likely get 400 rwhp.

AI said they have two grinds that work with stock yellow springs...gonna get some more info about those.

bearcatt

Guys there is nothing wrong with the LS6 yellow springs.

They are fine as long as you don't install them on a cam larger then what is used on a 2002 + C5 Z06.

They yellow springs will also work just fine for an LS1 engine with the non-sodium filled valves. They are superior to the regular LS1 springs.

I can't see spending for PAC 1218 springs. I was going to spring ( no pun intended ) for the so called mighty PAC 1518 springs, until I started reading threads about them breaking recently.

vettenuts

I don't think the yellow springs will control the heavier LS1 valves to the RPM capability of the 02-04 LS6 cam. If you go this route I would use PAC 1218's or PSI 1511ML's. The PSI's may require some shims to increase the seat value but you would need to determine the installed height to figure this out.

ipuig

Which LS6 cam do you have, 01 or 02-04? The 01 LS6 did not use the lighter weight valves. The issue is not so much valve weight but valve stem length on the the 02-04 cam equipped LS6s. The valves were made longer in order to compensate for the smaller base circle on the 02-04 cam and maintain the desired lifter pre-load.

baxsom

would a longer pushrod compensate for that having that longer valve?

ipuig

I suppose that a longer push rod will restore the lifter's pre-load. I'm sure there is a reason why the designer decided to go with lighter valves with longer stems. It probably had something to do with a desire for increased reliabity and valve train stability at high RPM.

NatB

FWIW- GM no longer makes the yellow valve springs. Now they are blue, and I have no idea whether the specifications changed. I know because I ordered some- but shelved them and opted for PAC 1218's.

baxsom

I know I read a a few articles that said that they wanted to keep the same length pushrods across the board which is why the went with the longer valves. I had seen once that a 7.425 would take up the difference but I dont have enough parts in front of me to mic.

vettenuts

I don't agree. The 01 cam was smaller and I believe had a lower rev limit. The 02-04 cam was larger and had a higher rev limit. This was accomplished with stiffer valve springs and lighter valves. Both are required to control that cam's valve motion at the upper RPM. With the heavier LS1 valves, I don't believe valve control will be maintained at the higher RPM's.

bearcatt

The yellow springs were used on the LS2 equipped GTOs with non-sodium filled valves, however the GTOs had a less aggressive cam, with less lift, similar to the 2001 C5Z06.

So with that said, I will revoke my original response to the OP and admit that I must agree with you vettenuts.


If I was wrong I was wrong. The important thing is to give correct information.
OP spend more and go with at least the PAC 1218s.


The specs below speak for themselves.


LS6 Valve Springs
1.800"" install height @ 90# pressure.
1.250"" @ 295# pressure.


PAC 1218
Beehive LS1 Spring
OD: 1.290"
130 lbs @ 1.800"
318 lbs @ 1.200"
Lift: 0.600"


PAC 1518
Premium Nitrided Beehive LS1 Spring
OD: 1.290"
130 lbs @ 1.800"
337 lbs @ 1.150"
Lift: 0.650"


PSI 1511ML Beehive
O.D. 1.290"
I.D. .630"
Seat Pressure 130lbs@1.800"
Open Pressure 370lbs@1.175"
Rate Lb./In. 384
Max Lift .625"
Coil Bind 1.100"




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vettenuts

I am a huge fan of the PSI springs, although they can be a bit harder to find.

bearcatt

I found a vendor (non-sponsor) that has them listed for $90 less than the PAC1218s. Not sure if they actually have them in stock.

PSI does seem to have a good reputation, I wonder why they are so scarce.



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Eric D

Knowing what year you have is a very valid point.
LS6 Valve Springs, 2001 is not the same as 2002-2004.

Full Blue springs, part #1256117 are for 2001 only on the LS6.

Full Yellow spring is the new color and part number, 12586484 It is used on:
2002 – 2004 LS6
All LS3
All LS9
2005 – 2007 LS2

Pink Stripe Part# 12589774 for all LS1

Note these are the single spring part numbers. Kits of springs will have a different part number.

ipuig

You do not agree with what? The rev limiter on my 01 was factory set to 6500 RPM, I've had it as high as 6700 RPM when I was autocrossing without valve float, I brought it back down because it did not gain me anything.
I believe most everyone knows that the 02-04 cam has .025" higher lift than the 01 cam, ergo the smaller base circle and longer valve stems. You should have read my comments in post NR 10 before assuming that I don't know what is required to control valve motioin.

bearcatt

To throw a little wrench in the works... GM's latest LS6 replacement spring. They are all blue now, no more yellow.

http://forums.corvetteforum.com/c5-z...s-from-gm.html




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mchicia1

I decided to just go with a custom grind from AI with the PSI valve springs. It will be a baby cam for sure, as I want stock idle. Can't wait to install it.