jmX

The only heads I've ever heard of the spring pocket busting through on are the LS6 heads. Both ARE and MTI have busted through on a few sets. When that happens, it breaks into the intake port, and you'll burn copious amounts of oil.

If you are just boring out the pocket to fit a 1.43" spring and you dont have LS6 castings, you should be good to go. Mine have been perfect thus far. If you are going over a 1.43" spring and need to take out more, you may be going into uncharted waters.

Jantzer98SS

iTrader: (54)

You could use double springs, but why? I'm running 981-16 springs (probably the ones that comp recommends for your cam) with a very similar lobe that's on your cam. I have had 0 problems. My recommendation is to shim up the 981 springs to get a little more spring pressure out of them. Otherwise just use the new 918 single Comp springs. Don't go double springs with your combo, it'll just cost more and make less power. It's not the horsepower level that determines appropriate spring pressures, it's a combination of valvetrain weight, cam lobe design, and rpm's.

FWIW, I've run hundreds of passes with my 981 springs, push 400+RWHP, and shift at 6800 rpm's.

SStrokerAce

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Jantzer98SS:
<strong>It's not the horsepower level that determines appropriate spring pressures, it's a combination of valvetrain weight, cam lobe design, and rpm's.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is true. Who ever told you the spring rate is determined by the HP level is wrong and doens't have a grasp on whats going on in there.

BTW have you ever noticed that spring rates on engines change when the cam or valves are changed. The LS6 01-02 vs. LS1 vs. Comp XE-R, HP levels could all be 450hp because of the displacement and headflow, but the cams could all be different. The more aggressive the load the lighter the valve system or the stonger the springs or both.

Bret

Jackyl_30

I was mistaken. He wants to go 80 thousands wider, not deeper.
Just found out also that the reason we want bigger springs is because the supecharger keeps addition pressure on the valves (blowing air to the top of the valve making a downward force). It does make sense that this happens and I can not understand why I have not read about that anywhere. This definately needs to be in the equation when getting springs for a high pressure engine.

Freak

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Jackyl_30:
<strong>I can not understand why I have not read about that anywhere.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Probably because the small amount of pressure increase isnt much of an issue most of the time.

Crazyquik

Forced induction engines are harder on valvesprings than naturally aspirated engines all else being equal. What rpm are you going up to? I'd go with a double spring, mainly for safety. I'd rather lose a couple hp due to excess spring pressure than do the piston to valve collision when a spring breaks. Just dont go too high with the spring pressure, or you'll collapse a lifter.

J.

LS1derfull

Just wanted to add higher than needed spring pressure wears out valve guides much faster,it taxes stock rocker arms(deflection of rocker is probably key reason needle bearing retainers fail)
valve job is distorted quicker,valve tip and stem wear quicker, lifter plastic retainers wear faster and lifters get slop causing them to try and rotate, timing chain wears and gets slop in it more quickly causing retarded cam timing. These items are all important to consider when setting spring presssures, dont take this too lightly .

rumbleme

Unless your engine is being built by and ARE type you should stay with the spring supplied by the mfg. They know there product and supply springs that are designed for the cam they come with.

If you don't believe this then contact your cam mfg. and ask them they are the experts.

Jackyl_30

I do have to admit that my intial reaction to the Comp Cams 63-26918-16 was that they did look a bit "weak" for what I am doing.

LS1derfull

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Jackyl_30:
<strong>I do have to admit that my intial reaction to the Comp Cams 63-26918-16 was that they did look a bit
"weak" for what I am doing.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think #918 is good for your application and i think its pressures are getting close to max you can use before deflating hydraulics.

<small>[ April 03, 2002, 08:29 PM: Message edited by: LS1derfull ]</small>

Jantzer98SS

iTrader: (54)

You're only running .535 lift, it's not an aggressive lobe by any means. Trust me, I'm running the 981's at only 115-120lbs on the seat. You just don't need a double spring. The 918's are probably even overkill, but if you want peace of mind...go that route. Any more spring pressure than the 918's and there's a good chance you'll run into valvetrain failure somewhere anyway.

The LS1 valvetrain is pretty light and with the shaft mounted rocker system, you don't need big ol honkin' valvesprings like the old schooler's think we need.

My $.02

JPR

Why don't you just install Isky 295D drop in's springs and call it a day? We are running 620 + FWH with them FI, little over kill for that low lift but if it's piece of mind that you are looking for thats the route.

Jackyl_30

My stock 98 heads are getting re-worked. I am have a supercharged 382 done and my question concerns the area where the springs sits on the head. The springs that I got from Comp Cams for my cam (218 / 224 .527 / .534 114 LSA) are really not much better than the stock ones. It has been determined that I need bigger springs or possibly a rev kit for the kind of power I will be running. My machinist says that a bigger spring can probally fit in there. They just need to mill out 80 thousands. Is ok to mill out 80 thousands? It is not much, but sometimes not much is all it takes. The concern is milling into the water jacket or the spring eventually punching through. So how thick is that area where the spring sits?

<small>[ April 03, 2002, 12:58 PM: Message edited by: Jackyl_30 ]</small>