RX-Ben

I did a search but couldn't find anything helpful.
Setup is a stock '01, used for street and NASA time trialing.
I have read that the stock valve springs are prone to float, which is something I'd like to avoid if I raise the rev limiter to 6500 or so to avoid shifts.
I was thinking of mild springs (beehive, rated at <.6 lift, on the lower end of seat pressure) as an insurance policy.
Any thoughts?

Thanks.

AU N EGL

comp 918s or pac 1218s are both good choices.

geerookie

I also highly recommend replacing the push rods if you replace the springs. I just finished doing mine and I found 2 significantly bent push rods. This is a common problem. The factory one's a much weaker than aftermarket.
Comp Cams 7.4 are a stock replacement length. If you haven't changed rockers or anything else the geometry should be fine with these.

travisnd

You won't bend a pushrod unless you mechanically over-rev the motor. And in that case it's nice to have the stock pushrods act as a "fuse" of sorts. OEM "yellows" (the 2002-2004 Z06 springs) are only $55 a bag from online distributors like Scoggins-Dickey and GMPartsHouse etc.

RX-Ben

My understanding is that stock length ("gauge length") is 7.38 or 7.385 - anyone have anything different?
This is relevant as I'm considering Smith Bros oil restricted pushrods.

travisnd

You are correct.... the stocker is 7.385... the 7.4s are a smidge longer.

sperkins

Aren't aftermarket valve springs a points hit for NASA TT?

RX-Ben

non-OEM valve springs and retainers are specifically mentioned as 0 point mods (I(c)(21)).

BUT - looking at the updated rules - non-OEM pushrods are now +6pts.

Also - anyone have any interpretation of rule C.17?

"Modified or non-OEM camshaft(s), rocker arms, push rods, or cam timing gears +6 (for one
or more)"

-- a trunion bearing upgrade is not a mod to the rocker arms - no reason that there should be points for that, correct?

Thanks.

travisnd

Not sure why pushrods would take points, but with rocker arms you could put a higher ratio arm in and get a little more power so long as you don't encounter P/V clearance issues.

A trunion bearing upgrade is a mod.... it may not help performance and only longevity, but it is a modification. Just like enlarging the hole on a stock airbox lid to mimic an '02-'04 airbox doesn't increase performance any more than finding an OEM '02-'04 lid, but you still have to take points for a modified intake.

RX-Ben

I would argue that the bearing upgrade is not a mod b/c the stock geometry is not altered and neither is the rocker arm, which is the subject and point of the rule. The bearing is a separate piece altogether. Other longengevity mods, like upgraded discs, are 0 pts.
I'll check with Greg.

AU N EGL

Shhhhhhhhhhhhhh

travisnd

I'll put money on Gregg telling you it's a mod. In the literal sense you are modifying the part. What might only be a longevity mod on your car could be a performance mod on another car.

drivinhard

it's never stopped him on anything else

RX-Ben

No points for the trunion bearing upgrade per the following from Greg:

Ben,

I think that as long as the rocker arm geometry is not changed and no change in lift, etc. then it would be ok under these No-Points rules:

No-Points:
18) Engine rebuild with head shave, block decking and 0.020” overbore—provided
that compression ratio is not increased by more than 0.5 and displacement is not increased by greater than 1.49%. Forged pistons and internals are legal; however, points must be assessed for de-stroking, and/or increased displacement and compression ratio if greater than the limits listed above. (Note: 0.020” overbore with OEM rods and overbore pistons will yield an increase in displacement of approximately 1.1% for most engines.)
19) Engine balancing and blueprinting

geerookie

Hmmmmmmm........
I'm confused! You are allowed to shave the heads and deck the block...these can/will change the geometry of the valve train.
But you aren't allowed to change the push rods to maintain proper valve train geometry?
Maybe there needs to be an amendment that makes push rod changes that don't change the factory valvetrain geometry a 0 point change.

RX-Ben

Yes - the rule is overbroad as written. Until it is revised, rulings on an individual basis will be necessary - seems like it should be ok.

kmagvette

So, if you are not encumbered by rules...is there any advantage that dual springs yield over single? Say, 921 vs 918.

The goal is reliability on an almost dedicated road course track car - C5Z, stock LS6; it gets a good beating.

The 921s have a substantially higher spring rate but looking at the spring tables it appears that the delta in spring load within the operating lift range (stock cam) is approximately 10% higher on the 921s. Is that 10% too much?

With either of these kits I will be replacing the push rods while I am in there.

RX-Ben

I would not go with high spring rates (like duals offer) as they abuse the valve seats for no gain. I'm not sure how to quantify how much spring rate is enough to prevent float, but I am thinking that a modest increase over stock should be fine and not lead to too much additional wear.
Non-oem pushrods will cost +6pts in NASA (w/o a private ruling), if you are subject to that rule.

kmagvette

I know I need to replace the springs, so I am starting to get my learn-on with respect to what work/product is most appropriate for my needs. After taunting myself with the possibility of a mild cam upgrade I came to my senses and decided not to pull the pin further out on the grenade under the hood.

The engine is bone stock (recent Katech timing & oil pump chain and ATI Damper), 30K, about 18K track miles. LG SuperPro headers and a Halltech Venom 2 to help the breathing. I am toying with having the heads CNC ported, but will probably just leave them alone.

I have seen other posts touting the benefits of nitrided springs, etc. and am still sifting through the good and BS opinions out there. I agree that adding seat/spring load for no gain is bad. The rockers, bearings, push rods, lifters, and ultimately the cam all bear added burden for no reason.

My sanctioning body is my wife so any modifications I do happen in the dark of night with no paper trail. When/if I get busted there usually is a punitive furniture penalty levied against me which, in future discussions, is characterized as a "we" expense.

geerookie

"Our" living room has all brand new stuff in it as of 3 weeks ago! The only original thing is one of the small lamps that has some sort of sentimental value. Call me, the valve spring change is easy and not very time consuming. I have a spring compressor you can have also.