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Author Topic:   z28 springs
dode
Member
posted February 03, 2003 10:49 AM
We have midwest motorsports heads with .550 lift Z-28 valve springs. Can anyone tell me what the spring pressures are? The cam I want to run requires 125 psi on seat and 325 psi open. It is a hydraulic lifter cam with .509" of lift. Can anyone help me out? Thanks.

John

KPLugnut
Member
posted February 03, 2003 01:11 PM
If they are Z28 springs, they won't handle that much cam. I'd throw out an educated guess that they'll be at the MOST about 110lbs at the seat and won't have that much nose pressure. It's also been my experience that those z28 springs don't hold what seat pressure they have and the motor will soon start to skip and float the valves at about 5000rpm (or less).
If you're looking for seat and nose pressures like that, you'll need a drop-in spring that is designed for nearly .600" lift before coil bind.
Drop me a line if you need help finding them.

Hope that helps,
KPLugnut


dode
Member
posted February 03, 2003 01:13 PM
yes, I would very much like some guidance. I believe we had a problem with valve float last year, and I don't want it to happen again this year. Thanks. You are always a big help.

John

KPLugnut
Member
posted February 03, 2003 01:20 PM
PM comin' at ya.


istock59
Member
posted February 03, 2003 01:39 PM
JR Motorsports has a drop in, Z28 "type" spring, that will handle 600 lift. Rates are similar to what you're wanting. Reasonably priced. I used them last year and replaced 1/2 way thru the season.

There's also a Crane H11 spring that is VERY nice, that should be around those rates. Quite a bit more expensive, but will last for a LOT longer than the cheapies...


dode
Member
posted February 03, 2003 02:00 PM
Thanks for all the help guys. I do have another question. What is the spring length at "seat pressure"? Also, at the "nose", is the spring height just seat pressure height minus the valve lift of the cam? Thanks a bunch.

John

istock59
Member
posted February 03, 2003 02:11 PM
Your spring length at seat pressure just depends on what height you install it at. If I remember right, standard SBC installed height is 1.70". But you can easily change this with offset keepers, offset retainers or by machining the spring pockets deeper.

Yes, you've got the nose pressure length figured right.

dode
Member
posted February 03, 2003 02:29 PM
As far as I know, everything is stock on the heads as far as hardware goes, except for stainless valves and the springs. I will attempt to measure them and see. I will see how it compares to 1.7". Thanks.

John

STREET16
Member
posted February 03, 2003 02:37 PM
Speedway motors has a set for about $40, PN 577-810107. I have used their $25 springs, PN 180-671515 with a .535 lift solid lifter cam and never had a problem, but according to your specs they don't fit the bill. Beware of putting to stout a spring in. you can wipe out a lobe.


dode
Member
posted February 03, 2003 02:48 PM
I was just reading the specs off of the crane cams website. The cam I am looking to run is a Blue Racer WG-1051. It specifies 125 lbs seat pressure and 325 lbs open. Comp cams has an almost identical cam, the 12-213-3 (292H), and they recommend dual springs which require machining. The spring they recommend is 132 lbs seat pressure and 280 lbs open. I just want to find a setup that will be reliable and not give us valve float like we had last year.

John

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