hotroddave40 originally told us about the use of GM V-6 springs, which he said are a drop on, no machining required. I've been doing a little investigating. first of all, the specs I found on rockauto is this:

<a href="Sealed Power VS-1642 spring specs" target="_blank">http://info.rockauto.com/SealedPower/VS1642.html</a>

if you do the math, this yields a spring rate of 365 lb/in. backsolving for the free length yields a 1.898" free length based on these specs.

NapaOnline lists the free length as 1.94".

the Sealed Power VS1642 cross references to every GM 3100, pushrod 3400, and pushrod 3500 V-6 from 1993 to present. armed with this info, I went out and yanked a few (and the retainers) from a '94 grand am in a local junkyard. I have a friend where I used to work that runs the test lab there. he did some testing for me to verify the sealed power specs.

his findings on the sample I gave him:

Free Length: 1.875"
Travel before coil bind: .81"
Coil Bind Height: 1.065"

Spring Rate: 330lb/in

sounds like a definite possibility, the calculated spring rate was slightly higher than the comp 901's I have on my LA headed 360 now, the measured (12 year old spring) was slightly lower. but the measured used spring had a higher spring rate than all the comp cams beehives (pn 26995 looks to be essentially a "drop on" spring for a magnum head), albeit the GM spring is a little light on seat pressure, which could be adjusted with shims at the expense of lift capability. it would be interesting to get my hands on a MP R/T spring to do a comparison test, since MP give absolutely 0 specs on that

and now the the cheap part: the GM part numbers for these components are 10166343 for the valvesprings, and 10166344 for the retainers. if you go to the site www.gmpartsdirect.com and type those numbers in, you'll find the springs are $4.71 each, and the retainers are $1.52 each, compared to the manciniracing.com price for the MP .525" springs and retainers at $9.50 each fo the springs, and $8.95 each for the retainers.

so you can get brand new retainers and beehive springs for ~$125 to your door (gmpartsdirect estimates the shipping at ~$27!)

attached is the force curve from the instron he tested the springs on.


this weekend I will install a set on the magnum heads I have under the workbench and take pics for all to see. I'll also do my best to measure the current installed height of the stock springs vs. the installed height of these springs (using the 3100 retainers) in case of any changes there, so stay tuned.