School me on valve springs. And studs

littleredstroker · Apr 30, 2013

bringing this back up
Blown the pmr motor and have found a 120k mile forged block for 700$
have a TN turbo, arps and 910s ready to go in. I bought a set 0f .015 and a set of .030 shims not knowing exactly what I will need . so shimming them, where can i get one of those micrometers ? or is there a different way to measure ? calipers maybe?

907DAVE · Apr 30, 2013

Something like this:

http://www.ebay.com/itm/Comp-Cams-4929-Valve-Spring-Height-Gauges-/130819188666?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e756e67ba&vxp=mtr

You can find them cheaper though, that was just the first that popped up.

JD3020 · Apr 30, 2013

I got my micrometer from Summit, its a Pro-form brand, or something like that. Just throw the receipt away yesterday. It was only $40, worked just fine.

IDK what sort of installed height you're going for, but i used .060 shims only. I don't remember the exact numbers, but all of mine were only .005 out of the factory spec, and 0.60 put then around 1.45 installed height. Or something like that, like i said i can't remember the exact numbers. It worked out to be good for close to 140lbs of seat pressure. Thats about the only thing i can remember for sure. LOL

TARM · Apr 30, 2013

You have to shim to make up for wear period no matter what spring you use. Each cylinder should have the same valve opening and close rates as the others but sometime wear is uneven so one valve might need a bit more shim. The idea is to bring each valve to the same amount of open and close rates based on the wear. You measure the height without any spring or shims in there and then add the shim to get the same equal height (whatever that maybe depending on springs used)

I did a half way decent explanation way back when we were still all over at PSN. IT was specific to the 910 and stock springs. You can get more than enough spring pressure without binding unless you are going into compounds or nos etc.... Just take your time measure each one. Replace the seals with new ones as its cheap and you are in there. The seals have a built in amount of shim that needs to be included.

What I do is to buy a few assorted shim kits from JEGs and the micrometer. This way you can mix and match whatever thickness shims to ensure they are all at the same height if there is variation in wear. Two kits should be enough they are cheap.

I went and dug this old post up maybe it will be of some help:
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Originally Posted by TARM View Post
Actually I was just thinking about your number. Maybe your builder is not subtracting the .045" thick integral shim/seal. The one you need to pull before installing any extra shim. (The shims go underneath the seal as does when using the micrometer) Without that seal installed height is 1.810

As that is part of the stock setup I and I think others do not count that into the figures. We want to know the actual final spring height in a installed stock setup condition.

Stock springs with about 100K miles on them IIRC tested out in the 70s lbs. Not sure what the in new condition spec is on the stock springs.

Here are the specs for the 910 striaght from Comp cams:

Base install height: 1.850"
Maximum Coil Bind Height: 1.280" (the ones I measured were all lower than this.)
Inside / Outside diameter: 1.354" / 0.940
Spring Rate: 415 lbs

Install height : lbs
1.900" : 72 lbs
1.850" : 92 lbs
1.800" : 113 lbs
1.750" : 134 lbs
1.700" : 155 lbs
1.650" : 175 lbs
1.600" : 196 lbs

Actually I made a mistake in my writing of notes. The install height worked out to 1.74 The maximum without bind new leaving a small tolerance I figured out was 1.70. That was based on all new parts and the max coil bind height. That would leave a bit extra.

Install height: 1.810
Factory seal integral shim .045"
Spring install height with seal: 1.76"
Cam .410"
Max Coil Bind height: 1.28"

Competition Cams Spring 910:

Closed @ 1.760" = 130 lbs
Open (.410") @ 1.35" = 300 lbs
Distance to Max coil bind height: 0.70"
415lbs per inch rate

That is without accounting for any cam wear or valve train wear. I figure that would be variable. Also the compressed height is actually lower that is the max tolerance.

I just went thru all of this like you are just a few months ago so I am far from full of experience. I simply took a more to middle of the road level. I wanted more a bit more than stock height but did not want to get to close to the bind point even if that a maximum spec that they are likely below. Better be safe than bind a coil and break a rocker. At the same time with higher RPMS and and 2x stock boost levels I did now want the valves floating and smacking a piston as that would be far worst.

Most I think just slap them in there with either a .030 or .060 shim based on mileage and call it good without measuring. I, based on suggestion from others on here, purchased a spring micrometer so I could measure. As your builder is actually going to be measuring the heights I would think going with the stock height spec with the 910s makes sense. I forgot I had to take off the seal to get the micrometer on and then account for its height to figure actual point to max coil bind and actual seat and open pressures. But you now have the numbers for that I posted above.

If you at 125lbs seat pressure from what I have been told that is good for most typical setups.

1.75" of actual spring height gets you 134lbs so I would think you would be good for your planned use. But I will gladly defer to anyone that has more experience, which should not be too hard to meet.

Edited to add:

I found the stock spring specs. At 100K miles I recall someone measuring and only finding the stock springs only had pressure in the low 70 lbs range.

New this what I found for stock springs:

Closed Seat Pressure @ 1.76" = 110 lbs
Open Pressure @ 1.35" = 250 lbs
350lbs per inch rate

If you choose to actually measure spring tension and heights be sure to fully compress the spring a few times to allow it to take any initial set just in case. The measure. For most apps people do not do this.

I personally think stock springs, especially old ones, cause valve float that goes unnoticed until heads are pulled off.

TARM · Apr 30, 2013

This is just off JEGs as its easy to search and get links to. Get where ever. Sponsor etc..

These springs: Comp Cams#249-910-16

These Shim kits: Jegs Part #555-20591 (16 of each 0.15, 0.30, 0.60) Getting two would ensure you are covered for most possible scenarios but one can be good enough. But at under $20 each two seems worth it even if you happen to lose one. Easy to do for me.

This Micrometer will work and has the needed range: Comp Cams#249-4929 range: 1.6"-2.2" or Proform#778-66902 range:1.6"-2.1"

Make sure you plug all the holes in the head when doing this so if those keepers fall they do not end up in the engine and lost or you bobbing with a magnet.

If I got anything wrong on any of the above someone please correct it as I wrote this stuff years ago.

littleredstroker · Jun 10, 2013

Reading through this and a few others as I'm doing them, and I'm just getting more confuses on what height to go with.... Been going 1.750 installed , does that sound right ?

sent while looking at a hole in my block

rascal · Jun 10, 2013

sub'd

chris1978 · Jun 10, 2013

littleredstroker said:
Reading through this and a few others as I'm doing them, and I'm just getting more confuses on what height to go with.... Been going 1.750 installed , does that sound right ?

sent while looking at a hole in my block

Installed mine the other night to Swamp's recommended 1.780".

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