so i'm waiting to finnish my cam swap because i dont have a micrometer. is there any way around this? do i need my specific measurements to determine height? im sure 100's have done exactly what im doing, can i just use the known values? Ive never done valve springs before, so i dont know what all is involved.

my car:
1997 Camaro SS M6
installing GM 847 Cam
old pac 918 springs
comp cams pro mag nsa rocker arms 1.6
gm guide plates
7/16" studs
hardened pushrods.
new valve seals, spring seats locks and locators...

 

Surely there is a parts shop in nearby Savannah that sells a barrel mic to get the job done right. Take the time to set those springs up properly.

 

I was charged $25 for a machine shop to do my springs. I originally had 987's but went with 918 beehives at the last minute with my cam change,on my old set up. The installed height should be around 1.75 with about #145 on the seat-#350 open good for about .600-.610 lift give or take.
Are you asking on how to do this with out measuring? Not a good idea. Mine weren't perfect as each one varied a little from the other. Probably due to a mass produced head.

 

i'm just tring to figure out if i need to use shims. i ordered everything to match. and ive got stock heads and valves. how off could it be? my stock springs didnt use any shims. so basicly all i did was replace the stock parts with better ones, how could it not be fine?

when i ordered everything from thunder racing, they made sure i was getting all the right parts. for the cam and springs i already had.

they set me up with the seats, retainers, seals, and 10* locks, push rods, rocker studs and guide plates. never even brought up the idea of a micrometer or shims to set the correct height. should it already be the correct height?

thanks.

 

Thats the same thing i was thinking... why don't the factory use shims...
are the springs that other companies make not run thru a qc department to make sure all springs are the same?
also do you have to check install height for all of your springs or do you just check one and go from there?

 

i read that your suppose to check them all, and go with the lowest one to set the rest. something like that.

i went ahead and put them all together without any shims, even shoebox's site says he didnt need to use any shims with his setup. i'm sure if you have aftermarket heads, of have had your redone and every little bit of material removed or added will make you need the shims. but stock everything i dont think you would need any.

well just wait and see if im right or if i break my engine.

they look good on there.

I'm a little disapointed that my rocker arms didnt come with a allen wrench to tighten the poly locks. its a metris and all i have is standard. i think i may have the one i need around somewhere.

now i have to cut my valve covers, paint my intake and put the front cover back together and hooke everything up.

 

Not sure what the height requirement is for a stock spring.Are the stock springs and the 918 the same installed height?
My LE2 heads are a little older. They were set at 1.80 installed height. 3 yrs later the new height, as done by lloyd, is 1.75. How do you change the installed height with out shims? I believe he uses the stock lt1 locators.
If you did buy your stuff from Thunder and thats what they recommend, then install it that way. I didn't design my set up. I went to someone else for it and I set everything up as I was told to.

 

Setting springs up without at least checking it with a micrometer or pressure testing them is only asking for something to go wrong. Spend the $40 to $50 to get a micrometer or borrow one from someone. At least that will give you piece of mind but just slapping it together based upon some guys guestaments over the phone is a bad idea. Sure you could get lucky/close but the chances of that are slim. Being off by .020" is so small yet depending on set up, high cam lifts that get close to coil bind, could cause you to completely destroy your valvetrain. You cannot eyeball these kind of things.

 

GM does not typically shim valve springs because they maintain tight quality control consistency with the springs and the seats. Also they don't check each install height on an individual basis because the expected install height is very much weighted to the safe side at the expense of higher performance.

Install height should always be verified when replacing springs to ensure there are no potentials for coil bind which could blow a motor up. Mic's can be had for $40.00 on line.

 

The factory uses springs that are designed to work with the head as cast. There can be variations in the mass produced head. The factory relies on the fact that the mass produced parts are close enough in tolerance so that they don't spend any time measuring. Aftermarket spring heights vary by design and desired spring pressures.
As you modify and tolerances become more critical, measuring is highly recommended. If the heads have had any work done to them, valve stem height can be altered and therefore spring height. Each and every valve could be slightly different.

 

oh, ok i got you... it's more of a precautionary measure then a "i will get this much more horse power with this much more seat pressure"...

please see my example to see that i'm tracking...

ex. so if i use the mic and find that i have an install height of 1.780" and i want a closed spring pressure of 130# but when i perform my spring pressure test i find that the spring exerts 130# at 1.765" then i will need to install .015" worth of shims???

 

Yes, installing shims will increase the spring pressure when the valve is closed. Personally, I don't think that is as important as the pressure when the valve is open. You need enough pressure to keep the lifter on the cam, but not too much so that you collapse the lifters to the point of damaging them.