Read a few articles and but nothing was concrete on the subject, some say you have to shim to adjust height differences other said not necessary so what is it?
I know for a fact by adding shims to a valve you won't gain any height as the valve is already on the seat, but I do know a shim with make the spring shorter and give it less travel
So
School me on shimming and if it's really necessary or it's something that I can go quoth out. Talked to several engine builders and some of FTE members and said that the stock push rods can handle the 910-16 easily but to never exceed 40lbs of boost? True?/false? Need answers as I'm going to start putting this puppy together.

 

Do you have any valves that are higher on spring side?

​​​​valve seat pressure is important. No pressure means no cooling when resting on the seat and can add to leaking past the seat with out enough preload and cause floating on higher RPMs.

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To do it right you need to measure the height of each area from where the spring sits on the head to the bottom of the retainer. You put the retainer and keepers on and measure each one. I don't remember what the installed recommended height of the springs are but you then add shims to get to that number(shortens the spring, increases the pressure). FWIW I've seen stock push rods bend on a stock motor.

 

Thanks Darrin, I did some search and found the specs and the how to, now I have to buy or borrow a valve spring measuring tool, I think It's cheaper if I take it to the machine shop and let them sorted out just in case I don't want to fudge up lol....

 

I borrowed a tool to measure. IIRC, some said to just put in a 10 and a 5 shim for a total of 15 and go for it. When I measured and did all my springs some turned out different then that. PITA but worth it.

 

One of the "new" heads I'm using the intake valves sit a tad higher than the exhaust, so it's going to differ alot when it comes to shining, I have to buy a shim kit as this didn't come with them.

 

Installed height on a spring mainly changes when you do a valve job. Because you cut the head and the seat on the valve to "renew" them so that in turn moves the valve higher in the head. We always just used a 6in rule that read in 1000s you can get real close with 1
If your using new valves you still need to set the height on the springs. The springs I bought came with an installed height
Specifications:

Inside Diameter
0.94
Coil Bind Height (in.)
1.28
Open Height (in.)
1.35
Outside Diameter
1.354
Installed Height (in.)
1.85
Open Pressure (lbs.)
275
Spring Rate (lbs./in.)
380
Installed Pressure (lbs.)
85

 

Great info Queasy, thank you. And yes I'm using new valves but the same seats so some wear is visible.

 

We've done a few motors and just about every valve on each motor was different. I would not say to ignore it and just throw them in, nor would I say just throw in .XXX" and call it good. Each one needs measured and set accordingly to do the job correctly. It's a relative pain on the engine stand, even more nightmarish with the motor in chassis.

 

That's the good thing, the heads are off the engine and on my work bench, I called the machine shop and said he wil do it for $50 each and he will put in the shims, not bad. I

 

That's the way to go, I'd definitely have them do it.
It costs way more than that when your mechanic forgets to rotate the motor over and the valve drops out of the head onto the piston.

 

Adam, my only suggestion is to make sure that you and the shop clearly agree on what the final height should be. He should give you a written report, even if it's just scribbled on a cardboard scrap, showing the initial measured height of each valve and the final spring height after shimming. Just saying this because every single time I end up paying someone to do some work something ends up being not right. Maybe your luck is better!

 

I'm about to set up the heads for my 7.3 build and ordered the springs from Summit. What shims should I order?

Thanks

 

Sorry I can't help, machine shop did the springs and shimmed them.

 

Ok, pretty sure this is the correct kit - COMP Cams 4754 COMP Cams Valve Spring Shims | Summit Racing