To shim or not to shim valve springs
 

This is the deal. Building a set of heads with double valve springs. Seat pressure is around 220lbs. After doing some measurements on a few installed springs I am finding that if I add anything under the spring (shim or locator cup) it takes me out of the margin of error for set spring height. These are cast heads and I'm kind of worried about the springs gouging the spring's seat. Would you go with a 15 thousandths shim anyway or just leave them out all together?

(They say you have 20 thousandths to play with. Spring height according to the cam card should be 2 inch. With nothing but the spring installed the average is about 1.975 to 1.980 which any shim or such will put them under.)

What keepers are you using? i have some that replace .050 worth of shim

CRN-99970-16 Valve Spring Retainers
Crane Valve Springs 96886-16
3/8 locks

you set the installed height correctly with whatever shim or no shim you need...

I.h.
 

Mark,

I your I.H. is 1.980” with the locator and no shim you have an easy fix. Exchange your keepers for a set of +.050” locks, bringing you I.H. to 2.030”, the install (1) .030” shim to make you final I.H. 2.00”.

If your I.H. is 1.980" on a bare head without the locator, you will need +.050" locks and and retainers in combination. Your last solution is to replace the valves with +.125" long

See attached spring chart for that spring in your application. Subtract your net, after lash valve lift from your 2.00” I.H. and you will find your actual spring force at max lift.

Bob


[ATTACH=CONFIG]536938[/ATTACH]

Lets
 

Try the spring chart again[ATTACH=CONFIG]536940[/ATTACH]

Alright now I understand. Just looked at a couple pictures of the set of heads I'm copying and they must have the taller locks installed as much as they stick out of the keeper and that's how they got enough room to put shims under the springs.
I guess no heads this week. Now to find locks. Anyone want to double check me before I order? http://www.summitracing.com/parts/hrs-93015/overview/

Thanks

PS, For future reference on the question of always having some sort of shim, rotator or cup between the spring and head. I take it's not necessary and you can put the spring right on the head with nothing in between? Is that only for low pressure springs or for any spring pressure?

My response of no locator or cup was to clarify where your measurements were being taken in post #1. I needed a reference for the calculations. It was not intended to suggest that the use of a locator or cup is not necessary. Before you purchase +.050" locks you need to verify your retainers. What are the cam dimensions for this, .050" and lobe or valve lift after lash?



Bob

at 220lbs on the seat,,you better use some type of hardened shim or your gonna eat that cast iron head up.also,do the springs fit tight to the outer edge of the spring pocket,if they do,you won't have to worry about the inner spring contacting the guide and eat that up too.at the spring pressures you have,I assume this is a solid roller.you can up the seat pressure a little and it won't hurt anything,better to have the head protected by something under that spring.

Bob,
I am literally cloning the Kiekhaefer 482 that I rebuilt last year to put both in Brownies old race boat. This is what they did. I couldn't figure out from pictures of my rebuild how they got two shims under the intake valves in their heads and yet I was using everything down to the last part number and coming up short from the start. Then you all mentioned the +50 locks and I had this picture of the K motor heads.

http://i21.photobucket.com/albums/b2...ntitled-15.jpg

Those locks in the picture are sticking a lot further then the ones I'm using on the clones heads. The thing I'm still trying to figure out is why they had only shims under the intake valves. But I guess the only way to find out now is to take the motor apart and that aint happening as good as it runs. lol.

http://i21.photobucket.com/albums/b2...ntitled-16.jpg

Maybe they used shorter valves stem on that side or something but they also didn't use anything under the exhaust valve spring either. Nothing but just bare metal to spring. That's why I asked in the first post. I've seen it all. Rotators, shims, spring had some sort of sheet metal cup pressed on it. Just looking for someone to say yes or no on spring to cast metal contact.
To be honest if is OK I may stick with what I've got cause I'm damn close to that .020 fudge factor already.

Crane Cams - Part #:138091 Mechanical roller tappet / Grind Number:TR-252/400-2-10, Basic Operating RPM Range:3,500-7,000 / Duration at 050 inch Lift:252 int./262 exh. Advertised Duration: 290 int/300 exh, Lift .680/.708