Did you have to shim rocker arms with SBC valves?

sizemoremk

Registered User
My machinist was not sure yet and asked me if I new if they had to be shimmed or something...

Do these shims have to be custom made, or is there a standard size for these?

If I were to run the 1.8 pedistal mount rockers does this make any difference?

Thanks!
 
sizemoremk said:
My machinist was not sure yet and asked me if I new if they had to be shimmed or something...

Do these shims have to be custom made, or is there a standard size for these?

If I were to run the 1.8 pedistal mount rockers does this make any difference?

Thanks!
No offense to your machinist, but that is a question that can only be answered by him. It depends on your cam's base circle, your pushrod length, how much both the block and heads have been decked, rocker arm manufacturer and the tip height of your valve. Obviously all of those things are open to variations so only the installer can answer those that question with anything that resembles accuracy. :)
 
If you get bolt down rockers make sure to get the right lenght bolts. SBF pedastal mount rocker shims should work fine. As far if needed or not you will only know once its all put together.
 
XR7 Dave said:
No offense to your machinist, but that is a question that can only be answered by him. It depends on your cam's base circle, your pushrod length, how much both the block and heads have been decked, rocker arm manufacturer and the tip height of your valve. Obviously all of those things are open to variations so only the installer can answer those that question with anything that resembles accuracy. :)

Well he did the vlavejob without re-assembly, because I had too pick them back up to apply the TBC coating to the CCs and ex ports.

He did not assemble the heads yet, but it looked like the ex valves stems were a little taller than the intakes. He just asked me if I had adjustabe rockers or if I was gonna use the stockers, and said I might need to shim them...

I was just wondering if others have had to do this.

As for the cam base circle, does this get changed on a regrind? I got the catwithboost cam, and the card don't have that info on it... Should it be all that differnt?

ANywyas, I am paying them to setup the heads, but now that I think about it, would this only include shimming the springs for the correct hight?

If so, would I have to reassemble everything, then take it back for the rockers to be adjuted/shimmed? Or should he be able to mathematically calculate this? Or is this somethig that should be figured out by me?

I was planning on putting these heads and cam on my currect motor till I get everythng tuned up, etc, etc... So should I get some kind of adjustable pushrod to find out what length I need? It's likely that I will need two different sets of pushrodds for the old and new motors, since the old block hasn't been decked...

How would I get a rough estimate for pushrod length, or wether I need to shim up the rocker arms? Wouldn't the engine have to be oiled up (or lifters soaked overnight) to do this anywyas?

I'm confused:confused:
 
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Step one is to set the tip heights. This is something the shop does during assembly of the heads. Hopefully they can get both intake within the stock range (1.920-1.950). If so then all that remains is to mock things up and check pushrod length. Most likely 7.200-7.300 but you'll have to wait and see. Pushrod selection is always the last thing you do. If you can't get exactly the right pushrod length or if the valve tip heights vary too much then you have to use shims.

I always include shims in my cam kits because not all cams are the same and not all rockers are the same - and if the heads or block have been milled you just never know exactly until you do a mock up.
 
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