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Discussion Starter · #1 ·
How much can be milled off head before it is necessary to shim cam towers? I'm thinking anything up to .050 would not require shimming, what do you think?
 

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Any time you mill the head you put slack into your timing chain, thereby changing your cam timing. Depending on how much you shave will determine the amount of cam timing alteration. An adjustable cam gear will allow you to dial in your cam timing if you choose not to shim the cam towers.
 

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> How much can be milled off head before it is
> necessary to shim cam towers? I'm thinking
> anything up to .050 would not require
> shimming, what do you think?

Shim it. Shims come in .020 thickness, so obviously anything more than that should be shimmed accordingly. (i.e. 2 sets if you shave it 50 thousandths) they're only about 10 or 15 bucks per set, so it's not worth it to screw up your cam timing on account of 30 bucks.
 

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Discussion Starter · #4 ·
> Shim it. Shims come in .020 thickness, so
> obviously anything more than that should be
> shimmed accordingly. (i.e. 2 sets if you
> shave it 50 thousandths) they're only about
> 10 or 15 bucks per set, so it's not worth it
> to screw up your cam timing on account of 30
> bucks.
Shim it is good advice but I think there is more to it. Lifting your cam by using shims moves the cam away from the valves and reduces the amount that your valves open. This reduces V/E and hence performance. How much is a matter for experiment. I think that someone, perhaps Brian Little on his page has a fix that you can use in combination with shims to prevent the lift problem. Of course one way to do it is to put in a higher lift cam. I almost hate to say it but my nephew is a machinist and he made me an adjustable cam gear and says that he will make them for others too.
 

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> Shim it is good advice but I
> think there is more to it. Lifting your cam
> by using shims moves the cam away from the
> valves and reduces the amount that your
> valves open. This reduces V/E and hence
> performance. How much is a matter for
> experiment. I think that someone, perhaps
> Brian Little on his page has a fix that you
> can use in combination with shims to prevent
> the lift problem. Of course one way to do it
> is to put in a higher lift cam. I almost
> hate to say it but my nephew is a machinist
> and he made me an adjustable cam gear and
> says that he will make them for others too.

Yep, good point, I forgot to mention lash pads that are the right size to offset the fact that the valves will be further away from the cam with the shims installed.
 
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