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cam geometry question


yo2001

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Okay, first post here from me but here it goes. I'm going to shave the head .030-.045 to bump the compression this summer. I'm planing to use the cam tower shims to get the cam geometry back to the original. My question is do I need to get a thicker set of lash pads?

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Guest norm[T12SDSUD]

Assuming you are not exceeding .460" total valve lift with your cam the info below applies.

 

Hey Yo, if you are gonna just shave only .040" you can get by without using cam shims if your chain and tensioner are fairly new.

 

If you do decide to use shims, stay with no more than .030" worth of shim and that way you can retain the stock lash pads.Your wipe pattern will be off center with the shims but that is OK.

You will actually end up lifting the valve a little bit more and get slightly more power.

 

I use .030" worth of shim and stock lash pads with no problems.

 

Later,norm

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Hey Norm. Thanks for the reply.My cam is exceeding .460" lift. Here is the spec:

 

Int. Duration (Gross) 274deg

Exh. Duration (Gross) 274deg

Int. Duration (.050") 234deg

Exh. Duration (.050") 234deg

Int. Valve Lift .488"

Exh. Valve Lift .488"

Lobe Seperation 107deg

 

I don't think I would have a valve/piston clearance problem because I've ran shaved head and flattop pistons before with this cam. Now I'm running N47 and dished pistons. I've hear I could get more lift from forwading the rockerarms but i don't know if my springs will like that. My cam is lifting high. It's already about to bind. That's with the high lift/pressure springs. I'll measure the springs' max lift at the head shop I suppose. Thanks for the info.

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All you have to do is increase the thickness of your lash pad by the amount of shim you use. If you do not have different lash pad retainers, then you cannot go thicker than .160, and I think the stock one's are .133.

 

I once had a crower regrind in mine and a milled head and I had my cam towers shimmed up 75 thousandths, and I had .280 in thick lash pads. That was a sweet cam.

 

Send me an email at the office and tell me what the particulars are about the cam, etc, and I think we can come up with a solution.

 

Lockjaw

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