Valve Job

[Guest Shadow416]

I was wondering just what exactly a valve job consists of, because the company I plan on purchasing new camshafts from said a new valve job should be done. "Most important, a fresh valve job must be done by a competent shop at the time of cam installation. During this valve job, the machinist must be certain to keep the valve stem heights consistent; otherwise there will be severe damage to the lobes of the new cam." (thezstore.com). The valve train is one area I will always leave to professionals, so a rough estimate on how much this would cost would be greatly appreciated.

[BRAAP]

In its basic definition, a valve job consists of refacing the valve seat, reface the valve itself. Then measure the valve installed height and reface the valve tip till that valve installed height falls within spec. your less expensive shops don’t go through the trouble to set installed height.

 

Also, if the top of the head has been surfaced in it previous life, the cam towers should be shimmed back up how much the head was surfaced on the top to maintain OE cam height above the valve train. For accurate cam timing, the cam towers should also be shimmed by how much the bottom of the head was surfaced as well, if the top was surfaced as well, (should be done any time the head is overheated), but then there is now more clearance between the cam centerline and the valve stems, necessitating thicker lash pads!!!!

 

As you can see, even after getting the valve job “just right” in the first place, that is NO guarantee that the cam wipe pattern will be correct and the cam wont destroy itself in a matter minutes or hours. With most aftermarket cams, the opening and closing rates are so sedate, there is enough fudge factor that more often then not, as long as the valve job was done correctly, it will work fine, but you should never fall back on that.

 

If the cam you are purchasing has a recommended lash pad thickness, do NOT trust those lash pads to be the ones that WILL fit, for the all reasons stated above. When setting up the cam EACH and EVERY cam lobe wipe pattern SHOULD be verified regardless! With aftermarket cams ground on fresh blanks, the consistency during the grind process is pretty good. Reground cams are not as consistent, even lobe to lobe on the same cam, and depending on how aggressive the lobe profile, will dictate how much fudge factor you have in lash pad thickness which could mean 4-5-or even 6 different lash pad thickness for one head! The Rebello cams we offer have such an aggressive profile that there is typically only ONE lash pad that will fit each valve, ie. NO fudge room WHAT-SO-EVER and you can NOT cheat the wipe pattern as the wipe pattern takes up 95% of the rocker wipe surface requiring extreme attention to be paid to the wipe pattern. A cam that is ground in this manner is going to have more lift under the curve and perform stronger than any off the shelf aftermarket cams with comparable lift/duration figures that only use up approx 80% of the wiping surface and will allow for cheating the wipe pattern. That is whole other topic for another thread I promised to write last year, (I had best get it finished huh?)

 

 

Read through this thread linked below for a more in-depth understanding of the process involved in building, machining, and setting up cylinder head, pics included. Also, the SEARCH button is your friend...

 

Clicm ME for "how to" build and setup a custom L-6 cylinder head.

 

 

 

 

Hope that helps.

Paul