Head resurfacing question

DougD

Registered User
Hi Gang,

Had a valve job done on this engine I'm building. I asked that the heads be resurfaced and the machine shop removed .004".

Is this likely to present any problems with push rod length or rocker arm geometry? I'm thinking "no" but I see from browsing the archives that this is a rather critical area.

Thanks for any advice

Doug Dwyer
 
Head resurfacing needs to be done to get the proper seal and take away any slight warping. so your good i have mine surfaced when i did the hgs.
 
Head resurfacing needs to be done to get the proper seal and take away any slight warping. so your good i have mine surfaced when i did the hgs.

Right, thanks. I just wasn't sure how much could be removed before I might run into geometry problems.

Thanks
DD
 
Correct me if I'm wrong, but I think the first problem you would likely run into is getting the lower intake to seal properly. Not sure at what point though.
 
Correct me if I'm wrong, but I think the first problem you would likely run into is getting the lower intake to seal properly. Not sure at what point though.


Nor am I. In fact I hadn't even thought of that possibility yet. For an intake fit problem I would think more like .020-.030 would be a problem but that's just a guess.

Thanks
DD
 
Nor am I. In fact I hadn't even thought of that possibility yet. For an intake fit problem I would think more like .020-.030 would be a problem but that's just a guess.

Thanks
DD

The only thing to take into account here is you are assuming the factory dimensions were spot on. you likely won't have a problem with geometry or sealing but you will certainly want to check it. Considering the factory can often produce parts at the extreme edge of within tolerance, you want to double check things after you change something.
 
four thousandths is very little to remove during a resurfacing on the heads. figure this, get a dial micrometer and wind it out to .004"s. look at the small gap that it indicates. usually there has to be quite a bit more surfaced off the deck of heads before manifold fitting issues arise. a friend of mine some years ago was building a mouse motor and had the heads angle ground around .075 or so and had the intake surface trued up back to the original angle. now keep in mind this is a relatively extreme example, but illustrates an amount that was done and had to be corrected.
BTW, has anyone here experimented with o-ringing heads to alleviate head gasket failure? just wondering as i might try this when mine goes POP!!
 
four thousandths is very little to remove during a resurfacing on the heads. figure this, get a dial micrometer and wind it out to .004"s. look at the small gap that it indicates. usually there has to be quite a bit more surfaced off the deck of heads before manifold fitting issues arise. a friend of mine some years ago was building a mouse motor and had the heads angle ground around .075 or so and had the intake surface trued up back to the original angle. now keep in mind this is a relatively extreme example, but illustrates an amount that was done and had to be corrected.
BTW, has anyone here experimented with o-ringing heads to alleviate head gasket failure? just wondering as i might try this when mine goes POP!!


I had the shop take a full hundred-thou of one of my Jaguar heads once ! But that was a different kettle of fish. :)

The service manual is emphatic that no more than .010" be removed without mentioning what happens if you go further, although various ideas come to mind. Anyhow, I wouldn't have thought twice about .004" had it not been for what I've been reading in the archives about pushrods lengths and geometry, which seems to be more of an issue on these engines than I'm accustomed to.

Thanks for the reply :)

DD
 
Pushrod geometry has a tolerance +/- at least .030" so it will be awhile before you run into that problem.
 
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