Piston to valve clearance

Awesome site!!! I would like to mill the heads on my 1998 Evo, but I don't know how much I can safely cut off. I have installed a SE 4 cam that will have more lift than stock. I would like around 9.5 comp. But if I shave the heads, say, .050 will I now have valve/piston interferance? Also, will I have to shorten my pushrods, or make adjustments to my intake??? Thank you.

[Mike]

EV's really respond to this change. Milling .050, the SE4 cam and using the stock .045 head gasket will be OK, but piston to valve should be checked just to be safe. You'll have to use checking springs in the heads so the hydraulic lifters do not bleed down, giving a false reading (we use a special tool and do it off the bike).

You will need shorter pushrods. Adjustables are the best bet here. It's possible you may have to shave the flange spigots on the manifold but not likely. Again, this should be checked and corrected as needed, easily done on a belt sander. If you mill more than .060, all the above will be required including relieving the piston valve pockets.
Thanks, Mike

I can't use my 1 piece stock pushods?

[Mike]

Not if you deck the heads. There is a chance the hydrualic units will be too low possibly holding the valves off their seats when cold.. The adjustables will allow you to account for this and possible base circle differences in the cams.
Thanks, Mike

If I only mill the heads .050 my pushrods will not have bottomed out my lifters yet right? I thought the lifter had at least .110 range. Can't I just slowly tighten down my rocker assy. to the head and if all the pushrods still spin freely when I'm done I am OK, right? Wouldn't it still be in the preload area of the lifter? Thereby retaining my lighter pushrods.

[Mike]

Your math is correct, but stack ups vary. I'm not saying you can't do it, but I must recommend what is correct and that would be to install either adjustables or "perfect fits". Rigidity is what's important vs. weight. The perfect fits are a tappered design and are much more rigid than stock. The adjustable's are not as rigid and also rub the covers which can cause noise, this is why we prefer to use the perfect fits when possible.
Mike

Thats cool, but where do I get perfect fit pushrods for an Evo?

[Mike]

I'm kinda in twin cam mode these days, my apologies. HD does not have them for EV's but your can get them from Zippers in kit form (cut to lenght) or order from Baisley Hi-Performance.
Mike