I am not quite sure how much lift the stock L98 heads will handle, but I don't think they will handle that of a HC. Can anyone tell me what I would have to do to the stockers so that they will safely handle the lift? I am not building anything crazy here, just a little peppier motor.

Will

 

Have the valve guides cut down for stem seal clearance. As long as they are setting up to do that, you might as well cut the spring seats to a larger diameter so you can install real valve springs. It's one operation, either way. And as long as the heads are under the mill quill, there's little excuse not to pull the rocker studs and machine the stud bosses down. That way, you can tap the holes for screwed studs that will actually stay in the heads under those better springs and higher lifts. Whether you install guide plates is up to you, but you should machine for them either way, then install spacers if you are not using plates right away.

You probably should consider a good set of rocker arms while you're doing the project, since the stockers will flex under the higher spring loads and may not have adequate slot lengths for the higher valve lifts. My vote would be for anything except aluminum.

 

Wow, I wonder how much this would cost. Perhaps vortec heads are more practical than I had once thought. Thanks Vader

Will

 

Sad thing is you'll have to do the same thing to the Vortec heads! They are not much better stock.

I got a quote from a local machine shop (Indy) that does work for IRL.

They quoted me $80.00 to mill the valve guides and enlarge the spring pockets for Comp 986's. Also recommended locator cups (although I don't know why)?

Now you'd have to add more for guideplates and screw in studs. I'm forgoing the guideplates and doing the screw in studs myself. I'm also only keeping these heads for a year or two so not putting much into them.

Good luck.