Adding Screw In Studs and Guideplates
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Joined: Jul 2000
Posts: 520
From: MD
Adding Screw In Studs and Guideplates
Unfortunately, I've always used self aligning rockers on everything I've messed with so I've never had to think about this before, but the current project looks like I'm going to use a biggish cam with some old school small block factory iron heads.
What machining is needed to install screw in studs and guide plates? I know that the tops of the stud bosses need to be machined flat, perpendicular to the stud bosses, but I can't seem to find consistent information about how much. I've heard everything from:
- taking off the equivalent of the height of the stud hex and the guide plate (that seems like a lot, it's probably over a 1/4", I'm worried that might not leave enough of the stud bosses)
- just cut the thickness of the guide plates off (that would leave the assembled height roughly that of the original boss + the stud hex, I'm not sure that will leave enough clearance for the rocker trunnion
- the other extreme end, as little as you need to get a flat/consistent surface (why they are labeled "machining may be required)- obviously, if i"m worried that "just the thickness of the guide plate" will not be enough, I'm almost positive that won't be enough.
What's correct? Is there some magic number that works? If I had a set sitting around already done, or a spare, similar assembled engine sitting around I could just measure/test fit everything, but I don't have either (I'm hoping to make it a weekend head/cam swap so I need to have them done before the engine is torn down).
What machining is needed to install screw in studs and guide plates? I know that the tops of the stud bosses need to be machined flat, perpendicular to the stud bosses, but I can't seem to find consistent information about how much. I've heard everything from:
- taking off the equivalent of the height of the stud hex and the guide plate (that seems like a lot, it's probably over a 1/4", I'm worried that might not leave enough of the stud bosses)
- just cut the thickness of the guide plates off (that would leave the assembled height roughly that of the original boss + the stud hex, I'm not sure that will leave enough clearance for the rocker trunnion
- the other extreme end, as little as you need to get a flat/consistent surface (why they are labeled "machining may be required)- obviously, if i"m worried that "just the thickness of the guide plate" will not be enough, I'm almost positive that won't be enough.
What's correct? Is there some magic number that works? If I had a set sitting around already done, or a spare, similar assembled engine sitting around I could just measure/test fit everything, but I don't have either (I'm hoping to make it a weekend head/cam swap so I need to have them done before the engine is torn down).
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Joined: Oct 2002
Posts: 255
From: Nashville
To figure out how much to mahine down you need to try to figure out where the rocker arm is going to sit on the stud and then take off however much material will allow the rocker to sit at that height and not run into the radius a the bottom of the new rocker studs. Typically I've taken off .300-.375 which would account for the thickness of the guide plate, the thickness of the hex flats and the radius of the stud bottom. Once you've removed the old studs and cut down the bosses just run a 7/16-14 tap straight into the holes as they are already drilled the correct size to tap. Be sure to run a bottoming tap down after the regular tap or you might not be able to get the new studs all the way in.
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