From everything I have read and heard, when you install guide plates on an engine that was not originally set up for them, you have to machine the stud bosses down the thickness of the plates - 0.125" in my case. You cant use longer push rods, otherwise you change the geometry and angle of where the rods contact the rockers, resulting in premature wear. Is this what everyone else has heard? Looks like I have to pull the heads off and take them back to the shop, dammit... I am building a motor and have installed summit 1.6 non aligning billet roller rockers, Comp Cam 510/510, dual springs on top of L98 D port aluminum heads. This is on top of an 89 roller block, 4 bolt main, bored .20 over with forged crank, CR's and steel pistons....

Generally so, yes.

Imagine if you will, the rocker arm in the engine. One end sits on the valve, and one end sits on the push rod which in turn sits on the lifter.

Adding guide plates doesn't change any of that. The rocker still has to sit in the exact same place it was at before.

Now imagine adding the guide plate. What that does in effect, is to move the stud upwards through the center of the rocker, by the thickness of the plate.

As long as the rocker ball (or trunnion) can still slide down far enough onto the stud, and as long as the set screw of the poly-locks (if you're running those) still have enough threads to bite on inside the rocker nuts, then it'll be fine.

I'd suggest dummying up a couple of cylinders and seeing what you've got, and if you get lucky.

Those heads came factory with guide plates. Shouldn't need to cut the bosses down. Just don't use the factory guide plates as they are soft (if you still have them laying around). Need aftermarket hardened plates and push rods.

RBob.

Damn if I saw any factory guide plates. This was originally a ZZ4 crate motor, with 1.5 self aligning steel rockers. Never saw any guide plates when it was disassembled. I built a new short block and kept the heads (budget you know).
I already have the new 1.6 roller rockers, otherwise I would just buy a set of self-aligning ones. ANd I still need to buy a set of hardentd push rods as well.

you cant use guide plates on heads designed to run self aligning rockers unless you open up the holes for the pushrods

He'll be ok with those heads. They used guide plates on the early castings and dont have the tiny slot like the cast iron heads..
These heads have a HUGE open space for the push rods..

As a matter of fact they do.
If I knew then what i know now, I would have just bought a set of self aligning rockers. But the money is already spent, so I may as well keep spending it, lol

The heads are off, and it's going to cost another $100 for the machine work, $120 for a set of hardened push rods and $50 for the head gaskets.

Oh well, lol