Do I need guide plates?

[emutt]

I'm getting my heads changed to screw in rocker studs and was thinking of switching to full roller or roller tip rockers.

For heads with the close-tolerance pushrod slot, are guide plates still necessary?

This is for a '65 289. Since I have the heads off, I'm also considering putting in a new cam (but not anything too radical ), so the pushrods would face some higher pressures/lift.

Thanks.

 

[SoCalCruising]

Check your present rockers. If they are a standard "sled" type design, you will not need guides. If your rockers have rails on both sides of the tip (these keep the rocker centered over the valve tip), then I would use guides.

This is sorta second order. The close tolerance pushrod slots in the head generally negate the need for guides. Checking the current rockers is corroborating.

My source is a book, not experience. Others should chime in to agree/disagree.

 

[emutt]

Thanks for the input. Just for clarification, the originals were non-rail.

Also, would there be any reason to NOT choose the full roller rocker over the roller-tip style of rocker arm?

 

[SoCalCruising]

So long as your studs are long enough, I can't think of anything. You may have valve a cover height problem, but is solved with taller covers, or use double cork gaskets (two gaskets, one fixed to the cover, the other to the head).

 

[Loup-garou]

IIRC, you're not supposed to use guideplates on heads with the narrow pushrod slots. I can't recall where I read that, but I remember seeing a recommendation that the narrow pushrod holes be drilled out if guideplates were going to be used. That info might've come from Dave Williams over on the Fordnatics e-mail list.

I forget... how were the '65 289 HiPo heads configured - narrow slots or guideplates?

 

[Loup-garou]

I'm getting my heads changed to screw in rocker studs and was thinking of switching to full roller or roller tip rockers.

For heads with the close-tolerance pushrod slot, are guide plates still necessary?

This is for a '65 289. Since I have the heads off, I'm also considering putting in a new cam (but not anything too radical ), so the pushrods would face some higher pressures/lift.

Thanks.

Keep in mind that when the rocker mount pedestals are milled down for screw-in studs, the thickness of guideplates is often factored in. If you're not going to use guideplates, adjust the instructions to your machinist accordingly.

 

[D.Hearne]

No guide plates needed with the pushrod slots. As for full roller vs roller tipped, that's a no brainer. Full roller. Why spend almost as much for roller tipped, when you can spend a few dollars more and get the reduced friction of full rollers? There really isn't any frictional loss from roller tips. If you set them up and cycle the valve train slowly with std rockers, you'll notice that they already "roll" across the valve stem without the roller tip. The contact patch on them is curved for this, not a flat surface. The real gains from full rollers is from the roller trunions, they just about completely eliminate the friction that the std rockers suffer from that the ball and pedestal types generate.

 

[emutt]

Great feedback. Thanks everybody.

The main reason for the debate between roller tip and full roller was concern that the fixed movement of the stud pivot on the full roller would have less freedom of movement to compensate for any slight misalignments in the valvetrain, which might induce shear/bending loads on the studs. The ball-pivot seems a little more "flexible" in that regard. But then I thought about it a little more (a wonderful experience I should try more often ), and realized that the rocker tip isn't fixed to the valve, so some lateral sliding (though not optimal) can occur to prevent the stresses on the studs.

Anyway, thanks for all the input!