valve guide purchase from Pelican

kodioneill · kodioneill's Garage

Why does Pelican only sell oversize valve guides for 83 3.0?

Joe Bob · Joe Bob's Garage

Two Rivers · 12-15-2011, 01:27 PM

I believe PEP has the best guides on the planet.

PEP stands for Precision Engine Parts.
I was told once that they supply most of the bronze silicon guides for most of the suppliers around the world.
Just got a set for a 59 Mercedes and my Porsche heads.
Its amazing what they have.

Flat Six · Flat Six's Garage

I believe it's because ideally the guide OD should be turned down (machined) to match the slightly-enlarged ID in the head. My understanding from reading about the process (not having done it myself) is that removing the old guides will open up the head enough that standard size guides are slightly too small.

HTH

john walker's workshop · 12-15-2011, 03:58 PM

i use standard guides exclusively. can't remember when i ever used an oversize, except on 914 heads. just find standard ones.

LUFTMAN · 12-15-2011, 07:24 PM

many machine shops do not replace guides but put inserts in the exiting guide and ream it to desired clearence. once you remove old guide and replace with new one the valve seat is far off and requires much more material to be removed to get the correct contact on the valve seat in the cylinder head. the seat does not lend to so much material to be removed thus you end up replacing the valve seat also. much more cost added to the job.

john walker's workshop · 12-17-2011, 08:47 AM

never heard of anyone actually boring out 911 guides to sleeve them. as far as the seat being off from the center of the new guide, that's caused by the worn guide allowing the valve to wear one side of the seat away. when new, they closed precisely on the seat. when the guide and valve stem wears so the valve is sloppy in the guide, the rocker action will push the valve a bit sideways and when it closes, it contacts the seat on the side toward the center of the combustion chamber and basically drags itself in. so when the new guide is installed and you begin to grind the seat, it won't clean by as much as 1/2 way around for a while. 3.2s are the worst for some reason. even if you could sleeve the guide, you can't compensate for seat wear. the guide would have to be bored on an angle.