I have a solution for guide plate problems ... throw them away.
If your head is already machined for guide plates install the Yella Terra #YT6321 rocker arms. The rockers mount solidly to the head on their pedestals and utilize a push rod cup adjuster for valve clearance or lifter pre-load adjustment.
For those of you whose heads are not machined for guide plates, don't bother with having them machined. Yella Terra #YT6015 rocker arms have pedestals designed to fit in the slotted rocker fulcrum mounts.
Not only does this eliminate all the possible problems caused by guide plates, it also allows you to utilize tapered push rods.
-G
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.