[bb400ho]

someone changed the rocker studs and nuts in the 69 gto im working on. i was getting checking out a miss and fornd #8 cylinder had no compression. after checing it out neither the intake or exhaust valve close all the way when the other is open. if i back the rocker studs off a little the compression comes in line with the other cylinders. are the rocker studs are larger than the originals and the nuts look like lock nuts. are these adjustable like the chevies? the nut on the left is the new one the other are the nuts i found in a box withe the old studs.
thanks bryan

[Mr. P-Body]

Yes, "adjustable" like Chevy. We get "zero" lash (pushrod will turn with SLIGHT resistance) and add 1/4 turn.

Jim

[BVR421]

nut on left is locknut to make adjustable, appears to be 7/16"?
the nut on the right is a factory Pontiac shoulder nut, 3/8" for factory studs, which is to be torqued down to 20 ft lbs. That is for bone stock factory original valve train. Once you start changing cams etc you need to adjust the lash and the stock nuts have no means to hold other than torqued down tight. So then you use a lock nut or a fancy aftermarket deal with a setscrew.

[J_JAMNIK]

Sometimes even all factory stuff on the heads needs to be refreshed. It is possible that you have a burn or worn valve or valve seat if the valves don't completely seat. In higher compression engines you will find out quick if this is the case when you really put your foot in it. The heat on the lip of the intake valve will detonate the fuel/air mix in the intake manifold even if you have adjusted the rocker nut.

[bb400ho]

thanks for the info. it runs much better on 8cyls.
thanks bryan

[74Grandville]

if it was my engine, I would buy some poly locks.