valves keep backing off

butch27 · July 19, 2009, 08:22:00 PM

On my 302" Ford I've adjusted the hyd. valves 3 times and each time the engine runs about 20 minutes and starts missing. Pull the valve covers and the rocker arms are lose a fallen of the valve stems. What the Heck? Thanks Butch

tomslik · July 19, 2009, 08:30:57 PM

Quote from: "butch27"On my 302" Ford I've adjusted the hyd. valves 3 times and each time the engine runs about 20 minutes and starts missing. Pull the valve covers and the rocker arms are lose a fallen of the valve stems. What the Heck? Thanks Butch

PRESS-IN STUDS PULLING OUT OF THE head?
rocker arm nuts backing off?
lifter bad?

they'll all do it...

butch27 · July 19, 2009, 08:36:15 PM

Rocker arm nuts backing off.?

wayne petty · July 19, 2009, 10:18:59 PM

on 302 windsor motors.,... NOT "BOSS"

the only factory adjustable studs were 3/8 diameter studs with 3/8=24 threads at the top... one size from bottom to top of the stud....

late 60s and early 70's heads used a 3/8 stud.. but a reduced size thread 5/16-24 ... a stepped stud... this is not adjustable... it must be torqued down and any adjustments down by changing push rod length...

in the mid 70.... they started stamped steel rocker arms... with a tee shaped fulcrum... a metal channel for alignment of the rockers that the fulcrum bases fit into.. these are held down with a bolt... and must be torqued... non adjustable .. read my notes at the end..

later heads had a groove machined into the rocker arm mounting pads... the fulcrum bases fit into this... for alignment... these are held down with a bolt... and must be torqued... non adjustable again read my notes at the end...

notes... i am glad i remembered...

adjusting the cast iron rocker arm versions... with the stepped stud...
i have found that if the valves need to be tighter than the step allows... a trip to the plumbing parts section is in order... faucet supply tubes.. the old style... with brass washers and tapered grey seals.. the brass washers are just about perfect to put under the nut to drive the fulcrum down a bit more taking up the slack...

to loosen the adjustment... grind the bottom of the nut a bit... this will let the fulcrum sit a little higher ...

for stamped steel rocker arms... on aluminum fulcrums...

shims are available from Crane cams and others to fit under the fulcrums in the guide bar or in the slot to raise the fulcrum to loosen the valve adjustment...

to tighten the adjustment... on these non adjustable rocker arms... without buying the shorter pushrods... carefully grind the base of the fulcrum.. this shortens the fulcrum... tightening up the valve adjustment.

when building a fresh motor or putting in a cam and lifters... there is an empty lifter measurement at the valve tip to get the preload right before initial start up.... it is like 0.070" with the individual cam lobes on the base circle and the plunger bottomed out by rocking the rocker arm..

i know that there is a lot more... including pictures.. but its too hot to search for them....

butch27 · July 19, 2009, 11:12:01 PM

I have found no torque specs, just says tighten until you can barely spin pushrod then turn 1/2 turn more. Just what kind of lock nuts are they suppose to have? Mine look like hardened regular nuts.

wayne petty · July 20, 2009, 12:09:05 AM

which type or rocker are studs do you have?

?

3/8" shank with a 3/8 thread .,,, one size from bottom to top...

3/8" shank necked down to 5/16 threads.

??/

OR... but it sounds like you have studs... bolts through the rocker arms..

wayne petty · July 20, 2009, 12:26:34 AM

in the paw catalog... there is a comp cams part number comp-4610-16 rocker arm adjusting kit for sb ford w/non adjustable rockers...

it looks like in the description.. a spacer for each stud to fit over the pivot ball and a new nut that is a locking nut...

take a 3/8" open end wrench... place it over the threads on the rocker arm studs... if the open end fits tight... you have adjustable valve train... and your nuts are worn as they are able to move without your help.

if the 3/8" open end wrench wobbles on the stud threads... but a 5/16 open wrench is just right... you have non adjustable valve train.. tighten the rockers arm nuts to 18 ft pounds..

butch27 · July 20, 2009, 08:47:12 AM

That's it - my nuts are worn out, ( in more ways than one LOL) Buying all new. Thanks Butch

Learpilot · July 20, 2009, 01:22:36 PM

Quote from: "butch27"That's it - my nuts are worn out, ( in more ways than one LOL) Buying all new. Thanks Butch

A cheap way to make the nuts stay tight is to turn the flat on its side and hit it with a 2 lb hammer. That will make the nut smaller and will stay tight. I had a simular problem with my son's Chevy Truck 250 engine.
I thought that the studs were coming out, but were not. The threads were just a little smaller. The whack with a hammer did the trick !
Rick

chimp koose · July 20, 2009, 07:56:16 PM

you could also use longer rocker nuts with the allen head set screws in them . Adjust them how you want ,then tighten the set screw,they stay locked. I think a number of companies make them.

butch27 · July 20, 2009, 08:04:07 PM

The nuts I've bought do NOT look like lock nuts. I re adjusted the valves and 20 min. later they backed off.What the heck? The NAPA book says these are the correct ones.

reborn55 · July 20, 2009, 09:04:36 PM

Had a similar problem on a pontiac years ago nuts were on upside down. Sure yours aren't--Is there enough room to double nut them

wayne petty · July 21, 2009, 02:20:51 AM

what part number nuts did you get?

?/

what size socket did you use on them?

?/

a simple answer ...

single size stud or necked down?

?

valves keep backing off

Learpilot