off Centered Rockers? One slipped - HELP?

[karlatteberry]

After having my heads ported and switching out to 3/8" push rods and new roller rockers I had one of the rockers come off the valve (doing about 90+ mph) while driving down the freeway. I will take you back a bit. Had the heads ported, and machined with new valves, springs, cam (for Pulling - RV), lifters, roller rockers, and push rods. After the first put together, one of the exhaust valves stuck and hit the piston - which of course bent the valve and left me zero compression in that cylinder (no 2). I sent both heads back and the shop worked with me admitting the exhaust seats were just too tight for comfort, so they were redone. Flash forward to Monday, taking my daughter down to college, rocker came un-seated. I will post some pictures, but you can tell on at least 2 of the exhaust valves, that the roller isn't even on the valve stem, but almost on the shoulder. you can also see in the pushrod guide that it has worn quite a bit thereby far enough on cylinder 7 exh that it came off the valve, My question is - what could cause this? the geometry just doesn't seem right if that happens? We did increase the pushrod length slightly to 8.75", but after they were installed, looked like they were riding perfectly centered on the valve stem. I am wondering if the valve seats are still too tight? and it caused lateral force between the roller rocker and the pushrod?

Any insight would be GREATLY appreciated.!!

Engine is a 429

[dbarker]

ought not be doing 90.... good luck with the repairs

[karlatteberry]

I don't think going 90 had anything to do with the breakdown. It was only a matter of time before that came off with the worn guide. That and the rpm's weren't that bad at all as I have pretty tall gears - wasn't over 3000 rpm, of which I go over all the time in 2nd and 3rd gear. Engine should easily do 5000 rpm with what I've done do it.

[tnlprt]

Those are called pushrod guide plates not valve guides

http://www.460ford.com/forum/archive/in ... 45360.html

[karlatteberry]

Thanks tnlprt - I knew that they are called pushrod guide plates - not sure why I put it in that way - oh well......and thanks btw that reference gives great information! I will pass it on to my machinist and get his take on it too.

[tnlprt]

I talked to my machinist today and he said you might need to


cut the guide plate
center the pushrod and rocker
weld the guide plate back together

[chad67]

Are the pushrods bent? I would think that kind of pressure on the guideplate would cause or be caused by a bent pushrod. Are you running hardened pushrods? They may be deflecting under pressure. I assume you replaced them after the first problem with the valves? I know the rockers may have been centered in the closed position, but where were they in the open position? The compound valve angles on the 429 may be causing alignment issues as the valves open.

[karlatteberry]

The push rods are not bent, but when looking I found it interesting that the rockers are 1.73 ratio and 7/16", and my pushrods are 3/8" diameter. Shouldn't they be the same? In reading that article from the 360 forum, I am pretty convinced it is definitely a geometry issue. Anyone have any thoughts on the difference in my rocker from pushrod size indication? could it just be that causing the issue?

[tnlprt]

1.73 is the correct ratio for a 429/460 rocker


Check the end of the push rod and see how it fits the rocker arm....The push rods should neck down at the end

[chad67]

When the rockers are marked 7/16, that should mean the rocker stud diameter, not the pushrods. Something is causing the pushrods to put pressure on the guideplates. If the geometry is correct, there should not be a large amount of pressure on the guideplate, just enough to keep everything in alignment.

[karlatteberry]

Just talked with my builder yesterday and there are two issues. One was the valve stem was .006 over (I believe) on the exhaust. In addition, the lower part of the valve was tapered and causing it to "stick" causing undue pressure on the rockers and pushrods which is what made them "walk". The other issue was that the contact surface for the valve to the head was WAY to small and could not effectively transfer the heat. So between the sticking and over heating (expansion) is what apparently made the pushrods wear against the guide plates.

Thankfully, the guy I go to is totally stand up. He owned up to it and is taking care of everything (even though it was his machinist that dropped the ball here). They are putting in all new valves, valve guides, guide plates, etc. Now all I have to do is put it all back together again....

[Ranchero50]

Yep, makes sense.

I don't have any experience with the 429 family but usually when I'd see wear patterns like that there was a binding issue (either dynamic or static) causing the push rods to deflect and wear. You should see what happens when you use standard push rods with hardened guides... We call stuff like that "Inline machining".

Good luck with the re-rebuild.

[karlatteberry]

Thanks Ranchero50! I really do have a good guy doing this for me. He is going to provide a whole new gasket set as well - which is nice, because they aren't cheap! I like your comment "in line machining" cracks me up.... Yea - they are robust push rods that I have now.

hoping to have the heads back sometime later next week.