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351C Pushrod ate into rocker arms.... OT

A

Aaron Ford

Well-known Member
I have a low mile (44K) 351 Cleveland.
The heads were refurbished by the
previous owner 2K mikes ago. It
developed a tick and upon disassembly I
found the pushed has eaten into the
rocker arm. I switched the number 5
intake and exhaust and the problem
moved so I am pretty sure I am on
track. What would cause this?

To keep this on topic, the 1971 Cougar
convertible is parked where my 1959
Massey 65 used to be...

Thanks in advance,
Aaron
 
A rocker and a pushrod should be CHEAP. Replace them and likely all will be well.
 
The rockers oil through the push rods. Possibly the push rod was clogged, or it may have just happened.

Once the new rod and rocker are installed, start it up with the covers off and be sure all are oiling. If in doubt, pull all the push rods and be sure they are clear. A clogged lifter, worn cam/lifter can also cause oil to not be supplied to the rockers.

The early 351c also used oil deflector clips to help direct oil to the rocker pivots. Are they in place?
oil deflector clips
 
I've also got a '71 Cougar with the 351C. Mine has about 70K miles.
Yea, replace the push rod and rocker arm. I'd probably also replace the lifter there too and add lots of assembly lube to it. The intake manifold isn't too hard to pull on a 351C. It's possible that the push rod became plugged up with dirt or sludge and wasn't sending oil up to the rocker arm.
OR....it may have just wore out.
 
If it was an exhaust rocker that failed, swap an already broken in intake rocker and pushrod to the exhaust and put new parts on the intake. The exhaust rockers run hotter due to heat transfer from the exhaust valve and are more prone to fail. As another said, use cam assembly lube on the rocker and pushrod. When disassembling, always keep pushrod, rocker and rocker sled together so they don't have to break in a second time. Also an oil with as much ZDDP as possible to lube the valve train. A good diesel oil or race oil with high ZDDP content, not any of the SM / SN rated stuff.
 
I now have a new rocker and pushrod on the way. It was #5 exhaust. The rocker arm deflectors are in place. Plans are to put the new parts on number 5 intake and move the existing intake pieces to the exhaust. I suspect modern oil has been used. Maybe convert it over to amzoil Z-Rod?
 
"The exhaust rockers run hotter due to heat transfer from the exhaust valve and are more prone to fail."

That is one factor, but the exhaust valve is also many times harder to crack open because of the residual combustion pressure holding it closed. It amazes me that rockers, pushrods, springs... Anything that takes the repeated beating of the valve train holds up as well as they do!
 

I had a issue like that one time but it would get the rocker in about 300 miles. It was after a rebuild I ended up replacing all the lifters and the issue never came back.

Lack of Lubrication is the issue if its the oil why did it not ware them all out. One thing I know oil may not be needed to lube the valve stem but its needed to cool the valve stem.

I would replace the rocker assy and push rod if the problem comes back go after the lifters.
 
The owner of machine shop I use said that all engines that do not have roller rockers need to have zinc in the oil for lubrication. Modern oils have reduced amounts of zinc because it affects the catalytic converter's. If you can find oil that's listed for off-road use only or racing oil, it will have added zinc. Here's a link:

http://www.amsoil.com/newsstand/classic-and-vintage/articles/flat-tappet-cams-in-classic-cars/
 
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