Sticking valves- bent push rods

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May 23, 2009 | 03:29 PM

Jerrybo66

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From: AZ.

Sticking valves- bent push rods

My '73 F-100 has been bending push rods and destroying lifters, four rods, with two lifters. There is about 20,000 miles on a professionally built motor. It always ran great. About 100 miles ago I started it up after sitting over a year. I changed the oil and being these old motors seem to run on anything I just added fresh gas, later filling the tank. I just replaced a rod this morning and almost afraid to fire it up. So far I've been fortunate enough to be able to fish out the lifter. I left the valve cover off after the other replacements and all valves were working. While staring at it today I noticed that the ones that bent were on the intake valves. Is it possible that the old gas even though mixed with fresh, would cause varnish to burn on the valve stems enough to seize them up solid? After moving the rocker I had to drive the valve down with a brass pin & hammer repeatedly until it freed up. What could cause this and what would be a remedy? Would carb cleaner or something else sprayed down the carburetor help, maybe spray, crank without starting and let sit? What about SeaFoam or Chevron Injector Cleaner in the tank?
Thanks for any help.
Jerry..

May 23, 2009 | 04:05 PM

JesusRocks

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Joined: Apr 2006

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From: Waco, Tx

FE's That Bend Push-rods, A Dirty little Secret .: Articles

this should help some. Not sure on the valve sticking others with more info should chime in. Also try posting this in the FE forum. Lots of good guys there with much more knowledge than me. hope it helps

May 23, 2009 | 04:17 PM

73CaliF100

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Joined: Jan 2009

Posts: 134

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From: Nor Cal

I know this video is showing an ATV, but it might be worth checking out Amsoil...looks pretty amazing.

Sticky Valve Fix ATV Small Engine Amsoil Power Foam

AMSOIL - Power Foam Engine Cleaner & Degreaser (APF)

May 23, 2009 | 07:00 PM

Old Rusty Wrench

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Joined: Feb 2009

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From: Seattle & Surprise, AZ

Can someone answer. My son OJ is rebuilbing a 390 that has been had been worked on before. He said that it has adjustments (bolt & lock nut) on the rocker-arms at the valve stem/spring. The heads have been reworked and cleaned. Would the .100 to .200 be used in stead of the push rod selection proccess. Additionally would one still need to loosen the rocker-shaft bolts two turns or can an adjustment be made when torqued to spec. What clearence should be used?

May 23, 2009 | 07:07 PM

Jerrybo66

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From: AZ.

Rusty..
What does your post have to do with my question?

May 23, 2009 | 10:20 PM

mikeo0o0o0

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From: Stanley, VA

I think the clue to your problem is the fact that your engine sat for over a year and that the rods that are bending are intakes. I suspect that moisture has gotten to the intake valves and made them sieze in the valve guide.
You can check fairly simply on which ones are stuck. Pull the rocker arm assemblies off, take a hammer and tap each valve stem. If the valve is siezed you will see a distinct difference. It will have a very solid feel vs. a "hollow" sound.
Depending on how tight they are you may end up pulling the heads.
I've been able in the past to free stuck valves by tapping them and spraying penetrating oil on the stem but this is "iffy" at best (especially if the valve sticks open after you hit it).

May 24, 2009 | 07:47 AM

Tees77f150

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Joined: Nov 2008

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From: Halifx Pa

Quote:

Originally Posted by mikeo0o0o0

This is what I did with my 77 300 I6 which had been setting for close to 20 years. I tapped the valves, which you could feel them when they are loose. I then replaced the bent push rods, and then filled the motor with three qts of 30W, then 2 qts of transmission oil, (Marvel mystery oil will work too. )

This seemed to have work all the stickey valve issues out, and I am not bending rods, which cause the rocker arms to fall off of the rod, then it misses. I was told to drive it for 500 miles, but I am not registered for the road yet, but I let it run for about an hours or so off, and on, and I would drive it across a big field several time. It seems to have worked, and is a non issue for me, give it a try. My stuck valve were intake as well, hope this helps!