93fordf150

Hello all , I have a 93 f150 300 six , I have this problem with some of my rockers coming off my push rods , This started last year when found #6 cylinder exhaust valve push rod off the lifter , I replace all 12 with new rockers and lifters , Motor ran fine until a few weeks ago when something happen again , When I pulled the cover off I found three bent push rods and one had come off again ,So I went out and change all push rods stated it up I think one fell off again , One of things I have notice is when I Torque down the rockers the bolt gets tight right at the setting, Hope some can point me somewhere , Not sure on miles I think the motor is not original because I cannot fine tag on block , Speedo was at 279,000 plus the last time I could read it and that was a while ago , The motor was running strong does not burn oil which is why I think it is not original motor , Thanks.

Steve83

It's caused by ethanol in the gas, which causes the valves to stick. Put MMO (or some lead substitute additive) in the tanks, and shop for low-/zero-ethanol gas stations. The phone app is "PureGas" or something similar.

There is no "setting" for the rockers on these smallblock Ford engines - they're tightened all the way down to the specified torque. The lifters (HLAs) maintain the valve adjustment (until the valves stick).

My 4.9L has over 860Kmi (yes, closing in on a million) without rebuild, and still runs like-new. It's not the original, though - I put most of those miles on it in the previous chassis, after getting the engine from a junkyard.

93fordf150

Thanks for the reply , At this point I'm not sure on what to do , I had put all of the new push rods in when to start it up , And still the same thing , From what you are saying is making me think that some of the valves are stuck if so what can I do to free them up so the motor will run for the gas will do it's job to keep them from sticking , Thanks John.

RLXXI

The only true fix is to remove the head and take it to a machine shop for repair.
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93fordf150

Well I figured that's what someone would say , Well thanks for getting back to me ,Looks like I get my hands dirty .

Steve83

Penetrating oil, or a strong solvent like original Goof Off or Berryman's B12 Chemtool might soften the varnish enough for the engine to run well enough for the top-end lube to work. I'd try one or all of them before tearing the head off. You can't really do any more damage - you just might bend another pushrod or 3.

midwestbird

this is an old thread, I know, but I'm having a similar issue with my 1990 4.9L. Did you ever figure out the cause or solution?