Intake valve sticks intermittently...

[Special Coupe Frank]

Periodically, one of the intake valves on my un-restored, 80,000-mile '28 will stick open.

Usually this happens when running at fairly high speed (50 mph), on a long pull: all of a sudden, the valve sticks-open, and if I don't back-off the accelerator, it will start popping-back through the carb.

If I limp over to the shoulder, and let the engine run at a fast idle, eventually( 2 - 5 minutes) the valve un-sticks, and the engine runs "normally", and I go on my way.

This only seems to happen with high-speed running; never when chugging around town at 35-45 mph.

I usually run about 4 oz MMO to each tank of gas.

Next time it happens, I 'm going to try to determine which cylinder is affected, by shorting plugs.

Is this gunky valve-stems, weak springs, combination ?

Any magic elixirs that might help clear it up ?

[Farrell In Vancouver]

Try and Identify which valve then look for a burr or a tight guide. Seems it only happening when she get hot so something is tightening up the clearance and causing it to stick open. Are these original valve springs Frank? Most have had the bun after 80 years and 80 thousand.

[Special Coupe Frank]

Farrell,

As far as I know, the valve, springs, and pistons are all original. The Pistons and Exhaust valves have Ford script on them.

The head has been off the engine before, recently enough that it had a Fel-Pro copper R-3 gasket in it.

While I had the head off to replace the blown gasket, I did note that when any given valve was open, it was not difficult to twist the valve head back and forth with my thumb & two fingers... didn't seem like the valves were under much tension.

Is it possible to replace valve-springs w/o pulling the head ?


SC Frank

[Mitch//pa]

i can wiggle my valves real easy also and seems like very little spring tension. are you sure your chasing the right thing? i have had bad condensors and even fuel trouble make it backfire through the carb.

[ford1]

ive had that happen too, i started running mmo in my oil and a can of stp, it helped it hasnt stuck a valve in over 6 months, might be worth your time to give it a try

[Logan]

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Originally Posted by Special Coupe Frank

Farrell,

As far as I know, the valve, springs, and pistons are all original. The Pistons and Exhaust valves have Ford script on them.

The head has been off the engine before, recently enough that it had a Fel-Pro copper R-3 gasket in it.

While I had the head off to replace the blown gasket, I did note that when any given valve was open, it was not difficult to twist the valve head back and forth with my thumb & two fingers... didn't seem like the valves were under much tension.

Is it possible to replace valve-springs w/o pulling the head ?


SC Frank

Yes you can. You just have to get a valve spring compressing tool, and remove the manifolds. But after you compress the spring to take out the keeper, and you are going to take out/put in he new springs you have to stick one finger through the Intake/exhaust ports to hold the valve up as far as it can go, so you have enough room to wiggle the springs in and out. Just make sure when its all done you make sure to put the keepers back in, or else you really will have some bad valves fast. This whole prosses wont take more than an hour maybe two depending on how fast you can work.