I have less than 300 miles on a rebuilt 272. (55 Ford Country Sedan wagon) I took it out last Sunday. Everything seemed fine until I ran her up to about 55mph on the freeway. (I've driven it on the freeway before) All of a sudden, I heard this knocking and stuttering as if one of the sparkplug wires came off. I immediately got off and nursed it back to my garage, experiencing this problem all the way. I could feel thumping coming up through the carb. It increased with the speed.The wires were all on. A friend thought it might be a stuck valve. I shudder to think it's anything serious. Any thoughts? I'm not really a mechanic, but I know which end of a wrench to use.

"You can lead a horse to water...but a pencil must be lead."

 

Cleveland, Ohio

Maybe a bent/broken push rod. Can ya tell which side it is on? Pull the valve cover to see how they look... The old push rods tend to bend easily.

BOB

I'm a new guy. I just did the same thing on my 55 Customline. It has the original 272 in it. I sounded like a broken crank and you could feel it through the floor. I pulled the V/C and a pushrod had bent and fallen in to the motor. I fished it out with a magnet. I had some used ones in the barn, so I cleaned one up and put it back in. I backed the locknut off, counting the # of turns so I could put it back in the same spot. I also tied a piece of cord to it, in case it fell in again. I started it again and the noise was gone, but the valve wasn't moving. I moved the rocker arm over and tapped the valve with a rubber mallet a few times and it started moving. I also poured some Marvel Mystery Oil in the head around everything and put the V/C back on. I let it run for a while and it sounds fine. I went around and listened to the exhaust and there was no miss at all. Love that Y-block sound! Glad I found your site and others who share the love for these motors.

I reckon you can do all you say,but first you gotta catch me........If you can.   Luke Doolin-Thunder Road

Sounds like a bent or missing pushrod as mentioned.  Sometimes with a new engine a valve will stick for a moment and that is all it takes for the pushrod to bend or just drop out.  If you are lucky the valve will pop back and did not bend from contact with the piston.  Be careful of old gas in the tank that is good for hanging a valve for a second.

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

The use of old fuel on a fresh rebuild is an ongoing problem.  An engine will usually fire up okay on old fuel but will leave a varnish film on the valve stems/guides which increases the opportunity for the valves to stick and raise havoc with the pushrods.  My recommendation is for any fuel that’s over 3 months old to be drained completely from the system and replaced with fresh fuel.

Lorena, Texas (South of Waco)

Ted , does that go for winter stored vehicles that sit for up to 5 months ? I top off the tank and add 4 oz of marvel mystery oil to it .  Seems to work ok

Marvel Mystery Oil is not a ‘life extender’ for fuel but definitely nothing wrong with having it in the fuel anyhow.

 

Warmer temperatures speeds up the degradation process of the gasoline.  Having partial tanks of fuel also speeds up this process as once fuel starts to degradate, the oxidized fuel basically seeds upon itself for faster deterioration.  The additives (shelf life extenders) that use to be put in the fuel to prolong its life have been reduced to the point that fuel no longer holds up for extended periods like it did in the Sixties.

 

With all that said, winter temperatures and a full tank of fuel slows down the degradation process.  But additives like Stabil will allow fuel to sit for longer periods of time without the fuel deteriorating as quickly.  For myself, I’ll use premium fuel and keep the tanks low so the fuel can be used up quicker for those vehicles I don’t drive alot.  The brand of fuel is obviously also going to be a player so I’m sticking with the 3 month rule.

Lorena, Texas (South of Waco)