MTFCA Forum

New rebuilt engine starts & runs good for two or three minutes then it seams to tighten up and the engine slowdown until it dies. It will start right back up and do the same thing. What do you all think.

Jack up the rear wheels and see if it still happens. That’s how I discovered that my bands were out of adjustment, causing things to tighten up.

Could be any of a number of things,
Ring gap, piston clearance, piston pin, cam shaft bearings, the Babbitt on crank, transmission bushing and even the valves or push rods in the guides.

Kerry mentions insufficient piston to cylinder clearance and this is a really common problem. The T engine requires substantially more clearance (.005” works well) than most other engines and if the machine shop is not familiar with T engines then they will usually fit them too tight.
I learned this the hard way many years ago and have honed out other people’s engines over the years

Also could be the engine was put together to tight. Ford would run them in at the factory.
Nowadays some tend to make the tolerances really close in thinking it’s better that way. It would be but to much could lead to issues. Could be some of the areas mentioned earlier.

Les is right on. Also piston pin bushing too tight. The pistons all need to be honed.
Also could be triple gear pin bushings. But they will only bind if you are using low or reverse. Dan

Ron, did you rebuild the engine yourself or have some one do it? If the latter, was it someone experienced with Model T engines?

I freshened up my 11's engine this spring. It was so tight after assembly I had to use a pry bar to turn it over fully assembled with out bands (Don't worry the forth main was in perfect alignment). I used the pry bar and just kept turning it over until gradually it loosened up enough to start it. I did not replace the pistons or pins but just re-ringed and set the crank and rod bearing clearances. After the initial start up it loosened right up, start fine. Les's advice sounds right to me.

Dan.
The only time that triple gears are not turning is when in top direct drive, in neutral they still spin and can stall the engine and or try to drive the car forward if locking up. If the parking brake is working good then it would stall out the engine.

Piston to cylinder or piston pin fits are too tight.

Ok guys thank you for all your ideas. I found that I didn’t have the neutral adjustment bolt tightened down enough to allow it to be all the way into neutral. So I just needed to recheck my work. Thanks

A steel rod turned to .740 and long enough to go through the four rods is an easy check for rod straightness once the rods are fitted to the crank.

I'm having trouble with your problem being solved by adjusting the neutral, although that may have been needed.

Your initial post stated that the engine starts and runs fine for a while, then "tightens up" and slows down and stops. You further stated that "it will start right up again" and repeat the process.

My problem with the idea that this is caused by something heating up and seizing, is that if anything gets that hot, it will surely take a bit of time for it to cool down enough to un-seize. But if it will start right up again after it stops, I don't agree that it's something getting hot and seizing.

My vote is that your problem is poor fuel flow. I'm imagining that the carb runs dry and the engine stops, and as soon as it does the slow fuel flow refills the carb and it will "start right up."

We've often suggested that you get a gallon can and place it under the carb, then open the drain cock on the bottom of the carb and watch the flow of fuel from it. If it can flow at least half a gallon without slowing down, then my guess is wrong. If it tends to slow down to a trickle or less, that's your problem (in my often-wrong opinion). And, it's most likely the mesh strainer in the bulb under the tank, but it could be other things as well.

Best of luck!

Make sure the vent in the gas cap is not plugged. Next time the engine stops after a few minutes running, immediately loosen the gas cap a try to determine if you hear a slight "hiss" from inrush of air which would a slight buildup of vacuum in gas tank.

Ron "it seams to tighten up and the engine slowdown until it dies" Have you confirmed the engine is 'tight'? Immediately after it stalls can you still turn it over with the crank? IMHO, this sounds like fuel starvation, whatever the cause, good luck on the repair, hope it's simple. jb