MTFCA Forum

Just pulled the head on my speedster. 30+ years since it ran. Wanted to see if I could 'unstick' a valve. No ridge, domed pistons, number two has negligible movement. Went to check number one and it dropped about 1/4". Do you think this is too much to take up with removing shims? If it even has any. Regardless, I got the valve to start moving again.

Yes, to much for any shim adjustment, if you get it running be prepared to catch that rod out the side of the block.

If you have 1/4" slack in a rod bearing, you probably need a crank and a rod. I'd expect the piston to be cracked or otherwise damaged, too. Is there any evidence of the piston hitting the head? Maybe someone loosened the rod cap for some reason and did not reassemble it. Broken crank?

Piston seems to ride fine inthe bore. When my father inlaw first bought it, it had a knock, but it was assumed that it was the water pump hammering. I'll need to pull the inspection cover to see what's up.

Petrah Phyre wrote: ↑

Sun Feb 13, 2022 5:12 pm

Piston seems to ride fine inthe bore. When my father inlaw first bought it, it had a knock, but it was assumed that it was the water pump hammering. I'll need to pull the inspection cover to see what's up.

Water pumps typically would not hammer. But then, I've not seen every Model T water pump...

The pump was jumping forward on the belt. When we held it back with a 2x4 the knocking drastically decreased. I have pulled the pump and do not see any sign of impact inside. I will be removing the inspection cover and see what I have to work with.

If I understand you correctly, one of your pistons can move up and down about 1/4" in the bore without the rest of the engine moving. Is that correct? (Have you tried rotating the crankshaft pulley back and forth by hand to see if it can move independently of the rest of the engine?)

When using the hand crank, the crank throw (sic) will pass TDC and the piston will start down with it. At that point, the piston can be pushed down to meet the crank. Either I have a very worn journal or I have a loose/worn rod.

Not good. Most likely, the crankpin is hammered flat, and the rod and piston are ruined. The engine and transmission probably have a good bit of metal flakes and particles in them. When you take the plate off the crankcase, look for metal debris in the troughs. If it's present there, it will be present throughout the engine/transmission. That's the likely scenario, but you may be lucky. Perhaps the rod cap nuts came loose, and the engine was not run long enough to do serious damage. I'd think the piston would have been hitting the head. Whether it did or not, the hammering of the loose rod most likely damaged it. If it isn't cracked, it may be about to.

I agree that there should be signs of piston/head contact. I do not remember seeing any though. I will check the next time I am out there. I do know that my father in-law was upset with the knock because he was sold this car with a "fresh rebuild", so it may not have been run very long. The lack of carbon on the piston tops makes me hopeful. Was hoping to get it moving for a quick jaunt to my brother in-law's so he could see his Dad's car running before we move. May be too many things that need to happen to meet that goal. With a 30 year parked time, I may be in dangerous waters without a complete run through. dauntless geaser here i come.

1/4 " is about as much as a complete loss of babbit.
Unless there was no friction (like no rings) Why would the piston tend to over travel into the head?
Open it up & look. That will end the conjecture.

At higher speeds, I'd expect inertia to overcome ring friction and compression, especially at higher speeds and closed throttle.

TXGOAT2 wrote: ↑

Mon Feb 14, 2022 2:13 pm

At higher speeds, I'd expect inertia to overcome ring friction and compression, especially at higher speeds and closed throttle.

That could be, if there is less than 1/8" piston/head clearance.. (net extra travel)
This motor should have been shut down pretty fast. All hell was breaking loose under the hood. Who keeps running? Hopefully thats the case & there is minimal damage other than the need for 1 rod.

The bearing may have been too tight, and caused the babbit to "smear" and destroy the oil clearance. Heat would build up quickly at that point and a thick-lined rod could get very loose in a hurry. If the rod and crankpin aren't severely damaged, most metal residue in the engine would be babbit, which is not nearly as damaging to the rest of the engine as would be particles and flakes of steel from the crank and rod. Babbit residue would not be attracted to a magnet, and is usually soft, grayish flakes, tiny blobs, broken bearing fragments, or a sort of gray paste. Steel residue can be be powderlike and may be shiny, sharp flakes or blueish flakes.

Sean,
Have you checked the gudgeon pin ( sorry wrong english language ) wrist pin, I have seen some realy worn out pistons before?
Craig.

Craig, thanks for the vocabulary lesson. Not sure if I have heard it called that. I have not, as of yet pulled the piston to inspect. I will make sure to post some pics once I have the chance.

Measured the piston drop and it ended up being 0.10". Drained the oil/water/babbitt sludge. Pulled the inspection cover. Noticed right away, the side babbitt was peeling and all of the shims were on one side. I assumed you would balance them. Pulled the piston and as you can see, the babbitt looks to be a bad pour. Leary about the rest of the block. I checked and I have a full set of rods with fresh babbitt that look to be in good shape. Checked the wrist pin and it is loose as well. I know I have a set of new domed pistons somewhere, I'll just have to dig them out to see what I have. May just need to button it all back up until after our move to SD.

Looks like mostly babbit damage. That's way better than steel on steel.