Tight engine UPDATE #2: 7/8/15
 

See post #24 on page 2 for most recent update.

OK, I thought it was a ring gap problem, but now I don't think so, but I am lost for options. Here is the earlier thread for background:
https://fordbarn.com/forum/showthread...=170253&page=2

I set the rings all to mfg's specs, and rechecked the clearances of the pistons and rod bearings. I changed out the starter for one I knew was strong, and the battery is only six months old and has a full charge. I finished reassembly yesterday and went for a ten mile drive today. When I stopped, the engine would not turn over. I waited about four minutes, then it would turn very reluctantly, enough to get started and head home.

When I got home I shut it down, and immediately tried to start it. It would not turn over. I tried by hand, and I could turn it partially, about 1/4 turn, with the crank, then no more, but I’m a weak old guy. Then I removed one spark plug, #2, just to see what that would do. It turned over with the starter!

At no point on the drive did the engine indicate overheating according to the motometer. The radiator doesn’t feel overly heated in comparison to my other A’s. Perhaps removing the plug relieved the compression, allowing it to turn? This might also happen (release of compression) by waiting five or ten minutes.

I am pretty sure at this point it is not something that is too tight, but perhaps something that just needs more breaking in. That may be wishful thinking, but I’m gonna go with it, and drive it, unless someone comes up with a theory about what the hay is going on here.

Re: Tight engine UPDATE
 

Well that's an odd one for sure...too much compression seems an unlikely problem for a Model A engine but that is how it appears...

Someone told me once that when shut off an engine will probably stop turning when it comes up against the cylinder with the most compression....maybe #2 in your case....

See if it does the same thing next time if you loosen #2 spark plug....

Re: Tight engine UPDATE
 

My engine when newly rebuilt was real tight and I would start it and drive around the block and then let it cool down and did this about 5-6 times before I ever took it out for a short drive. It took a while to fully break in. keep changing the speed and don't let it lug or over-rev. Remember that a hot starter needs more battery getting to it to do its job. Do you have double aught (00) cable to the starter? that is the best to get the starter revving!

Re: Tight engine UPDATE
 

30 minutes after my previous post, the car now turns over normally and starts just fine.

Re: Tight engine UPDATE
 

I got this story second hand so I do not have all the details.

As I remember it happened sometime ago with a California builder.

1. Recently rebuilt engine was stopping when it warmed up and would not turn over until it cooled.

2. The engine was returned to the rebuilder.

3. The response was that the pistons were expanding and stopping the engine from turning until it cooled off.

4. The builder said that he had bought a large number of these pistons and that the pistons were made from a defective alloy and that they expanded too fast and too much compared to normal pistons so they got stuck in the bores.

It might be something to consider in this problem.

Maybe there are still some of these pistons being sold at flea markets.

Re: Tight engine UPDATE
 

Benson has an interesting point as it could be defective pistons or if cylinder sleeves were made of similar metal, there may be binding. However, would that allow the starter to turn over the engine once he removes the spark plug on cylinder 2?
Could there be anything causing binding of valves with the spark plugs?

Re: Tight engine UPDATE
 

When disassembled, there was no indication of the pistons coming into contact with the cylinders during operation. No scuffing or scarring on pistons or cylinder walls. If there was expansion during operation, it should show up then (stop running?), not only when the engine is shut down, no?

Re: Tight engine UPDATE
 

I bet you have a loose connection between the battery and the starter, or battery to ground, or the 12 volt cable, as 1930 said.

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You need to have the starter checked for overheating. It sounds like the motor is fine but the starter is getting hot and failing.

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I'm thinking the same thing, bad/weak ground ,corroded or too small cables, or a starter problem. New doesn't always mean it's good(unfortunately)! I'm curious to hear the results from post 8.

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1. When the engine will not turnover with starter, can you turn it with a hand crank?

I am thinking that if you can turn by hand then it might be a hot starter issue.

Re: Tight engine UPDATE
 

Removing #2 spark plug may be misleading. By the time you did other checks and got the plug out, the engine may have cooled down enough to turn over anyway.

Re: Tight engine UPDATE
 

First thing I thought was starter. It might have had enough power to turn over the old engine with poor compression, but now it is too weak. Check grounds, contacts, brushes, commutator, bearings or swap a known good starter and see if the problem goes away.

Re: Tight engine UPDATE
 

Good suggestions, gentlemen.
30 coupe: it rocks back when cold. I haven't tried that when it is warmed up.
Jackson: all connections have ben cleaned and tightened. Cable may be bad. I'll check that.
James: I have replaced the starter with a known good one.
Benson: I can turn it about 1/2 turn.
40: there was less than minute between shutdown and plug removal.
Pat: see answer to James above.

I won't be able to work on it again till about Friday. I'll update then.

Re: Tight engine UPDATE
 

1/2 a turn ... OK.

1. An out of round bearing journal with tight clearance would do that ... But would not expect to see that on a fresh rebuild!

2. Cylinder bore taper (sleeve problem) as mentioned above with pistons/rings binding up ... but again as in #1 not likely.

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When engine stops the temperature in block goes up for a period of time when the water stops circulating.

Not sure how much the temperature would have to up to cause this problem or how long it would take.

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I think you have checked everything that could reasonably be checked, but I could be wrong.
If it were me, I'd change the oil, keep a good eye on the water and the oil and run it, it'll wear in.:)
Good Luck!

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I agree and woudl do as Mr. Lott suggested. I believeit just need to "wear in" - no mas.

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Is it normal for a fresh engine to have to 'wear in' before it quits seizing when warmed up?? NO! Something is definitely out of the ordinary here that normal measurements are not picking up. I still think it has to do with the sleeves. Benson's comments about the brief temperature rise upon shutdown (or idling after a good run) may be a clue. If a sleeve is a little too tight and under stress, that little extra expansion from heat might just be enough to pinch the piston until it cools back down. This happens quickly, so the oil film is not wiped off before it stops.

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I don't hear you complaining about heat, so I am with Mr. Lott. I believe you have a good engine, but you should check that rock back trick when the engine is hot (great trick 1930 coupe) I would keep an eye on the oil and the temp and look for other causes for your trouble. I would also add a ground strap between the frame and the engine/tranny. I'm thinking that after a new rebuild you will hear and feel lots of things that spell disaster but are nothing more than new a engine sounding and feeling different than your old engine. please keep us posted.

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40: I keep coming back to piston clearance, though it seems from all I now know about the honing and setup and what I have personally measured that it should be within tolerances. Piston mfgr says.003; I measured .004+. Others have said with new aluminum solid skirt pistons it should be .0045+. This seem so miniscule as to hardly result in the condition I am experiencing. But I just honestly don't know.

And on top of all that, the bendix spring on the "I know it's a good one" starter I just installed broke! Close inspection showed the spring was cracked beforehand, and I'll install the new one tomorrow. Sheesh! I expect I'll be tearing the engine down again in the not-to-distant future!

Re: Tight engine UPDATE
 

My money would still be on ring end gap.

Re: Tight engine UPDATE #2: 7/8/15
 

Just to do a followup to my followup, I reassembled my engine, changing only the torque on my rod bearings to 40# ±. The ring gaps and piston clearances, as I mentioned earlier, were all where they should be by your suggestions and the mfg’s specs. The main bearings were set by the rebuilder, Bill Barlow, who absolutely knows his stuff (past MAFCA tech director, Model A engine rebuilder for over 30 years), so that left only the possibility of too tight rod bearings. The result is the engine now no longer seizes up at shut down when driven fully warmed up. It’s still tight, but no more than I am used to from previous new engines.

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Didn't Henry run his engines on a stand for some time before installing them? I remember seeing the massive cooling system next to the engine stands.

He knew when to stop the break in in when certain gauges read lower readings.

Larry

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After reading about all the possibilities I'll share my experience with a weak starter. Took it apart and the comm., brushes, field resistance, bearings, armature wasn't dragging on the field poles, all looked good. Measured the volts again on the starter switch and it was OK but I was completely overlooking that switch on top of the starter. So took it apart and found a defect in the insulating paper that allowed part of the current to bleed to ground. Replaced the sw. with a spare and the problem was fixed.

Peteva.

Re: Tight engine UPDATE
 

What were you torque did you have on the rod nuts before?

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Sorry, what did you torque the rods nuts to before 40 lbs?

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Can't remember for certain, but I think it was 60-65#.

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Rod bolt torque (or main bolt torque) should have nothing to do with clearence. Clearance is adjusted by shims not bolt torque.

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I'm sorry that is just wrong. The correct fit is where the crank is of diameter x and the hole in the big end is of diameter x plus however many thou clearance you need. If you try to adjust the clearance with shims you can no longer have a round hole in you rod but an oval one where the correct clearance is only across the minor diameter of the oval.

The correct torque for the nuts / bolts is one that is tight enough to stop any movement between cap and rod without exceeding the load capacity of the nuts / bolts. This is much better done by measuring stretch in the studs rather than torque and that is what is more commonly done on modern engines. Ford owners are lucky as there is a ton of data. With a lot of low volume vintage engines all of this has to be calculated from scratch.

If you have strong enough nuts / studs then with some cap designs it is quite possible to torque them to a point where the cap will start to deform and this will cause binding of the crank.

The best shops and engine builders often line bore main bearings and big end journals with the caps in place and torqued / Stretched to final values. I have known vintage engines where the crankcase moves when the mains are fully torqued up. When machined as above the crank initially feels tight on installation but is perfect with everything done up tight !

Re: Tight engine UPDATE
 

I replaced the starter with one that performed properly from another car. That did not solve my problem.