Tight engine UPDATE

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!
 
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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.
 
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
 
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.
 
Rod bolt torque (or main bolt torque) should have nothing to do with clearence. Clearance is adjusted by shims not bolt torque.
 
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 !
 
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Peteva said:
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.
Click to expand...

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