The Ford Barn

700rpm · 06-16-2015, 07:42 PM

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!

katy · 06-17-2015, 10:18 AM

My money would still be on ring end gap.

700rpm · 07-08-2015, 04:07 PM

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.

Larry Jenkins · 07-08-2015, 04:28 PM

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

Peteva · 07-08-2015, 04:53 PM

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.

goodoldvic · 07-08-2015, 05:14 PM

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

goodoldvic · 07-08-2015, 05:16 PM

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

700rpm · 07-08-2015, 07:42 PM

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

aermotor · 07-08-2015, 08:25 PM

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

Mike Crehan · 07-08-2015, 10:25 PM

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 !

700rpm · 07-08-2015, 11:56 PM

Quote:

Originally Posted by Peteva

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.

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

06-16-2015, 07:42 PM	#21
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 6,039	Re: 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! __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole. Last edited by 700rpm; 06-17-2015 at 11:00 AM.

06-17-2015, 10:18 AM	#22
katy Senior Member Join Date: Jun 2015 Location: Red Deer, Alberta Posts: 6,077	Re: Tight engine UPDATE My money would still be on ring end gap. __________________ If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn!

07-08-2015, 04:07 PM	#23
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 6,039	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. __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

07-08-2015, 04:28 PM	#24
Larry Jenkins BANNED Join Date: Feb 2015 Location: East Central Iowa Posts: 1,275	Re: Tight engine UPDATE 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

07-08-2015, 04:53 PM	#25
Peteva Junior Member Join Date: May 2010 Posts: 28	Re: Tight engine UPDATE 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.

07-08-2015, 05:14 PM	#26
goodoldvic Senior Member Join Date: Sep 2012 Location: New Jersey shore Posts: 274	Re: Tight engine UPDATE Sponsored Links (Register now to hide all advertisements) What were you torque did you have on the rod nuts before?

07-08-2015, 05:16 PM	#27
goodoldvic Senior Member Join Date: Sep 2012 Location: New Jersey shore Posts: 274	Re: Tight engine UPDATE Sorry, what did you torque the rods nuts to before 40 lbs?

07-08-2015, 07:42 PM	#28
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 6,039	Re: Tight engine UPDATE Can't remember for certain, but I think it was 60-65#. __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

07-08-2015, 08:25 PM	#29
aermotor Senior Member Join Date: Mar 2015 Location: Greenville, SC Posts: 1,099	Re: Tight engine UPDATE Rod bolt torque (or main bolt torque) should have nothing to do with clearence. Clearance is adjusted by shims not bolt torque.

07-08-2015, 10:25 PM	#30
Mike Crehan Member Join Date: Jun 2012 Location: New Zealand Posts: 45	Re: Tight engine UPDATE 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 ! Last edited by Mike Crehan; 07-08-2015 at 11:02 PM.