Rebuilt Engine: How tight?

[Brobrian]

Pops brought a "newly rebuilt" engine down on his last visit. It had been setting in his shop for about 20 years, but the babbet bearing were newly poured and bored. Completely gone through It was pretty tough to turn over, so we pulled the head and pan. It was immaculate inside! We put some oil on the journals and in the cylinders and it seemed to loosen up some. We were turning it over with a 16" pry bar.

Dad wasn't too concerned, however. He says Grand dad used to rebuild them and then pull the car around behind a tractor for about a half a mile to get the oil up into the proper places, then throw some plugs in it and pull-start it with the tractor. But then Grand dad used a soup can and emery cloth as a cylinder hone.

I plan to put this motor, which originally came form Grand dad's combine harvester in my pickup this summer. I've considered making a test stand for it, but that seems like a lot of extra work and precaution.

What are your thoughts, gentlemen?

[CarlG]

I've heard that the combine engine mounts make nifty run-in stands.

[BILL WILLIAMSON]

Shucks, with all the time it would take to build a test stand, you could have it in the car & a couple of hundred miles on it!
Bill W.

[wrndln]

I think you would be OK with it being pretty tight. If you can turn it over with a 16" bar, it is probably OK. The last engine I put together was quite hard to turn over because I wanted the rods and mains fairly tight so I didn't have to readjust them very soon. It started fine and runs good.
Rusty Nelson

[glenn in camino]

If the starter motor will turn it over and it starts, It's not too tight.

[Lee Mitch]

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That sounds very similar to the one I had restored. I had to use a 1/2" drive breaker bar to turn it over. I bent and ruined the type that you can you use with the radiator in place. I could not use the original hand starter bar either. One other thing is that a modern bendix would not work, so I put the original back on and it worked fine. Once I started it and ran it for a couple hours I placed the modern bendix starter back on it. I have very few miles on it still, but have had no problems.

[CarlG]

I use a 1/2" breaker bar or a long handle ratchet with a socket on the crank nut and an extention coming thru the crank hole.

[31Abone]

I just had one that was pro built by a idiot ..took a 3' bar to turn it ..I took it apart and checked bearing clearance it was zero..shimmed it to 15 thousands ..works good now

[colin1928]

My rule is 30 to 40 max ft/lbs with out spark plugs

[Tom Wesenberg]

My friend's 31 wide bed engine was rebuilt and tight to start turning, even with my KRW flywheel bar. Once the crank was turning it felt OK, and you could stop and start turning it again right away and it felt OK, but let it set for 10 seconds or more and it was tight to get started moving again. It fired up and ran fine and we now have a couple hours of run time on it. Still waiting on his part time painter to finish the box for it. It's only been 11 years now.

[tbirdtbird]

you can get oil to all the place you need by dumping a quart down the dizzy hole and the rest in the regular filler, which can save you pulling the pan and side cover. I have heard of engines being set this tight but i am personally not in favor of it. If you already have the pan and side cover off you can easily check the mains for clearance and adding a shim if needed to get .0015

[Brobrian]

Great, Gentlemen, as always.
Never know how much to trust Pops and his stories about Grand Dad. Looks like they were right on the money this time. Now I'm looking forward to the engine swap. Can't wait to get that thing in the truck.

[Tom Wesenberg]

I would put some oil down each spark plug hole then hand crank iit over a couple times to oil the cylinders and pistons.

[H. L. Chauvin]

Hi Bro,

When you remove all spark plugs & have no crankshaft torque resistance caused by compressed air in the combustion chamber, the crankshaft should turn fairly easily.

With Model A gravity flow oil & a splashed oil systems in Babbitt bearings as opposed to later pressurized oil systems, having too tightly fitted Babbitt bearings can lead to wear in the very near future.

Like that of reply no. 8, I had a guy who said he was an engine rebuilder pour new Babbitt & line bore my A engine years ago who later reported that he "liked" tight Babbitt bearings.

The crankshaft could not easily move sideways a few thousandths of an inch in the mains & the connecting rods could not easily move sideways in the journals -- the crankshaft was very difficult to rotate.

When I got home I removed the pistons & added shims to mains & to the connecting rods such that no up & down play could be felt; however, movement sideways was easy.

Ford repeatedly mentioned this age old proper Babbitt bearing adjustment in his Ford "T" Manuals, & did it back then without measuring Babbitt clearances with Plasti-Gage & aluminum foil; hence, by the time the A came out, all Ford & other vintage mechanics already knew how to properly set Babbitt bearings with shims -- so did all reliable vintage mechanics for other types of internal combustion engines & steam engines.

My same aforementioned Model A engine, (with detergent oil changes every 500 miles), is now 54 years old with Babbitt in great shape.

I really admire your soup can & emery cloth.

[BILL WILLIAMSON]

Vermin's rebuilt engine, with maybe 40 miles on it, has set for 2 years. With plugs in, I couldn't even BUDGE it with the crank. Stepped on the starter & the OPTIMA spun that thing, like, "RRRRRRRRRRRRRRRRRRRRRRRRR-----RRRRRRRRRRRRRRRRR----RRRRRRRRRRRRRRRRRRRR!! BEAUTIFUL SOUND, I almost P**D myself, got to get that trap completed, afore' I get old & die!
Bill W.

[George Miller]

A long stroke engine like a Model A will be harder to turn than a short stroke like a 283 chev. The resistance from the piston is multiplied more on a long stroke. It is all about leverage.

[Sixseven]

Originally Posted by George Miller

A long stroke engine like a Model A will be harder to turn than a short stroke like a 283 chev. The resistance from the piston is multiplied more on a long stroke. It is all about leverage.

I'm confused, I assumed that as long as the piston and rings had contact with the cylinder wall whether traveling in one direction in a long stroke engine or up and down in a short stroke engine, the resistance would be identical.

[Tom Wesenberg]

Originally Posted by Sixseven

I'm confused, I assumed that as long as the piston and rings had contact with the cylinder wall whether traveling in one direction in a long stroke engine or up and down in a short stroke engine, the resistance would be identical.

No, you have to think of the crank throw as a lever. The further out the crank throw is the more leverage you have for the piston drag to hold the crank still. Easiest to picture this when the crank throw is 90* to the piston rod, which is the point of greatest holding power for the piston drag to hold the crank still.

[BILL WILLIAMSON]

On a short stroke engine, the inches of ring travel per revolution are LESS & result in less effort to turn it & also result in LESS ring wear.
Bill W.

[tbirdtbird]

well said