I'm building my engine up and I ran into a problem with the center main thrust bearing installation. First off all my main bearings are 20 and the thrust bearing is a 10. The crank didn't sit in as easy as I thought it would, but I continued on anyway. Finally I got all the main caps torqued to the right specs. According to the book (after you install the harmonic balancer bolt) the crank should start to move around 10-12 ft lbs of torque. Well my crank won't start to move until about 60 ft lbs of torque.

Is this normal, or was there a mess up in the bearing kit?

Also is it common for machinist to grind the crank down differently on the thrust portion of the crank?

BTW it is a 351M (351 crank as well)

 

I think you may have tightened the bolts down too much. I know you probably trusted the machinist but maybe you should plastigauge just to be sure. Could your torque wrench be off, to cause you to overtighten? Your crank is definitely too tight. Maybe someone can give you a better suggestion, good luck

 

Well, tightening the bolts too tight should NOT affect how easily the crank turns. The bolts hold the bearing caps to the block, and, unless they can compress cast iron, they will just hold the caps tighter...
Do the plastigage thing, and check the clearance on the thrust surfaces also. THere IS a spec for thrust clearance, and it should be met within reason.
I don't know how machinists generally do thrust bearing surfaces, but I'd expect ALL clearances on a thrust insert to be reduced/increased the same amount. Now, rods and mains CAN be done at different undersize, i.e. 020 mains, and 010 rods with no problem.
my 2 copper clads..
tom

 

Yeah he has a point you probably cannot torque it so much to cause that kind of problem. He did make a good point on the thrust clearance. I don't know if this would make that kind of difference but I know you are supposed to install the caps as they cam off. Just trying to throw the simple things out there first. Let us know what it was as I am interested in knowing, later

 

All the littles added up to be big, Here we go...............

I had a 14 year neighbor boy as my helper buddy (i did not super vise enough yikes) He attempted to install the thrust bearings on the rear portion of the block, which intern widened the thrust bearings too much which explains why the crank didn't sit in as easy as I thought it would.

After I removed the crank and bearings to try to fix the thrust bearing, I noticed the damaged which was done to it. (not fixable) I called the machinist and told him about one of the bearings being the wrong size. I guess it is not uncommon for wrong size bearings be sent. So luckily I am getting a new set of main bearings free. Lessens learned!

One more thing that I thought about. I first thought that the oil I was useing for all bearing intallations was too thin of an oil which might have made the driveshaft too tight (5W-30 castrol) Does anyone have any recommendations on oil that I should use for building my engine up? It is not too late for me to change so any suggestions will help. I heard to use 90-140W gear oil and one guy even said to use vasoline on the bearings?.... And fill the engine up with what ever prior to running it
Book says to use what ever oil you plan on running during engine break in on the bearings as well.....

 

as far as lube ior your bearind during rebuild, i use stp or vasaline on the bearing....have had no trouble with either..

 

There is an item called 'assembly lube' that will stick to the surfaces for a long time.. in case you have to wait for parts.. repaint.. whatever. It is made by one of the oil or bearing companies. I just used motor oil as I had no delays planned when doing engine work. If you had a machine shop, and pre-built short blocks, you'd use assembly lube. Make sure to put some light grease, or oil at least into the oil pump to assure a quick prime and thus quick oil flow(it''ll help the gears seal to the housing and to each other).
tom

 

STP is good, assemble lube is better.

 

Lucas Oil conditioner is a great assembly lube, and you just dump whats left in the crancase, (No waste)

 

Assembly lube is by far the best. It's made to do exactly what you need it to do, cushion and lubricate at startup. Get some Crane cam assembly lube (dark grey in color) and "paint" each and every lobe. Don't forget the cam gear. Make ABSOLUTELY, POSITIVELY sure you adequately oil the piston pin areas with assembly lube. The skirts and rings need light assembly oil, not too much. Your oil pump should be disassembled and cleaned and filled with about an ounce of assembly oil. This will help "vacuum prime" the pump. You have to prime the oiling system before startup, preferably while it's still on the stand but within a few hours of actual startup.

 

Jwtaylor is correct with the platicgage. Its cheap, and does a fairly accurate job of showing the crank bearing clearance. Don't continue assembling the engine until you figure out what went wrong. Buy a cheap dial caliper (about $30) and measure all the crank main journals. If one is turned wrong take it back and have it fixed. Take each main bearig cap off one at a time, try turning the crank after each cap is removed to try to find where the problem is. With all 5 caps torqued in place, take the #3 thrust cap off first, leaving the others torqued in place. The crank will spin freely when the suspect cap is removed.
All the mains should be turned the same amount, and a good mechanic or machinist will have pride and check their work. Sounds like the cranks turned wrong, or a main cap is on backwards (notches for bearing locators go on the same side,and there usually markings on the caps pointing 'forward'. With your new dial caliper measure the distance between crank thrust surfaces, and measure the thrust bearing width, or simply try inserting a feeler gauge between the thrust bearing and crank thrust surface. I'm guessing the clearance should be 0.01-0.03.
A properly installed crank with main bearings torqued, no pistons or rods, will turn over by hand with some resistance. Install the crank without the rear main seal, check for hand rotation and tight spots for bent crank. If all ok then disassemble and go back in with the rear main seal.
Lubriplate engine assembly lube is perfect on the bearings, and some folks also apply engine oil the the crank journals, then assemble. Also use the lube or engine oil to prime the oil pump prior to installing on block. Take cover off oil pump and fill rotor area with lube, then reinstall cover with a touch of locktight on the cover bolts. I like the lube as it doesn't run back out. Oil used for assembly can be the same as what you will run in the engine, like 5w-30 as was mentioned. If you can't prime the oil system with a drill motor prior to first start up of the new rebuild, leave the spark plugs out, ground the coil wire, and use the starter to spin the engine over. This pushes oil thru all the passages, and fills the carb with gas. Usually several 15-30 second long spins will send oil all the way to the rocker arms. Leave the valve covers off to watch for oil supply.

 

Get rid of the neighbor kid. Or, at least make him watch and don't let him touch anything. I've seen dozens of bearings ruined because someone with a chevy background didn't realize fords don't go together the same way. DF

 

I hate to tell you this but, always plastiguage bearings when rebuild or even on a new engine....

people can make mistakes...

If the crank was undersized by 10 thousandths, then the bearing has to be
for a crank that is machined for that tolerance, anything else and you will get too much play or the engine won't turn without excessive force...

After plastiguaging to confim the FRPP shortblock, we lightly coated the bearings with a mix of MMOil and prelube and retorqued them to spec..

The engine was nice and tight and I could still turn the crank by hand.....(with pistons/rings installed and no endplay...)

usually the order fo operation is this, the machinist will measure the existing
tolerances, and machine the crank to its undersize, then the bearings are ordered to match the crank....or journals...

 

Also is it common for machinist to grind the crank down differently on the thrust portion of the crank?

Not unless the width of the bearing surface (the surface that actually rides on the crank journal) is wider for that particular bearing than the other main bearings. Being that your engine uses bearings that all have the same bearing surface width, then all the main crank journals should be grind to the exact same size.
In the case of a Chevy engine whereas their thrust bearing has a much wider bearing width than the other bearings.... the rear main crank journal for their engines are grind .0005" more than the other main journals.