Tight engine problem

sphanna

sphanna

Well-known member
I am building up a B block engine. Main bearings are baffling me. I have all shims to give .0015 to .002 clearance on all three. I checked each bearing individually and crank turned easily. When I torque to specs of 80 F# per Les Andrews, The engine locks up. I can break it loose and it turns fine. Let it sit and try again and it is locked up again. Break loose and it turns OK again. Also if I turn it backwards it locks up again. All clearances are as above and each bearing turns free until I get all bearings torqued I also had each bearing torqued when I checked the clearance with plastigage. Jim Shields lists 55 F# torque. I am thinking I will use about 65 ft-lbs. What do you guys recommend for torque and shall I just get some shim stock and add .001 to each cap or until I find one that frees it up? The strange thing to me is that once it frees up it turns like it should until it sits for more than a few seconds. Every thing is Lubriplated up.
 
Gerard, I don't know what you mean by "crankshaft indexed" The engine was running fine with about 12000 miles on it. Balanced crank, lightened flywheel. No problem with it but I put an AER engine in my Fordor and decided to check the B engine that was in it. Found some scoring in cylinders and decided to rebore and re Valve with adjustable lifters, etc. Crank and rod journals and bearings untouched. Showed no wear.
 
sphanna said:
I am building up a B block engine. Main bearings are baffling me. I have all shims to give .0015 to .002 clearance on all three. I checked each bearing individually and crank turned easily. When I torque to specs of 80 F# per Les Andrews, The engine locks up. I can break it loose and it turns fine. Let it sit and try again and it is locked up again. Break loose and it turns OK again. Also if I turn it backwards it locks up again. All clearances are as above and each bearing turns free until I get all bearings torqued I also had each bearing torqued when I checked the clearance with plastigage. Jim Shields lists 55 F# torque. I am thinking I will use about 65 ft-lbs. What do you guys recommend for torque and shall I just get some shim stock and add .001 to each cap or until I find one that frees it up? The strange thing to me is that once it frees up it turns like it should until it sits for more than a few seconds. Every thing is Lubriplated up.
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Normal. It will stop being tight when it is run some.
 
I would suspect the crank seals are a bit tight. I'll assume they are new, are rope type and the engine has them. Haven't had one apart so can't be certain.
 
I thank you all for wonderful help. Dave72dt, seals are not installed yet. Only crank bearing caps on unassembled block.
 
sphanna said:
I am building up a B block engine. Main bearings are baffling me. I have all shims to give .0015 to .002 clearance on all three. I checked each bearing individually and crank turned easily. When I torque to specs of 80 F# per Les Andrews, The engine locks up. I can break it loose and it turns fine. Let it sit and try again and it is locked up again. Break loose and it turns OK again. Also if I turn it backwards it locks up again. All clearances are as above and each bearing turns free until I get all bearings torqued I also had each bearing torqued when I checked the clearance with plastigage. Jim Shields lists 55 F# torque. I am thinking I will use about 65 ft-lbs. What do you guys recommend for torque and shall I just get some shim stock and add .001 to each cap or until I find one that frees it up? The strange thing to me is that once it frees up it turns like it should until it sits for more than a few seconds. Every thing is Lubriplated up.
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This happens with 3 bearings it will turn 3 times harder than one. Also the guys that grind the cranks now days put to much pressure on the center main when they grind them. The crank springs some when grinding lots of them run out at the center main, which makes it harder to turn. I would not worry to much about it. Just run it slow when it gets to operating temp shut down, then let it cool down and do it again a few times until it loosens up.
 
A crank with only 3 brgs should turn quite easily with all the mains torqued and no seals. Is there any end play? .0015 clearance just sounds too tight to me.
 
Dave72dt said:
A crank with only 3 brgs should turn quite easily with all the mains torqued and no seals. Is there any end play? .0015 clearance just sounds too tight to me.
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There should not be any "seals" installed except for the front timing cover seal and oil pan. .0015-002 is the factory specs for an A or B engine.
 
I have decided to take the pistons off the rod so that I can temporarily reinstall them on the rod journals so that I can rotate the rod on the journal. I am installing just enough shims to allow the rods to move without drag. I may also do this with the mains individually without the rods connected to adjust by feel. I have done 5 engines in the past many years ago and never had this trouble. I trust my feel better than plastigage. The engine was running fine for 12000 miles and showed no crank and babbitt wear, so I don't think there is any major problem with the crank. I am not too impressed with plastigage as I know they all measured .0015 to .002. Thanks to all.
 
An inside mike or bore gauge may give you more info on weasr it's tight at. Just because it's within spec where the Plasitgauge was, doesn't mean it's within spec all the way around. In any case, get the crank dialed in before adding rods to it. Fresh babbit, check the chamfer for the radius of the crank journals at the edges.
 
sphanna said:
I have decided to take the pistons off the rod so that I can temporarily reinstall them on the rod journals so that I can rotate the rod on the journal. I am installing just enough shims to allow the rods to move without drag. I may also do this with the mains individually without the rods connected to adjust by feel. I have done 5 engines in the past many years ago and never had this trouble. I trust my feel better than plastigage. The engine was running fine for 12000 miles and showed no crank and babbitt wear, so I don't think there is any major problem with the crank. I am not too impressed with plastigage as I know they all measured .0015 to .002. Thanks to all.
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Are you using a couple of drops of oil on the plastigage, if not it will not give you a true reading. As the boys said, it sounds about right. If the the crank sticks, and you break it loose, and it turns easy, and when you it stop
again, it sticks, that is about right, I think you are about .001 off on one side, of it not sticking, after being turned. Herm.
 
Back in the mid 80's I bought a basket case 29 rdstr. The chassis was restored with a newly rebuilt "B" motor with a C/B crank. The motor was so tight I had to stand on the crank to get it to turn. I didn't run the motor until 2005 when I decided to install it in my 31 Cabby. Before installing it I test ran it in a chassis. Again It could not turn it over with crank. The starter would turn it & it ran fine. After being shut off after a 10 min. run the starter would not turn it over until it cooled down. I ran it like this 20-30 times, it freed up & would start when it was warm. The motor now has 8-10,000 miles & runs like a clock & doesn't leak a drop.
 
I'm in the same boat. Used plastiguage on the mains. Got 1.5-2 (per LA)and now it's so tight, I need the crank to turn it. Problem is, now I've got to install the pistons with new rings. Theirs no way I'm going to check the rods the way it's sitting now. Should I add .0001 shim on one side when I find the offending journal and say to hell with any more plastiguage?
Thanks,
Pete
 
Peter J said:
I'm in the same boat. Used plastiguage on the mains. Got 1.5-2 (per LA)and now it's so tight, I need the crank to turn it. Problem is, now I've got to install the pistons with new rings. Theirs no way I'm going to check the rods the way it's sitting now. Should I add .0001 shim on one side when I find the offending journal and say to hell with any more plastiguage?
Thanks,
Pete
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Hope you used a little oil on the plastiguage? Always check plastiguage on the crank, not on the babbitt! Do one bearing at a time, while the others are loose. If you have a heavy drag, put in the 1 thousands shim on one side, as long that is the side with the least amount of shims. .001-50, to .002 is the +, or - limit, if you are having trouble turning it over with those clearances, you may be closer to .001 thousandths. If you still have trouble, call me anytime. Herm 515-546-4551
 
I'll sure give it a try. Had the plastiguage on the crank but I'm not sure it's totally round so maybe I checked in a low spot. Anyway, I'll relieve the pressure on the mains and add .001 to the low side and go from there. I was pretty close to .001 on a couple of them.
Thanks,
Pete
 
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