MGB: Engine Assembly Problems

I've started putting my engine together, I put the crank in, torqued it to 70 ft lbs. I could turn it by hand.... so I put the pistons in, tigtend the big end bearings finger tight, ok could still turn the crank by hand...... torqued one cap down to 33 ft lbs, crank still turned, torqued down second......crank WONT turn?? so thats my problem, I can have one big-end cap torqed down, but as soon as I torque another one it won't turn, and it doesn't matter which one gets tightend.


I was wondering if haveing the connecting rods in the wrong way could cause this(some sort of binding of something) because I think I have them the wrong way????

You are doing it right!! Now I would use Platigage and check it all out!! It sounds like there is a clearance problem!!

Did you mix up the caps?

Had the same problem when installing a new crank. A prior rebuild had punch marked the number 3 rod end cap wrong. You should plastigauge one or two of the main caps and rod end caps, and always check for free rotation of the crank after every cap is installed. That way the offending cap is pointed out quickly. I think Kimberly is right on, if the caps weren't punch marked clearly, it is easy to lose track. The old crank was a looser fit, but as wear occurred on the thrust washers, the reversed rod cap caused a binding when the clutch was put in that would stall the engine at very low idle..

All the above advice is good. Someting Did you make sure the bearings were the right size.

How are you turning it? By the flywheel? By putting a socket and bar on the big nut? If you're just trying to grab the end of the crank and turn, you won't be able to, unless you are beafier than me.

I did plastigague the mains and big ends, and they all seemed good. I was turning it by hand. the machine shop got all the bearings for me, and there the same as the old ones. So i'm maybe there good still.


Also does the pistions have to go in a certain way? the haynes manuals aren't very clear

Check all the above first.

I had the same problem, plastiguage gave perfect clearance readings, and fooled me for a little while. My problem was that the main bearing caps were stretched toward the bottom. Until they were removed they retained their roundness because the bolts held them in place. The metal, however, was hightly stressed and when the bolts were removed the caps pinched inward at their open ends. This in turn squeezed the ends of the bearings against the crankshaft on the sides and bound the shaft to the point where it wouldn't turn. I had to have the block align bored and that cured the problem.

Did you check the ring gap?

ok good news everyone, it was just a case of wrong cap placement.....so everything is back on track and going good, thats for the help, I'll keep you all updated :)

Thanks for the update Adam. It's really helpful when people let the BBS know what worked and what didn't, what symptoms were red herrings, etc.

I'll second that!

I hope you didn't damage the bearing shell!!

yeah, I know what u mean about following up, so I always try too and I check the bearing, it looked good. when the cap was on I couldn't turn the crank so if there was any damage it was not apparent