I recently rebuilt my mk1 engine and also had the crank rebuilt at the same time.

After about 500 miles the engine seized. I've just pulled the engine apart and it looks as if the big end has let go.

I just spoke to LT who rebuilt the crank and they said that when I put the crankcase half's back together, I could have put too much pressure on the crank, which could cause the two halfs of the crank to move and nip the big end bearing up.

Is this possable, or are they just coving them selves.

Just to add LT have been fine, i'm going to send them the crank so they can have a look at it. Just wanted to know what was what.

xstian wrote:I recently rebuilt my mk1 engine and also had the crank rebuilt at the same time.

After about 500 miles the engine seized. I've just pulled the engine apart and it looks as if the big end has let go.

I just spoke to LT who rebuilt the crank and they said that when I put the crankcase half's back together, I could have put too much pressure on the crank, which could cause the two halfs of the crank to move and nip the big end bearing up.

Is this possable, or are they just coving them selves.

Just to add LT have been fine, i'm going to send them the crank so they can have a look at it. Just wanted to know what was what.

Yes, it's feasible,, did you notice any inherent roughness to the engine when it was fired up after the rebuild?
I ask as this would also be an indication that to much strain/pressure had been applied.
Did you heat the casings, and or, freeze the bearings?
Mike

The engine sounded fine right up untill it seized. I didn't heat or freeze anything, everything went together fine, and all the bearings are fine other than the big end bearing.

The crank was tight to go in, but nothing more than you would expect.

xstian wrote:The engine sounded fine right up untill it seized. I didn't heat or freeze anything, everything went together fine, and all the bearings are fine other than the big end bearing.

The crank was tight to go in, but nothing more than you would expect.

Did you have to resort to heavy blows, or was it pulled together with a tool?
Mike

I know this might be a bit after the fact but always check for smooth rotation of the crank after putting the two cases together. If there was smooth rotation then it is less likey that the LT explanation is correct .

If it is lack of lubrication then the piston usually seizes first.

Did you put anything like 'bearing fixant' around the main bearings that would make them not fit flush in their mountings .

The crank and con rod where fine, I had no issures puting it together.

What I wanted to know is, is it possable for the crank to tighten up against the thrust washer and the bearing?

I would have thought that when the crank is pressed together, there is some sort of stop for it to be seated against, and that would be as far as it could be pressed. But not having seen one apart I don't know.

sounds like crap to me.

did you crank turn over nicely by hand before the engine was rebuilt?

Mine was a little stiff initially, so I concluded my main bearings werent seated properly, so I made a jig up using two old crank bearings, the chain adjuster (as a tensioning plate) and the flywheel bolt/primary gear bolt.

this pulled the crank towards the cases and pushed the main bearings into place properly, now it spins over nicely by hand.

but what Im really trying to get at is, if something was going to give (especially at high temp) it wouldn't have been your crank webs sliding along the pin to bind your big end.
the pressure would have also been applied to your main bearings and they would have just slipped into place most likely.

also from the friction I felt when my crank was binding, the engine would have regularly stalled and would have been a bitch to start.

take a few measurements of your crank to see if it really binded, perhaps they used thrust washers that were a little too thick, and that decreased the clearance? I dunno, Im just guessing. or it could have been exactly as they said, Im not sure.

In another life, decades ago, I worked in the test shop for a now defunct Diesel engine manufacturer.
If we had a suspect crank in a unit, while the engine was under test on the "test brakes" we would GENTLY using a centre punch,and light hammer, tap the end of the crank, this would generally, take out and inherent roughness, or binding.
I assume LT, will be measuring all the parameters for the same readings as it left the shop with.
Mike

Well I've sent the crank to them and I'm waiting to hear back. When I know more I will let you know whatr they have said.

Cheers For your help.