Engine Rebuild

[martynharrison]

Well, after a bit of entertainment involving piston rings and the importance of grinding all the deposits out so the new rings have room, I'm finally fitting the pistons properly.

 

Next issue, the big ends go together in the correct way with the tags on the same side and the prongs on the base of the con rod shell point at each other, but there is a distinct gap between the bearings and the crankshaft. Can't see from the angle they're in but I'd believe half a millimeter.

 

Which would be about 20 thou, I suppose.

 

So I had a look at the old bearings and they have a part number ERC2589 and 5051 and 020 so I am 99.9% sure this means the crank has been reground -0.020 inch and therefore I need +20 thou big end bearings, yes? I presume the con rod end can stay standard and merely have a thicker bearing?

 

This is all terribly previous, I've only just got the ring compressor and thought I could do most of the rebuilt over the B/H weekend, but hey-ho.

 

On the same front, I have some "cam lube" and the packet says "flex to mix". Does this stuff go off then, once mixed, and if so, how long does it keep for? I don't really mind bringing the cam back out and doing it again with the lifters once the heads are on, but it would be nice to have some idea what that's all about.

[Andy Moltu]

BE & main bearings are usually stamped to indicate the undersize they are intended to fit. (Ie a grind to -20 thou will need -20 though bearings which is usually stamped on the reverse side of the bearings) If you have got gaps like these & they don't close on torquing up you will need to check if the bearings shells are sitting cleanly in the capsAlso check the caps are the right way round. Another possibility might be the big ends have been ground to a different undersize to the mains. You may need to get your crank re measured if there is any doubt. (easy now but a major pain in the arse if you have to do it after the engine has started & seized or rumbles)

 

Cam lube just needs mixing up to even up the suspension rather than to chemically activate it. It should keep.

[marvmul]

Well, after a bit of entertainment involving piston rings and the importance of grinding all the deposits out so the new rings have room, I'm finally fitting the pistons properly.

 

Next issue, the big ends go together in the correct way with the tags on the same side and the prongs on the base of the con rod shell point at each other, but there is a distinct gap between the bearings and the crankshaft. Can't see from the angle they're in but I'd believe half a millimeter.

 

Which would be about 20 thou, I suppose.

 

So I had a look at the old bearings and they have a part number ERC2589 and 5051 and 020 so I am 99.9% sure this means the crank has been reground -0.020 inch and therefore I need +20 thou big end bearings, yes? I presume the con rod end can stay standard and merely have a thicker bearing?

 

This is all terribly previous, I've only just got the ring compressor and thought I could do most of the rebuilt over the B/H weekend, but hey-ho.

 

On the same front, I have some "cam lube" and the packet says "flex to mix". Does this stuff go off then, once mixed, and if so, how long does it keep for? I don't really mind bringing the cam back out and doing it again with the lifters once the heads are on, but it would be nice to have some idea what that's all about.

Do you mean half a millimeter between the shell bearings and the bearing surface of the crankshaft?

Sideways sliding movement (about a mm or more) of the conrod on the crankshaft is normal.

Plastigauge (Plastigage in some countries) is a very accurate way to check the clearance : it is simply a filament of some plastic material, you need only one filament of about 30cm. You put a piece of about 2cm between the bearing surface of the crankshaft and the conrod and torque the bolts down. After removing the conrod cap, you measure the width of the sqeezed filament and compare this with Plastigauge scale to know the clearance.

[martynharrison]

Yes, on talking to S&S the old bearings were 020 = 20 thou oversize, and some more careful checking reveals that the mains were also 020 even though it seemed a quite reasonable fit.

 

Basically the crank has been reground to 20 thou and therefore needs thicker bearings in both places.

 

Good news about the cam oil then, I can fit the cam and then fit the lifters once the heads are on.