935 replies to this topic

[panky]

Sounds like some of the end caps or con rod ends are distorted

[HUBBA.HUBBA]

Sounds like some of the end caps or con rod ends are distorted

What could cause that?

[panky]

They could have been over-torqued in the past and 'squashed' them or the engine over revved excessively and elongated them. The other possibility is that the caps and rods are miss-matched so the bores don't quite line up. Is there any sign of a step between cap and rod when they are put together?

[Steve220]

Are they the right size for the crank milling? Did the company that did the engine work give you a crib sheet of what bearing sizes to use?

[HUBBA.HUBBA]

Just had a look and yes there is a sign of a step. Enough to catch my nail on. The caps and rods are matched (well the machining marks on the side match). Insistently the wear marks on the new bearings are by the joins. I wonder if I could just sand the area when torque down to get them inline again

[Steve220]

Im more concerned that the machining hasnt been done correctly! Had my block and crank done and it almost fell together in the right tolerances.

[HUBBA.HUBBA]

Are they the right size for the crank milling? Did the company that did the engine work give you a crib sheet of what bearing sizes to use?

They didn't need to mill the big end part of the crank just the mains. They supplied the bearings for me. 2 of them are fine.

[HUBBA.HUBBA]

I would have thought if the crank wasn't ok, the wear markings in the new bearings would be all the way round, but it is in just one area.

[HUBBA.HUBBA]

The step is as if the cap is now slightly staggered across. I wondered if the bolts could cause a misalignment somehow.

Edited by HUBBA.HUBBA, 22 October 2017 - 02:30 PM.

[nicklouse]

i would be getting them measured.

[Steve220]

If youre not 100% sure what youre doing, get an engine builder to do it.

[panky]

Have you tried swapping over the caps on the two rods that are tight.

[HUBBA.HUBBA]

If youre not 100% sure what youre doing, get an engine builder to do it.

Thanks for that, but I'm not one for giving in. I know this is just my second engine rebuild, but I just didn't come across these issues the first time round. I'm not going to learn anything passing it to someone else to do.

I'll go and pop over to the machine shop in the week so they can measure it. In the mean time I might just try the good ones further up the crank and see what they are like.

[HUBBA.HUBBA]

Have you tried swapping over the caps on the two rods that are tight.

No, only because the machining marks match up. I'll try it and see. Even wondered about just turning the caps round so the tabs aren't on the same side  

[HUBBA.HUBBA]

Well who'd a thought it. They're in and they move. Transpires 2 of the caps must have swapped themselves over in the middle of the night ages ago. Never thought the machining marks would match 2 pairs of rods.

Phew

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