Stiff Big Ends

[JamesHannaford]

Hi all,

New to the group so apologies if I’m going over old ground / posting this is the wrong place…

I’m in the process of building a ‘warm’ 998cc engine to put into my Morris Minor (bored out from 948cc, flat top pistons, cooper head etc).

After having received everything back from the machine shop I appear to have fallen at pretty much the first hurdle (or perhaps second!) - I’ve installed the crankshaft which rotates freely. I’ve put the pistons in, and the first two con rod big ends, all torqued up still allow me to move the crank, albeit with a bit of resistance (mainly from the new piston rings I guess). However as soon as I put any torque on the third and fourth big ends, it makes the crank incredibly stiff - when they’re both done up I can’t really move the crank at all, even with a spanner.

The crank was ground to 10thou under and there are new bearings to suit.

I’m going to speak to the machine shop, but this forum has been such a hive of information I thought I would also try here in case there are any bright ideas!

Many thanks,

James

[paul 300358]

Sounds to me like you have put the big end caps on the wrong way round

[philthehill]

I agree with the above.
also
Have you got the rods fitted to the right crankshaft journals? The rods are offset relative to the crankshaft journals.

[JamesHannaford]

Thank you for the quick responses - I did check the rods are in the right place and yes, they’re all correct (took me a while to work out what was different looking at the image in the Haynes manual!).

That’s a good point on the caps - I think I kept them as they were removed but I was in a spiral of despair yesterday, so may well have inadvertently mixed them up. I’ll double check when home later.

Many thanks for the help

[philthehill]

The caps may be fitted to the right rod but are they the right way round on the rod??
The rod and cap are usually stained opposite and against the slot for the tang of the bearing and is a good indicator of the correct way round the cap fits.