Thread: What have I done wrong

Did you do any of the following:

- put caps back onto the same rods they came off and the right way round.

- ditto above for mains caps.

- put rods back onto the same pots they originally came from.

- plastigauge the rod caps for clearance.

- ditto above for mains caps.

- assume you used an assembly lube like Nulon L90 on all the journals.

Andrew

As above.

Wear itself in?.....yes......but not in a good way.


cheers

Hi,
My answers are as follows:
The big end and main caps were not mixed up.
The crankshaft turned freely before the piston assemblies were put back in - easy to turn by hand. So I don't think the main bearings/journals are the problem.
Yes, Penrite assembly lube used on all bearings.
No, I haven't used plastigauge - will buy some tomorrow. Will also remove 3 and 4 big ends to confirm that they are the cause of the tightness.

Another question - are main cap bolts and the big end bolts single use items? Have just read on a RPI site that I should have replaced both sets of bolts.
Regards,

If you're rebuilding then I would be replacing all these bolts with at least new ones but preferebly ARP studs, plus the heads with studs. It can tighten slightly as you are pushing the rod over centre at TDCbut as you said, remove one pair of caps at a time to slowly eliminate which one is the issue. But I'd be checking everything with plastigauge anyway.

Worst case scenario is if you've changed the crank or rods that a rod is out of line in the bore.

Thanks for your advice guys. I'll get back to it and let you know what I find.

Will also buy new bottom end bolts - have already got new head bolts.

PLEASE at least swap at head bolts for studs. This is the one area that will have issue from the bolts. Especially since the new bolts are TTY.

Hi Guys,
An update on my problem. On rechecking the tightness on cylinders 3 & 4 I found that no 3 & 4 bearing caps had been really badly scored by the oil feed holes in the crankshaft when turning the engine over by hand. All other bearings (including the mains) are unmarked.
I think I mentioned that a local engine shop had polished the crankshaft for me - clearly they did not do the job properly. I removed it and took it back to them this afternoon and they are going to re-do the job free of charge - but that is not much consolation, as I now need to buy a new set of bearings to replace the cactus ones on 3 & 4 big ends.
Al together a pain in the Arse, but better to make sure it is right the first time around I guess.
Thanks again for your advice.

heres how I do a crankshaft if Im working with a crank of unknown quality machining, I do ALL of this prior to installing any of the seals or other bits that go onto the crank.

with the crank OUT of the engine

1. do the bearing shell nip tests on the big ends and mains inspect the shells
2. bearing blue onto the crank
3. assemble the big end as you would for the plastigauge test
4. disasemble then inspect the bearings for transferance of bearing blue
5. conduct the normal plastigauge tests (repeat at 90 degree intervals for each end if the bearing blue transferance was not "clean")
6. repeat for ALL big ends (pattern out the parts as you clean them up so you cant mix them up after this process)
7. without any of the rods on repeat for the crank mains
8. check the crank end float

If Its all OK at this point I assemble the rest of the crank bits and seals then install as per the normal instructions.

Dont forget to oil the running surfaces of the components and the bearings with assembly oil (80/90 will do) prior to putting everything together