Crank concentricity
 

Just going through a dry fit and measuring clearances and have a quick question. Main journals 2&4 measure .002 and if rotated 180* measure .003 plus, the crank measures with in spec so I have two journals running out a little.

Anythings to worry about? was thinking of getting a set of X bearing to level it out!!

I left the crank in the block and put a DTI on 2&4 and get .01mm/0004 inch not much of an error?
https://cimg4.ibsrv.net/gimg/www.off...d75c63b6ac.jpg

If you're in Florida bring it and I'll straighten it no charge if not you're welcome to send it UPS and I'll take care of it for you. Sincerely Laz
P.S. stop down and see us at the Miami Boat Show booth F419 same as last year

WOW what a super cool and generous offer , being in Canada the shipping would be more than the crank is worth, lol. Wish I was in Florida right now it's freaking cold up here right now hahaha.

If it turns free send it. They straighten new cranks with a Hammer and round chisel same as billet camshafts. Are you having a problem with run out or out of round journals?

It turns free I was just checking the clearances before I assemble it and noticed 2 & 4 where on the smaller side of what I like. Just not sure if 1/2 thou is anything to worry about. 100% run out it's not out of round!

.002 is a little snug are you using a good bore gage? You can try shuffling some bearings around and check again.

The way I checked it was to do a dry assembly with the new bearing, disassemble and use Clevite plastigage to measure the clearances, on 2&4 I rotated the crank 180* and rechecked. I then removed all the caps and using a DTI checked all the bearings 1,3&5 run true and 2&4 have .0004 run out.
I like your idea of swapping some bearing around but I still have .0004 runout and not sure if that's a problem or not.

.0004 is nothing to worry about. Actually it is pretty good :) Do you have oil on the bearings when you are checking the clearance ? That will make them a little tighter.

I see what you are doing now with the 180* Think you are good with what you got for measurement I didn't know you where using plastigage.

you cannot get very acurate measurements with plastigage.also an endurance bbc needs more than .002.

Yes it does I agree with that .002 is to tight, and I have now found out your right plastigage ain't to accurate!!

So today I've done some more measuring :)
measured crank journals:
#1=2.7476
#2=2.7480
#3=2.7478
#4=2.7478
#5=2.7475

Assemble journals with bearing:
#1=2.7516 clearance= .0041
#2=2.7519 clearance =.0039
#3=2.7520 clearance=.0042
#4=2.7518 clearance=.0040
#5=2.7520 clearance=.0045
https://cimg2.ibsrv.net/gimg/www.off...3daf6d804f.jpg

https://cimg8.ibsrv.net/gimg/www.off...28a14542d8.jpg

I then installed bearings 1 and 5 and used a better DTI checked my run out on journals 2,3 and 4.
#2=.00025
#3=.00005
#4=.00035
I have no way of checking the concentricity of the block journal which I'm now thinking is my problem?

Not sure if I understand exactly what you think the problem is ?

Yeah penny just dropped......................... it's the Plastigage whats giving me odd reading :)

Assemble journals with bearing:
#1=2.7516 clearance= .0041
#2=2.7519 clearance =.0039
#3=2.7520 clearance=.0042
#4=2.7518 clearance=.0040
#5=2.7520 clearance=.0045

That's more than I would want make sure your not making a mistake with something I doubt the plastigage is that far out.

Try this. Get everything good and clean and oil free. Sit the crank in the block. Put the front main cap on but do not torque it yet. Take a .003" feeler gauge and measure it to make sure it is actually .003 and make sure there are no burrs on the edges for the first inch or so. Shove the feeler gauge in between the front main journal and the bearing in the cap and snug it down by hand. Then torque it to specs. Now if you can pull the feeler gauge out you have at least .003" clearance. You can then try a .004 and see what happens.

I am not sure who told me about this method but I tell some of my DIY customers about it as a good way to double check what the plastigage is telling you. Of course you can only use it on the front main.

I prefer using my Sunnen bore gauge.

I thought I would give this thread a conclusion!!

I took the block and crank to the local engine machine shop for them to check, they checked the block journals for straightness and all was good :). They then did the same checks as I did and got readings .0005 smaller with there bore gauge than I did but the same diameter readings of the crank journals. So I'm happy with the results around .0035 clearance. I believe temperature played a part in my first plastigage reads.
To save on heating costs I let the workshop drop down to 5*c at night, I checked it first thing in the morning the first time and the block and crank was "cold", I've have the heating set to 20*c since and I get consistent readings with the plastigage showing .003/0035.

Thanks for the pointers everyone :)