Bottom End rebuild Advice

**smithy010** · 27-10-2006, 05:43 PM

Hi all,

I'm rebuilding the bottom end of my diesel. I've got a new second hand crank which i've put the micrometer over and it measures well as standard.
I'm just wondering, when i put the new standard bearings in, should i do that plastigage thing? it won't affect anything will it?

Cheers

Smithy

**h100vw** · 27-10-2006, 07:28 PM

Not that I build loads of engines. But if you are happy the crank measures as std, fit new bearings with plenty of oil on them and away you go.
Gavin

**Oneofthegreats** · 27-10-2006, 08:51 PM

IMO I would still check the clearances with plastiguage on both the mains & big end's. Even if they are standard size bearings & the crank journals measure up. Remember to check the crank main's & big end journal's in two spot's, 90 degress apart. If you've got the tool's also check both the main's in the block & the big end's in the rod's to make sure all is round. You never know, you might have a big end out round. Touch wood.

Once you've measured all the bearing's then check the end float of the crank(if you've got the tool's) as this is often overlooked by alot of people on alot of engine's, especially with auto trans, as not only does the trust bearing wear out, the crank thrust surface can wear out too.

Also check the clearances dry. Don't put any oil on anything when you're checking measurements & don't turn anything. Once you've check it, clean it all down, lube it up & away you go.

Before you put the crank in, also check the rear main surface as I've seen the seal can get very hard over long period's of time & eat into the crank's surface. Might need a speedy sleeve.

brackie · 28-10-2006, 05:28 AM

It's good that you used a micrometer to measure and check the big end journals, Smithy. Plastigauge is good but a fine touch with the mic. is better. As well as checking for ovallity, look for scoring. If it's light you can have the journals polished. On reassembly cleanliness is next to Godliness. Work on a spotless surface with cleaned tools and lightly oil the shells as you fit them. Check for bearing crush too. (Tighten to torque if they're not stretch bolts and slacken the bolt off on one side. You should be able to get a 2 or 3 thou feeler between the conrod flanges.) Remember the stress that diesel cranks have to endure and fit everything carefully and to the correct torque.