Interpret BEB oil clearance measurement (1 Viewer)

[tweeek]

Question for those who have done their BEBs on a 1HDT. FSM states

.036-.054mm standard.
.037-.077mm U/S

But also states 0.10mm as max oil clearance.

My first plastiguage is .076mm. STD Taiho shells.

I am out of standard spec but under max clearance... soooooo am I good? I guess I dont understand why there is different clearances for U/S bearings but a max of .10mm for all.

 

[tweeek]

Ttt... anybody?

 

[Jan-78FJ40]

I would guess that for undersized (U/S) bearings they take the crank grinding into account and allow for greater tolerances.
If I understand you correctly, you have 0.076mm clearance on standard bearings, which would be too much.

 

[tweeek]

I would guess that for undersized (U/S) bearings they take the crank grinding into account and allow for greater tolerances.
If I understand you correctly, you have 0.076mm clearance on standard bearings, which would be too much.

Then why state maximum clearance of .10mm?

 

[Jan-78FJ40]

Then why state maximum clearance of .10mm?

Don't know.

 

[Locked79]

Righto, I'll try and explain this as best I can and how I understand it.

I'm fairly sure that when an engine is newly built in the factory, there are a variety of STD size bearing shells which are then mixed and matched to get the best oil clearance. They are numbered almost like head gasket thicknesses, with slight variations in size to make up for some manufacturing tolerances and get the oil clearance more precise.

When you go OEM U/S, or even Taiho STD size, the whole set ARE the same size with the same oil clearance. The greater oil clearance is to allow for manufacturing tolerances.

But coming new from the factory, the oil clearance would have been between 0.036 - 0.054mm when new. The 0.037 - 0.077mm takes into account and newly ground crank and new bearings. The 0.1mm allowable oil clearance assumes used bearings and crank with slight wear. Since you've got new bearings on a used crank, I would run with the 0.1mm max oil clearance. Call it good.

I hope this makes sense. I know what I'm trying to write, just comes out a bit different haha.

 

[lostmarbles]

The way I read it...

At 0.076 mm clearance you're GOOD because you've still got 0.024 of wear left before you reach the limit of 0.1mm clearance.

As for the "standard clearance figures", I'd just ignore them altogether..

 

[tweeek]

Well this is all good news and what I want to hear.

One of the techs at Radd suggested that he has never seen one out of STD spec before. I redid the test and cleaned the crank and new shells really good and dry. My reading the second go around was closer to .56 which makes me feel alot better. At this point I ordered some new bolts anyway to make sure that the threads arent stretching from being torqued a few times, which may help a little as well. I am thinking there must have been some lubrication still present on the crank when I did my first plastigage, which seems to make a difference.

Either way, going forward hopefully good.

 

[ozwallaby]

Does anyone know if the 1hdt (or ft/fte) has a nitrided crank...... I've asked this question before in several places and it seems nobody can give a definitive answer.... the reason I ask is if they are nitrided then grinding them undersize will take the hardening treatment off.... this may be well and good but it may make the crank susceptible to higher wear rates....

 

[jzilla]

Did you take the clearance with the engine on a stand or with the engine installed in your truck?

 

[Jan-78FJ40]

Did you take the clearance with the engine on a stand or with the engine installed in your truck?

Curious, why do you think that would make a difference?