Plastigage use 'in-frame'

[tshep]

I'm still planning the measuring task, pan is off, etc. now.
I expect to find a great crank, nicely worn bearings, and if so...
Thought I would re-assemble with the plastigage and new '0' bearings to confirm clearance control JIC.

 

[DieselBound]

Isn't there a spec range? I'd think that one could mitigate any gravity effects by biasing toward the lower value/range?

 

[tshep]

I found a manual that discussed it!
Makes so much sense....

Place .010 shim stock between lower shell and caps for adjacent journals, just snug them up.
Lifts the 3 just a hair or two to ensure journal/upper bearing contact.

Better ideas?

 

[Cougsfan]

If you were worried about that you could put plastigage on both sides of the bearing. I will bet you find no difference in the reading. On a crank, if you are doing on journal at a time the other mains (if lubricated) will keep gravity from being a factor. If you do have a variance from side to side is more likely due to machine runout of the crank. In rod bearings, the rings on the piston have enough friction to negate gravitational effects. All in all, I think you a concerned about something that is not a concern.

 

[sailonner]

To the post, plasti-gage is not so soft as to be significantly deformed by the weight of the crank suspended by the other bearings. ONLY DO ONE JOURNAL AT A TIME!

And to the comments about THE INFERIOR NATURE OF AN "IN FRAME REBUILD.

No, it's not ideal, but if the engine was a runner prior to replacing mains rods and rings. It will go a lifetime again after.

Just be sure to cut that ridge at the cylinder top before the new rings go in, and use the correct size ball hone to refresh the cylinder wall structure. And freshen up those valves and seats!

By "cutting the ridge" do you mean relieve the inner edge of the cylinder hole?
I'll be doing an inframe overhaul on my Chinese 3 cyl. diesel Y385T soon. I bought bnew pison, rings and cyl. sleeves. Don't plan on looking at the mains at all. Wondering if I need to do that on the new sleeves?

 

[RickB]

Just be sure to cut that ridge at the cylinder top before the new rings go in, and use the correct size ball hone to refresh the cylinder wall structure.

I don't think we know what engine is being discussed. An in frame on a sleeved engine could easily include new sleeves, wet or dry.

 

[Bob Rooks]

The answer to your question is no, and not because of gravity. Plastigage is not used on "wet" bearings, and since your in-frame crank will have oil films around it any readings you get will not be accurate. In fact, you may not even get repeatable readings because of that.

 

[jaydee325]

The answer to your question is no, and not because of gravity. Plastigage is not used on "wet" bearings, and since your in-frame crank will have oil films around it any readings you get will not be accurate. In fact, you may not even get repeatable readings because of that.

Plastigauge, Plastic Precision Clearance Gauges

This says you just need to remove excess oil. Plastigage strip is held in place with a smear of grease.

Orientation of the engine is not mentioned, so I assume an in frame use is no problem.

 

[Bob Rooks]

Plastigauge, Plastic Precision Clearance Gauges

This says you just need to remove excess oil. Plastigage strip is held in place with a smear of grease.

Orientation of the engine is not mentioned, so I assume an in frame use is no problem.

Grease? That ultra high viscosity stuff? Maybe a small dollop of Vaseline?
So, "remove excess oil" means no visible oil = "dry".

 

[tshep]

Pistons, ridge are not involved, just the crank. (Bores seemed fine during recent head work.)

For the crank, actually, the fitting is going very well, and measurements fairly repeatable.
I'm 'jamming' the one or two adjacent journals into their old (worn small) bearings, with the new one under test in place (dry, pushed in while crank was 'down'). Then with no rotation, I torque in the new lower to measure. It seems like six times the work, but I learned a reasonable sequence quickly.