Plastigage use 'in-frame'

[tshep]

I know it's normally used on an upside down engine, journal weight on 'upper' shell so all clearance is at 'lower' shell when torqued.
When the engine is right side up, in frame, what is a good process?
How can I ensure the upper shell is at zero with the journal?
Should I remove all other uppers while checking this one? (Supporting ends, then 'jacking up' a weight near this journal?) (Or just expect the crank to flex enough for contact?)
THX!

 

[Richard]

Wow, it's probably been 40 years since I've used it.... (on an engine that was upside down as you suggest)

HOWEVER, since it's measuring the gap in there, I can't imagine that it would make a difference what the orientation of the engine/crank may be??

(I'm not a mechanic)

Maybe someone will correct me and I'll be reading with open eyes because I've got an engine that I've debated on doing while engine is in-place which means I would have done the measuring from the bottom so to say.

I'll be intrigued to hear other thoughts but I still can't believe it really makes a difference. After all, a gap is a gap is a gap, no? (if gravity or engine facing down makes a difference then I'd expect there to be other/larger issues to contend with)


???

 

[tshep]

HOWEVER, since it's measuring the gap in there, I can't imagine that it would make a difference what the orientation of the engine/crank may be?

It really doesn't, but for that darn (blessed) gravity!
The basic instructions all assume gravity is holding the crank and upper shell down on the engine stand.
In frame gravity breaks things!
And allows space between crank and upper shell.

 

[dodge man]

I’m confused. Are you talking the main crank journals? I also don’t think it matter on the orientation. If it’s on a engine stand and your worried about it flip it over and do it so the engine isn’t upside down.

 

[TractorGuy]

It won't matter.

What is the purpose for the in frame repair?

 

[John0829]

Yer over thinking it, been doing in frames for years and always used plastigage without issue to verify what I already knew by using a micrometer. However the bottom line is if you are doing an in frame there is nothing you can do to change the clearance, you have to go back with what came out of it because if your shaft is tapered or out of round then it has got to come out or your wasting your time and money. That is unless you are doing a shadetree patch to get rid of it.

 

[RickB]

I’m confused. Are you talking the main crank journals? I also don’t think it matter on the orientation. If it’s on a engine stand and your worried about it flip it over and do it so the engine isn’t upside down.

Not familiar with the term "in frame" in the thread title, are you?

 

[Jerry/MT]

Not familiar with the term "in frame" in the thread title, are you?

"In Frame" generally means the block is installed in the vehicle while crank bearings inserts are being replaced. As one of the other posters said, you have to verify that out of round and taper of the journals are within spec limits or it's waste of time and money.

 

[TractorGuy]

You don't generally perform and in frame overhaul if you have any knocking or lack of oil pressure problems. It is usually reserved for freshening an engine with excessive blowby or ring wear but otherwise running okay.

You are pulling the head and the pistons and rods in the frame. There is no way to get a mic on the main journals so plastigage is a decent indication if your clearances are too far out of spec. You can generally roll new mains in while you are in there but sometimes you just replace the rod bearings, rings, and do a valve job.

You won't get brand new engine out of it but if the mains aren't damaged you can extend the life of a worn engine. The last one i did for an employer he got another 90K out of it with abusive operators. It was puking so much oil before it was unusable.

 

[CalG]

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!

 

[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.