Always...Always check your bearing shells

[Crofter]

I would be reluctant to torque the cap bolts with that much crush. I would worry about distorting the rod and cap and or the bearing shell. I have seen a figure of "approx. .001 inch" crush which would theoretically result in a tad over 3 thou. gap at the part line with one nut backed off. Lister specs. I believe state 4 to 6 thou. at one side, but I have observed that much gap at one side with no shells installed at all. Finish of parting faces on roids can be wildly rough.
I have also seen pinched clearance at the sides with much too much clearance top and bottom. One of the symptoms of too much crush is metal distortion near the ends of the shell. Also seen protusion of several thou. which would be good except there was two thou. short of ANY clearance. Shimming that away four thou. would result in several thou. less than ZERO  crush or nip!

The design Veggie shows uses a different mechanism to locate the shells than the other more common roids and Listers but still MUST have a controlled amount of crush when installed and torqued as Bob mentions for heat transfer and friction. Those bits of tabs or the tip of the slinger protrusion into the lower shell is not a substitute for proper bearing crush.

It is hard to get a handle on the issues when many people have seen such a variety of parts and machining and damn few exacting measurements.

[playdiesel]

It is hard to get a handle on the issues when many people have seen such a variety of parts and machining and damn few exacting measurements.

Exactly

[mobile_bob]

probably all the more reason to start from square one, tear it down and start measuring
everything so you know what you have, and what is needed to get it right.

bob g

[veggie]

*** UPDATE ***

Tonight I got a bit of time to investigate further.
As suggested by some very wise members, I removed the head, piston, and connecting rod for closer inspection.

I found some interesting things....
First I'll discuss the rod clearance.

The rod itself seems to be first class.
Excellent forging and good machining finish.
With the con rod on the bench I installed the suspect bearings (which were overhanging the mating faces) and torqued up the bolts.
The excess nip left a gap between the con rod caps.
I tried to capture it in the attached pictures.

Tomorrow I will take the con rod to work where we have an inside micrometer and do some measuring as I file the shell ends.
However, it looks like a bearing shell nip problem to me. If the gap in the bearing cap were removed, the resulting clearance may be just right.

I will post a few of my other findings as a separate thread (different subject).

veggie

[vdubnut62]

Ron, What expactly is wrong with Veggies engine is conjecture until he measures. My experinace with Indian clones is very limited but I am a little experianced with what is properly known as non-precision bearing bores. If the insert is over sized for the bore of the rod, which is Veggie's problem, and the rod is tightened three things can happen. 1.The bearing metal is pushed outward at the parting line giving the locked up condition you suggest. 2 The rod and or cap bends around the inserts to touch at the outer edges.  and 3 Assembly torque is reached before either 1 or 2 is reached. or 4. SOme combination of 1-3.  None of the above will cause low clearance where we normaly measure things with plastigauge, at the middle of the cap. Pinch, if it occurs will near the parting lines. Basicaly the weakest part gives when you have more crush or nip than you should have and believe it or not it usualy isnt the bearing insert. The rod and cap wil usualy bend to meet or never meet at all at torque.. An experiance asembler can detect these problems as it will come up to torque slowly or "spongy assembly" is often used. The original Lister manual tells you to check for crush or nip by torqueing the cap then loosen one bolt and measure how far the rod opens up on the off side. I think it says .004 is correct but dont quote me on that. If I had similar parts and ten minutes in the shop I could show it to you'all lots easier than trying to explain it here, sorry.

No, I follow what you are saying, A little surprised though that the cap would give that much.
Ya'll Preach on, I'm listening.
Ron

[veggie]

This one shows it a bit better.
You can see the bearing shells are in contact but the cap is not seated.

veggie

[veggie]

Here's the CHP system construction, now on hold until I get the bearings repaired.

veggie

[rl71459]

Very Nice System.  Nice work!

[veggie]

*** UPDATE ***

This info may be useful to GM90 owners...

As a follow up, it seems that the rod shells for GM90's are meant to be "fit" by the user each time they are changed.

I opened several boxes of replacement bearings and they all sit slightly higher than the rod cap mating surface.
The protrusion is then filed down to the correct Nip and it seems to result a correct bearing clearance.
The con rod caps do not use shims.
The nip value is a trail and error process. File the bearing, bolt on the rod caps, measure the clearance.
File a bit more, bolt on the rod caps, measure the clearance. etc...

Cause of my Failure:
In my case, the highly skilled technician at the factory omitted the filing process and bolted up the rod cap with a 10 - 12 thou. gap
in the bearing caps causing a noticeable knock.

Thanks everyone for your suggestions and help in solving this.

veggie

[Zero_G]

I just inspected the rod bearings on my new 6/1 "kit". It came with 2 shims on one side and 1 shim on the other. I took the shells and shims out and the hole was not round. I then installed the shims and, bingo, it was round! I reinstalled the assembled rod to the crank using plastigage and it came out as .006". I can live with that.

My dipper was bent to increase the clearance, so I took the opportunity to straighten it out and grind a little off the bottom.

I need to check the piston/head clearance next.