MTFCA Forum

[image][/image]I’m planning to run make a shim unless I hear different.

Picked up a project, pulled pan to give it all the once over and clean out the junk that made it into the block over the years.

Found the from con rod cap had a loose bolt. One one side, about 1/2 turn from snuggling up, I could wiggle it back and forth. Pulled the cap and the babbit looks like to may have wanted to wipe a bit in the past. Likely 20-30 years since it has ran. If I tighten both bolts I can turn the crank but it’s tight. Significantly more effort than with that bolt loose.

Do I cut a 10-15 thou shim and see if I can get the bolt right and engine free, leave the bolt kinda tight but not tight or just leave it loose as it was and check it out after some driving?

Time for a new rod

anything else will be a waste of valuable time

You need another rod, and the crank pin will need polished and carefully checked for out-of-round.

A new rod will not last on a flat or tapered crankpin.

If any babbit is smeared on the crankpin, it will probably cause damage to the replacement rod.

The other rods need checked for wear, damage or excess clearance.

If the rod babbits are well-worn, and if the crankshaft checks out good, I'd replace all 4 rods while I was messing with it. Check main bearing clearance and end play, and be sure pistons and rings and valves are in good condition.

Any used parts that are removed and put back in need to go back exactly as they were.

Did the rod in question have any shims under the cap? If not, that's not a good sign.

Normally a loose rod that still has good babbit is adjusted (tightened) by removing a shim or two, not by adding shims. The same is true for main bearings.

Just so I’m clear. A rod bolt was loose, not the rod on the journal. No shims, if I tighten this bolt it will tighten on the journal to where you cannot turn the engine. It seems that if it HAD a shim and a tight bolt all would be fine? It would have some oil clearance and the bolt tight.

Journal looks good, nothing on it.

I’m trying to resurrect a parts/farm/junk car into at least a running moving chassis. I’m not going to go through an entire rebuild at this time. That’s a pit I’m not jumping into for this unit.

Robert,
If you just want to get it to run you could use Timesaver to fit the rod bearing to the crank.

Robert,

It's sometimes hard to figure out what people have done to vehicles, and why, but I suppose one could make some guesses in this case ... if it were me I'd certainly shim it appropriately and see how it went.

FWIW it's my view that Model T's have, collectively, done millions of miles with all sorts of things awry with them, yet they still seemed to work relatively well. The engine is low-revving and lowly stressed and although there are certain well known things that break I think that as long as the babbit is reasonable secure, the cap and rod aren't cracked, and the journal isn't too out of round there's no reason to expect any particular issue, although I'd probably drop the pan and check again after a while.

Luke.

that cap and likely the rod ran and wobbled back and forth so much that most of the 1/2 cylindrical bearing surface is gone and you are left with an hourglass shape with barely any bearing surface left. Looking at your one picture, the babbit is so worn out at the ends that even if you lapped it to fit, you could not finish it off perfectly (enough) to the point of having sufficient bearing surface. That is important if you expect a hydro-dynamic non-contact bearing when operating. You might get it to run quietly (if you're lucky!), but it won't last for long.

It's your car and you're going to do what you want with it, but most folks who sell their ailing car in disgust inevitably have been found to have spent their hobby time performing a series of "fixes" like this and end up declaring the vehicle is "junk". I just don't wish to see you become one of those guys.

Really, reading this, it seems you're asking for permissions to throw in a shim, and not seeking advice, (how do I xxxxxxx? is nowhere in your posts) so if I am correct, you don't need anyone's permission - it's your car

good luck

Going by the % of surface contact on the smear, I'd say the reason on one bolt being left a little loose is that the cap, A, is fitted 180 degrees out or, B, the cap doesn't belong to that rod. They are machined to be a match and not interchangeable.

Perhaps someone in the past decided that the rod was loose and took out too many shims and wiped the bearing. That could explain the loose rod cap and the appearance of the bearing.

I'd be concerned about damaging, or further damaging, the crankshaft, by trying to run that rod, even for a short time.

Thank you all for the comments.

I’ll work on getting journal measurements and go from there.

I just replaced a single rod in my engine. FWIW the replacement re-babbited rod made to fit my crankshaft was NOT the same shape or weight as the one I removed. I was concerned about balance and ended up returning the new rod and had my original rod re-babbited and bored to fit my crank. Then I used timesaver to lap it to a near perfect fit.

Robert:
a connecting rod or main bearing should be shimmed and bolts tightened and castle nuts cotter pinned ... the bearing clearance is NOT adjusted by how tight or loose the bolts are ... you may be successful in the short term by shimming to achieve a slight drag on the bearing journal with the rod bolts tightened ... for an engine that will only see limited use this may be acceptable ... always an optimist ...Gene French

The rod may have become very loose, perhaps due to a clogged oil line or low oil level, and maybe someone took all the shims out in hope of "getting by". If the rod was still loose, the hammering might well have loosened the rod bolt, especially if it was not pinned. In any case, the rod is not fit for further service without repair, and the crank pin may not be. The rod bearing has been severely abused, that's for sure.

Hi Robert,
If your rod jurnal is round & the other rods look OK I would look at the possabillity that the cap has been installed backyards ( happenend to me)
If you have modern pistons changing the rod is possible with the head on. If you have stock pistons it can be done but the amount of profanity is
not worth the cost of a head gasket. Time saver is your freind in this situation but if you have stock pistons it will be a lot of work. What the rod
looks like is very important also. In ran a out of round crank for 7 years ( lots of work keeping it from knocking) but it got me to the point that i
could biuld an other engine to install so I could redo the original one.
Craig.

"Do I cut a 10-15 thou shim and see if I can get the bolt right and engine free, leave the bolt kinda tight but not tight or just leave it loose as it was and check it out after some driving?"
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Clearly here, there are more immediate concerns, pretty well covered by others already. However, a couple things I would comment upon.

With tired abused and messed up old engines, anything more than just wasting some time to see how far you can make it go on minimum effort requires some degree of precision!
Whether poured Babbitt or insert bearings, the contact surface should be more than eighty percent of the total bearing surface, and about ninety-eight percent of the heavier stress areas in line with the cylinder. That much area must be within a one thousandths inch of perfection! Just a few high spots with a couple thousandths inch extra height may bind the bearing enough to keep the engine from turning enough to be started? Too much low area will cause the bearing to hammer out and crack, and eventually (and likely quickly!) fail totally.

Unless discussing the total amount of shim used? One never speaks of engine bearing shims in the "10-15thou" range. Final fitting of a model T's Babbitt bearings is almost always done with one final more or less "one thousandth inch" shim! Sometimes, and I have done this several times myself when I could get a few, the final fit is one more or less "one half thousandths" shim! Or, alternatively, a couple more "draws on the rod cap with a sharp very flat file.

Rod bolts should never ever be run loose! In truth, really early engines often did that by design. However, they were not intended to ever exceed about 300 rpm. The bolts being loose was how the bearing tightness was adjusted back in the early days. When rpm began to exceed about 500, it quickly became obvious that loose bolts on rod or main caps was NOT going to work for very long.
If rod cap bolts are not really tight, like nearly twenty foot-pounds tight, they WILL while running begin to shift about and work all connecting points in terrible ways. Flat surfaces, holes, bolts and nuts themselves, all will begin to be beaten and worn and become even more loose very quickly. Bolts WILL stretch! And then the Babbitt begins to hammer itself onto the journals.

Since I have almost always had to work with a tight budget, I have very rarely had an engine rebuilt by anyone else. Most of my model T (and even some newer vehicles?) engines I have reworked myself. Several of them I have gotten a lot of miles out of with no troubles after I reworked them.
For my model Ts, I find good looking used rods, mix and match styles and weights, then hand fit bluing and scraping the bearings. Then I use a balance scale that I made myself to balance the rods and pistons. Starting with an engine that isn't worn out, one can get a really great engine that way. If one makes the effort to properly fit everything.

....... "If one makes the effort to properly fit everything".....


Exactly.

Precisely.

If you are just trying to get it going to see if it runs, add a 1-2 thousandths Shim under the tight side and try the same or a little more on the loose side and put a piece of plasti-gauge across the bearing surface and tighten it down and then pull it back off and check it. Play with it with shims until you get about 1 to 1 1/2 thousandths clearance.⁶ Clean off the plasti-gauge and coat it with white lubriplate and give it a try.

A piece of leather belt , harness leather soaked in oil or bacon Rhine has been used as a substitute bearing many times in years past, so if you have quite a bit of babbitt left You might want to give it a try as you have a bearing,just adjust it and give it a try.
A lot of people think I do things in a crude or prehistoric way but when I work on my projects I do it my way. That is a good way to learn.