How do I fix a rod cap where most of the babbitt has chipped off the shoulder? IT is only on one side.
Should I or could I replace the rod and cap with one from a vendor?
Can you get a picture of the parts. Easier to advise if it can be seen.
If one is bad now, the rest can't be be far from it. Herm K is the man to speak to for Rod work. He is on here as often as most of us.
That rod has served it tour of duty. It is time for a replacement. The others can't be far behind.
Do you mean I should replace the rod cap?
Or should I replace the rod and cap?
It will not be as simple as replacing a cap unless you are just building up a junker engine for around the block use.
First you need to measure the crank journal to get the right size rod, rods do as a rule come in a set of 4 to be of all the same weight, then there's the issue of how good are the mains and crack testing, bore, valves and the list will grow, magneto, transmission etc. If you are looking for a reliable touring T it might be time for a full rebuild.
you need to check the crankshaft for roundness and taper. If it is still round, you can get a set of rods poured and bored to fit the size of the crankshaft in thousandths of an inch. If it is out of round you need to replace the crankshaft or regrind it if it is not cracked. Usually the major wear is on the rod rather than the cap, so check the rod also and the other 3 rods. Replacement would take a complete rebuild of the engine. Frank is right.
At the very least, you're looking at exchanging your 4 rods for re-conditioned rods, but you need to know the exact size of your crank. Usually, if the rods look like that, the mains are just as bad, as are the lifters, valve guides and everything else...just sayin'. If it's a stationary engine running a sawmill, that's one thing. If you're gonna drive it, that's another.
Good advice, All!
Check your other rods. If your journals are more than 0.002 out of round, or tapered then the rods will run ok if properly fitted but they will not stay in adjustment and will require frequent refitting. They other three rods may be just fine. If they are good,then mike the journals and take up any slack. Assuming the other three rods are good then replace the bad one with a new rod and fit it to the journal.
You will not be the first one on the planet to replace just one worn rod and put it back together.
Model T crank pins, should not be more then a .000-50 out, any more and the crank eats away at the bearing.
If a crank pin has taper, there is no way to fit a New rod. The rod will ride on the high spot on one side, until it wears its self to the other side, and what ever the amount was in thousandths, is now, the clearance, Plus the taper clearance.
Because the middle of the rod, and the middle of the cap will be smaller, along with the crank pin in Diameter, the sides being larger in diameter, so when the pin opens up the clearance, on top and bottom of the rod, from the sides of the pins being larger, what ever the rod needs in clearance it will open up to and will keep going.
Keeping rods in adjustment like this, is impossible. Hammering rods can also crystallize a crank pin.
On a .002 thousandths flat crank, the up and down would be at least .004 clearance.
Also the largest part of the crank pin, which is the side of the pin, as it moves its self forward in the bearing, squeezes out the oil in front of it, and the smallest part of the crank pin, which is top and bottom, get cheated on oil.
In the picture, above, the Babbitt was a cold pour, and or the tin burnt off on top from improper heat. I can see, only a little tinning on the radius.
If the others are from the same set, that would remove any confidents I would have.
First, thing is to check the crank pins .
Actually Herm, and this is not to start an argument but some facts, Ford allows up to 2 thou out of round on the big ends and oil to bearing tests state that the oil wedge works it's maximum pressure with an 1-1/2 thou out of round pin.
Frank, More than that! The 1924 FORD service bulletin says .0025Ē out of round was acceptable!
Frank, no bearing will last that way, not even oil pressure. If it works for you, do it. LOL It would be better if there was a LITTLE common sense with your thinking.
.002 thousandths out of round, There is no way to keep a .002 thousandths flat crank at the fit it will last at.
When I was in my teens, I bought a 1921 center door. The rods were .001-25 flat, and I would adjust them every Sunday morning, and we would drive for the after Noon. When we would get home they were knocking again, so next Sunday morning, we would have a rerun of wagon train, and do the same old thing if I wanted to take the T.
It took me a while, but I found in the K.R. Wilson Tool Book, what he says about it.
If any body has got the book, it is on page 10.
If you don't, I have taken pictures, overlapped, if you can read the printing. They may not be large enough to read.
Herm, you try to to imply it's my way of thinking, not so, like Adam has posted, it's in the Ford service bulletins and manuals!
Herm, I did post that I didn't need a argument out of this, but lets look at some of the facts.
First off, yes I agree with you on a perfect round pin but there is a difference in reconditioning and re-building.
Engine specs for reconditioning brings every thing back to zero hours.
Re-building, manufactures give specs that are still with in serviceable specs.
Even by modern specs on Automotive Engine Re-conditioning/crank shaft grinding, remember that they are not engines that have thrown all the rods but just plum wore out and still running.
Frank, your first, and last Paragraph says it all about the post I made.
They are NOT talking about .003 thousandths, flat. They are talking about a shaft with normal wear, that is still round.
Wilson said you could not go any more under then .006 thousandths. This is on Rods ONLY, and NOT flat.
Frank, and all, read the first, and last sentence, in Franks Paragraph. It says the same thing, the shaft has to be ROUND.
Frankie, you are the one that has trouble reading, as you always accuse me of.
Frank, thanks for making my point.
Plain as day Herm, .002" out of round!~!
Herm, I did agree with you 0 is best! but these old babbitt bearing engine designs have more tolerance in run out specs than a higher revving more modern engine.
And just to show that Fords specs are not a typo, Chev specs are .002" out of round specs as well.
I don't mean to discourage the original poster... But judging by the condition of the babbit in that cap, no matter how out of round the crank pins may be, any rebabbited rod will outlast the rest of that motor.
Many of us have pulled apart old motors with babbit that looked just like that, only to find that the rest of the motor is just as bad. I'm talkin bout flat cams, 2 piece valves so sharp you could shave with em, rusted out valve seats, lifters with pockets worn into the top, wore out timing gears, burned up clutch packs, rotten band linings, loose magneto magnets, ring gear missing teeth, cracked transmission drums, and bent pans. Not to mention all the critters that somehow find a way to build a home in there, and are kind enough to leave behind their outhouse!
I think we can all agree with the theory... If the machine work is done more accurately, the life expectancy of the motor should be prolonged. But nobody is doing machine work in this situation!? And nobody is suggesting that these roundness tolerances are acceptable in a rebuilt motor!? So bicker all you want... But why bicker over a band aid...?
Some time, some place, it would save somebody a lot of grief.
Also, you can straighten a crank, but it will never be straight enough to use with out grinding.
It wouldn't even work in a new Align Bored engine.
That is where most of the broken cranks come from. Either the crankcase, or a crank out of Alignment. They flex at every revolution until that spot crystallizes, and the crank breaks.
If the crankcase proves to be straight, then you can always trace it back to out of Align Bearings, or bent or warped, main shaft.
A flywheel bolted to a warped crank flange will also break cranks. Many times will take off the rear flange.
Regardless of what Ford publications say, .002 out of round will not be kind to babbitt. It seems that T engines like to make their own bearing clearance. Meaning, even if you set up a motor with snug bearings, through use, the bearings will tend to settle in at .0010/.0015 clearance. If we take the case of a .002 out of round crank, with rod bearings fit snug, we must recognize that the bearing is only snug on the high points of crank journal. Over the low points, we have .002 clearance. If we then take my first comments into consideration, the high point areas will settle in with about .0015 clearance, BUT the low points will now have .0035, or more, clearance. And, it's on those low points that the most force is exerted, (that's how they got low). At .0035+, it will start to knock. Maybe you won't hear it yet, but the babbitt will feel it and the clearance will continue to grow. I think the fact that the crank is out .002, and the bearing cap looks the way it does, kind of bears this out.
Even if we take the Ford specs to heart, do you want an engine operating at the extreme end of what's considered usable? Consider too, that when those specs were written, the speeds that most of these cars travelled at was about 20 MPH.
why didn't you post that before now, Jerry, it would have saved me a lot of typing!
I wanted to give you a good chance first.
Agreed Jerry, but this thread was started and answered to what Steve could get away with on a worn engine.
And Herm would save a lot of typing if he would bend a little and didn't try to have a new engine in every one's T.
He can still have his worn engine. I just wanted him to know what the possible outcome might be if he went that route. An informed decision, as it were.
Also, I too find it difficult to encourage anyone to do what I would not do in my own car. And yes, I do "get away with" lots of "comprises" in my own T's. I just wouldn't do this one...
Yes it is at an extreme spec but let me ask you this, because we would have a lot of measurements in-between, If Steve's crank comes in at a touch over the 1/2 thou out of round, would you consider it a right off or unsuitable for service like Herm suggests.
Let's muddy the water a little bit. Lets take a good mill file and shave off the high side of the crank 0.002. Now we have a round crank and can fit a new rod satisfactorially.
I have used a crank .0005 out of round with no problems.
If I were going to do that, I believe I would use some emery paper and a load of patience, not a mill file.
This is from an original 1936-1948 Lincoln engine rebuilding manual published by Ford Motor Company. This is good food for thought... Ford realized that they specifically had to point out the difference so mechanics & customers potentially didnít expect the repair to last as long as the new assembly.