start We have received a couple pictures of the condition of our rods we sent out to be straightened. All 4 were bent to some degree. This is the 1915 T that had the knock in the newly rebuilt engine. They also cleaned up the sharp edges of babbit at the sides of the caps. This excess material would have just broken off over time and fell into engine, I believe. The rods are on there way back home today. Will let you know how things go when rods are reinstalled. Picture 3 shows the before and after of the cleaned up babbit. One on left is after, right is before. Bob & Ricky
For some reason I can't upload another picture of the babbit issue. Bob
Here it is. Bob
Thanks for the update. I suspected they were bent. Just to reinforce what was discussed before. Support the piston from the wrist pin, when tightening the wrist pin bolts. Treat those rods like they are as strong as a "wet noodle". Looking forward to hearing how the engine does for you after the rods are straight ....
What was the off set reading on your rods, I don't see anything on that.
That is just as important as twist, and bend.
Herm I'm curious mind you, how do you check the offset? It is more than a function of center to center isn't it? I see the two directions bent on the one shown. Do you have a photo of checking offset? I understand the direction you're talking about, just not sure how one would check it. Thanks.
Wow, that's a NICE fixture they used! Pays to send stuff to folks who have the right equipment!
If all my rods are tracking dead center on the crank, the distance off center that they are tracking on the wrist pin I believe is the offset. What is the tolerance allowed for the offset. All 4 of my rods have a slight "S" bend in them but not enough to worry about. Bob
Herm I'm curious mind you, how do you check the offset? It is more than a function of center to center isn't it? I see the two directions bent on the one shown. Do you have a photo of checking offset? I understand the direction you're talking about, just not sure how one would check it. Thanks."END QUOTE"
These two pictures shows how far this rod was off, on off set.
This means that if the rod was installed in a cylinder, such as a model T, the rod would run true if twist and bend was Zero, but the rod would be that far off from center in the cylinder, and the wrist pin in some cases would stick into the cylinder wall, and groove it.
The rod is checked by sliding the rod over to one side in the rod aligner and setting a small shaft to the thrust of one side of the rod, and then turning the rod around and you can see how far the rod is to being center.
90% of rods need the off set adjusted. Some are as high a 1/4 inch off.
The width of the wrist pin bore has to be dead center of the width of the crank pin end of the rod, same amount of metal on both sides.That would be called Zero off set.
Some rods in other cars are made with off sets like 3/16's,and more, that you also have to set, or you have the same problem.
If I ever have the extra money I'm getting Herm to build me an engine!!
Herm, Is it not true that when the wrist pin bolt is installed in the notch in the wrist pin, it's impossible for the wrist pin to extend beyond the sides of the piston? How can it gouge the wall? I'm a little confused. Bob
If all my rods are tracking dead center on the crank, the distance off center that they are tracking on the wrist pin I believe is the offset. What is the tolerance allowed for the offset. All 4 of my rods have a slight "S" bend in them but not enough to worry about. Bob"END QUOTE"
The tolerance allowed for the offset is always Zero. It is either right, or wrong.
The "S" curve in the rods won't hurt if they are straight, but what made them that way was the points to keep the rods from doing that was not followed. The bending points were not chosen right.
You can check your off set by putting a wrist pin in a rod, and then put the wrist pin in the vice, by clamping the ends of the wrist pins.
Have the vice turned so the crank pin is over the bench, and slide the rod on the wrist pin clear over to one vice jaw.
Now set something stable buy the rod thrust, just touching. Then turn the rod around and do the same thing on the other side.
If that is the same, your rod has no off set, and if there is any difference, that is your off set.
Herm, couldn't that test just be telling you also that all the difference is the thickness of the babbitt flange from side to side and slightly off setting the rod?
Herm, Is it not true that when the wrist pin bolt is installed in the notch in the wrist pin, it's impossible for the wrist pin to extend beyond the sides of the piston? How can it gouge the wall? I'm a little confused. Bob"END QUOTE"
OK, First I want to say that Dan Brown showed me about a year ago that some of the pistons now days Do NOT have the wrist pin bolt groove ground in the center of the piston pin, so when you tighten the bolt on the wrist pin, and as you slide the wrist pin to one side, one side does not come out of the piston, but the other side does.
Just something to watch for, or check.
If the crank is not centered on the center main in the block, it can happen. When the crank gets warmed up, and if it is not centered, it will take all the rods to the pin bosses.
If the rod has off set in the rod, it can happen.
I am not saying you have any of this Bob, but it should be checked.
Herm, couldn't that test just be telling you also that all the difference is the thickness of the babbitt flange from side to side and slightly off setting the rod?"END QUOTE"
Yes, that is what off set is, and you don't want any.
Yes, that would change the off set if good or bad, by removing babbitt, but if it took to much, you will hear it run.
The rods should be measured to width of 1.500 from flange to flange right under the web. If to much?
There is one thing I keep forgetting to put in the posts.
How do rods get bent.
They DO NOT get bent in an engine, The rod builder when machining, will machine the rod, and then check for alignment and finish what the rod machine couldn't do.
The problem is very few builders even have a rod aligner, or knows what to do with one.
The other ways have been talked about here on other posts by the Guys.
Thanks Herm for the explanation and the offset picture.
Sorry Herm, I don't really share your concern on the off set being zero on a T engine, doing the maths on Ford specs, the shaft couldn't grow to exceed the clearances of the rod to piston boss, unless a cast piston and the brass bushing is pressed in to fare, with an aluminium piston, the flange on the babbitt would have to be at least 1/16" off set, + a shaft growth of 1/32" before it even would touch.
I don't know where your getting that information, but it wasn't from me.
Can't read a post either, AAAAAA
Many off sets are as much as a 1/4 inch on some Model T rods, with the majority, 1/8th to 3/16's out.
Frank, with lack of engine building experience, you will never get it, and I don't really think you would care, or bother to change it, just throw your motor together, and say all Model T motors make noise, don't they.
Take a picture of all your rod alignment tools you said you had, I would like to see them?
Interesting ruler you use Herm, as much as a 1/4".
A bare rod width of 1-3/8" and with babbitt 1-1/2"
Just to humor you Herm.
I use the mandrel method with no problems at all.
Wow, Frank, with a set up like that, pictures and everything, customers should be running over each other to get their rods aligned.
Yep Herm pretty simple hey, don't need to make it out to be rocket science and mega dollar tooling to get the same results!
Frank, I still think you are two Rockets, and 3 dimes short of the same results.
It's good to have a laugh before bed time, you still true to form, things can only be done right by the Herminator! for you to make mockory of the mandrel way is saying that Henry Ford didn't know what he was doing, check the Ford service book.
I'm afraid to update you guys as to how our engine job turns out after we have our rods straightened. As to if the knock is gone or is still there. I'm sure glad you 2 guys live in different parts of the world. I don't think Australia or the USA would be big enough for both of you. Would you like to know who is straightening my rods? I'm leaving the offset correction until last even though it is minor. We plan on heating the rods to just below the melting point of the babbit, then quench them in Kerosene. They will straighten to zero on there own. This procedure only works on the offset. The dancing (bend & twist) of the rod still has to be done as described by Herm & Frank. I can't put my hands on the book I got that little secret from right now. Bob
You make with the Joke, right?
Had to say something to get this thread back on track. The heating and kerosene was a joke. No one has said anything about measuring the distance between the two journals of the rods. Is this not critical on model T's? I've seen sets of rods out as much as .025" Bob
Here's the update on the engine knock. We received our pistons back from the straightener and they looked great. We installed them and set the clearance on the crank to 0015. Remember to start with, when we shorted out the 3 piston the knock stopped almost completely. The #3 piston was the one bent the worst even though all 4 needed straightened. We closed up the engine and started the car. Different knock and louder. Now it took shorting out #2 & 3 to stop the knocking. We were told that the center main would knock if it was more than .006. We checked the main and it was a heavy .007. Remember, this motor was rebuilt a year ago with about 1500 miles on it. We closed up the clearance on the main bearing to .0015 and before replacing the pan, we slid a piece of thin cardboard up between the cam and the connecting rods and cranked the motor slowly. One piston cut the paper. The rod bolt head was touching the cam shaft. We then discovered that the engine rebuilder had ground the cam side rod bolt heads off 0n an angle for clearance and we had one of the unground bolts installed on the wrong side. Correcting this and replacing the cover, the engine runs like a new machine finally.
A lot of sleep and prayer went into this hunt to eliminate a knocking motor. Thanks for all the good advice and comments. Ricky and I are still best of friends and I hope this thread hasn't caused any of you to have a falling out. Bob & Ricky
Very interesting, glad you got to the bottom of it, thanks for the update!
------ Warning, newbie questions below --------
Are you running a stroker crank? What cam are you running? Is it advanced from the standard Ford position?
Question for the rebuilders - Is it common to have to chamfer the rod bolt heads on the camshaft side for clearance?
All the genuine bolts had chamfers, maybe the ones that didn't are ring ins.
Mark, The cam is a 280. head & crank are stock. High rise aluminum pistons.
Frank, The rod rebuilder said the bolts were not original Ford bolts but did have some chamfer on them and he could see where the engine rebuilder had ground the heads for additional clearance. Bob
If you had .007 " clearance in the center main and removed shims from the main cap to reduce the clearance that would put the center main of the crank shaft out of alignment. This misalignment causes the crank to be stressed and the stresses go through a reversal where they are first in compression then in tension for each revolution of the crank shaft. This type of stress is the leading cause of crank shaft breakage especially when the crank shaft breaks at the number 1 or 2 rod journal.
What Art described in the previous post is exactly what happened to my '14.
Just before I bought the car, the center main was adjusted causing the stress on the crankshaft Art described. Sure enough, after maybe 1 to 2,000 miles, the crank broke between #1 and #2 rod journal.
So what's the answer for this? Take the engine out and check the main bearing alignment. You will probably have to pour new main bearings & line bore them so the crankshaft runs true.
I welcome other comments on this. Herm - any comments?
Bob - to add a bit to Art and Keith's post, and to them and many other Model "T" "engine guys", please correct me if I'm wrong, but here's what I believe is the reasoning behind the center main bearing condition that Art & Keith are describing:
Strange as it may seem, while the front and rear main bearings tend to wear on the bottom (in other words, the babbitt in the bearing caps) partly from the weight of the flywheel especially in the case of the rear main, the center main tends to wear the babbitt more in the TOP half of the bearing,...in other words the babbitt in the engine block portion of the bearing wears in trying to prevent this crankshaft bending upwards. This is because the crankshaft would tend to bend upwards in the center, except for the top of the center main preventing such bending, and this is the "misalignment" that Art Wilson was talking about. It is interesting that the weight of an unsupported auxiliary transmission (more weight, tending to try to "bend" the crankshaft and thus wear the TOP of the center main bearing babbitt) actually worsens this wearing of the top of the center main bearing. If it helps, think of a door with three hinges, and the center hinge slightly out of alignment with the other two hinges.
Anyway, if you took out a shim in the center main, or slightly filed the cap, you actually bent the crankshaft slightly upwards when you tightened the center main bearing bolts, and this causes the crankshaft to actually bend a couple thousandths with each revolution. This is the "stress" and "misalignment that Art and Keith were talking about. Also, this is why "line boring" or "align boring" (whatever is correct) is so important as it "aligns" the main bearing bores perfectly with each other as well as boring them to the perfect diameter for proper bearing clearance.
Sorry to be so "wordy" but not easy to explain briefly,....hope this helps,.....harold
I found out about this center main bearing issue the hard way.
Before I bought the '14, it probably had a knock and the owner took it to someone to have the cause of the knock fixed, but didn't want to spend any more than necessary as he was going to sell the car. So the quick fix is to just adjust the center main bearing by taking out shims or filing the bearing cap until the play on the center main bearing is removed and the engine runs quietly.
How can you avoid buying a car that has this center main bearing issue? Ask the seller if any engine work was done on it recently, find out what was done and who did it. Hopefully see the paperwork for the work done. And hope and pray that the seller is honest.
Sometimes the center main was taken up 1 or 2 thousands several years ago and the car was not driven much. Further, if the car has changed hands more than once, the current seller may not even know about a center main issue.
Sometimes you get one with a good engine and sometimes you don't, that's just the way it is.
Keith, you and Art are right.
It can't come out any other way if run for very long.
No matter how many shims that were in it when the last babbitt pour was, after .006 thousandths are taken out, of all 3 mains, or just one, it is ready for a babbitt job.
If the front and rear have most of the .006 thousandths, and only the center main is adjusted that much, the main will whip and keep pushing oil out of the way, and as you guys said stress the crank greatly, and will also push babbitt out very fast.
The Model A engines are known for taking out the center main when run at a high speed. I read in a Model A magazine years ago that the reason is due to the center main supporting 2 sets of connecting rods and pistons both going in the same direction, and at high speed the inertial forces from the pistons and rods become great enough to overload the bearing. I'm not sure but if I remember correctly the article said the load is something like having two 70 pound cannon balls bouncing up and down on the shaft at speed.
Herm brought up a very good point about the center main whipping and pushing the oil out of the way due to load reversal, which would greatly accelerate the center bearing wear and failure.
Harold mentioned that the center main wears more on the top side. Very interesting. A guess is that possibly with the up and down whipping action of the crank, the oil is more easily pushed out of the top side where the longitudinal oil grove is located than on the bottom where there is a continuous bearing surface.
Herm, What are your thoughts about minimizing or eliminating the oil feed groove on the center main and machining a trough in the block above the oil feed hole for the center main to maximize the oil supply to the bearing. That would give much more uninterrupted bearing surface on the top side of the bearing and could reduce the amount of oil that gets pushed out from the whipping action of the crank.
Art, in my opinion, the Model T's never had enough oil grooves. A spreader groove does not do much.
I use the Model A pattern of oil wells, and oil grooves, in the Model T's.
To tell the truth, I have never seen to much trouble with Model T's with the center mains. The first, and center mains normally wore .005 to .006 thousandths, and the rear.030, or a little less if the crank shows much wear.
But the Model A's, the center main is the bad one, as the heavy flywheel has no support, it just hangs out there, bowing the crank.
Gentlemen, Although this is a 15 T, it has a 25 engine. Does this 25 engine give us any more ray of hope over the original 15 engine when addressing the work we did to the center main bearing? Bob/Ricky
Another question. What if I went back into the center main and loosened up the clearance to about .0045? It was at .007 and I closed it to .002-. I guess I'm looking for any solution besides pulling the motor and redoing the mains. I'd like to get this season out of it and pull it next winter. In your opinion, would I be better with the looser main at this time? I'm assuming it shouldn't knock at .0045? Bob
Bob, the center main issue brings up the point mentioned above. "It makes me question, everything the re-builder did" All of the points mentioned about stressing the crank, oil starvation, broken cranks, ect, are valid points. If you loosen the center bearing it may "buy a little time" but it is a big unknown. The crank may already be cracked. So it could be the engine is "living on borrowed time". In my way of thinking the only proper way to proceed is to do a "total" teardown, inspect every single part, and re assemble. You probably have a lot of useable parts such as your engine block, rods/pistons, cylinder bores, the cam, valves, and lifters are probably OK. And if lucky all the trans and magneto parts are OK. I would also have the pan/crankcase checked on a pan jig. So you may only need the bearings re-poured and the pan straightened. Sorry for not being able to give "good news" but in my opinion the center main issue is a very big issue. As a side note, I have rebuilt several "budget" engines thru the years. That is where we reused anything that was even marginal, such as reuse the pistons, hand grind the valves, pick used rods that had decent looking Babbitt and straighten them, use used cams and gears, we just put new bushings in the trans and reuse everything else, and even reuse the babbitt in the mains if there was any life left in it. But, the two things I always made sure of was straighten the pan/crankcase, and make sure the 3 mains were in perfect alignment. So far, every engine I have built is still running. I may just be lucky, but I feel like the straight pan and straight aligned mains, are the major factor. Good luck in whatever you decide. respectively submitted Donnie Brown