Car is a 1915 touring with an engine knock. Knocking since new engine rebuild by professional. (So to speak) Shorted out plugs and determined noise was at the 3 piston. Tightened up rod to crank bearing .015 as described in manual. Started engine and knock is worst. Pulled cover again and determined rod at wristpin is hitting inside of piston when turned over by crank but only if spark plug is left in. With plug out, just comes close but not hitting. I'm thinking I have a bent rod????? Plan on pulling piston and rod after removing head to see if I have a contact mark inside piston. Plan on replacing all 4 rod's if one is bad????? Do I need to replace rings since rebuild was only a year ago? I have aluminum high compression pistons. Any pointers or recommendation appreciated. Bob

Get a machine shop to check the rods and replace only the bent rods.
The rod bearing clearance on the crank should be .0015. Not .015.

Can you not contact the rebuilder and see if he will warrant his work?

You can check the rods your self, it's not rocket science.

Bob and I are doing this together. The rod and wrist pin are moving front to back, front to back inside the piston as the engine is being turned by hand. Does this indicate that the rod is twisted? It moves on every rotation of the engine far enough to hit the inside of the piston. We have an engine knock that has been her since a rebuild one year ago. Have already taken up rod bearings.

If it were mine, I would examine all 4 by rotating the crankshaft. If the others are not knocking, leave them alone and just fix the one which is bent. This is what happens. The top of the rod is at a slant and when the rod goes up, it pushes the rod to the high side and when it goes down, it moves to the lower side. This condition would not cause any serious problem unless the wrist pin is scraping the inside of the cylinder wall. You can remove the one piston and rod from the block and either replace the rod or straighten it. If the babbit is still good straightening should fix your problem Whether or not you replace the rings, is up to you. You can if you want just replace the rings on that one piston. Or you can reuse the existing rings. You might get a little oil burning if you re-use them, but over time it should get better. They won't wear in as fast as they would if you installed new rings. I have reused rings which had little mileage without a noticeable problem. It is up to you.
Norm

Aaron, My mistake l left out a zero.

Hal, Rebuilder was contacted shortly after new motor was installed and knock was discovered. We were told to not worry about it. It should go away. All it has done is increased in noise.

I want to thank all of you for the response and advice. There will be a little something in the mailbox for each of you around the first of next month. Bob

Two other rods and wrist pins also move but don't knock. Should we fix all three or just the one?

Just re-hone the bore and your current rings will re-set. Make sure you get a good cross-hatch pattern to the honing and be sure to clean the area extremely well before reassembling the engine. I have never heard of a knock on freshly rebuilt engine of any type going away with continued use. I think you did the correct thing by tearing into it. Who knows what kind of damage this problems could have evolved into.

Richard and Bob. Since you say three of them are moving around, I would just start over and check and fix all four. Not being there and seeing the problem, it sounds to me like the rods were already bent and not checked on a jig, or the rebuilder bent them when loosening, or tightening, the wrist pin bolt. It is easy to bend them. If the babbit looks good, and the rings are fresh, and the bores of the cylinders are OK. and the crank journals are round and OK. and the wrist pins are tight. I would just have the rods straightened and reinstall them. Even if you were to buy new rods, you should have them checked before installing them. I always take a large screwdriver or drift pin that will slide thru the center of the wrist pin. Then clamp the end of the screwdriver or drift pin, in a vise. That way all the twisting of the tightening of the wrist pin is supported on the wrist pin and not the rod. Good luck and keep us posted.

If the rods were bent, they wouldn't move side to side, seems to me the problem may be with the crank, maybe. just an opinion, Dave

Is your rebuilder local? He should stand behind his work. His answer suggests either he doesn't know what he is doing or you might be getting a line of baloney.

You may be chasing the wrong problem , it could be your main bearings. You say the rods move back and forth against the piston, if you were to take a plastic mallet, could you tap them back. It would make a considerable difference in your diagnosis if they could be tapped back rather jammed up tight.

The center and rear main clearance can be easily checked. The front main will be a little more difficult. It could also be your timing gear.

In any case it's a disgusting pain in the rumpus.

It used to be that all good automotive machinist checked for bent rods in any engine that was rebuilt. Rods should always be checked for being bent before re pouring babbitt other wise you run into a whole nother set of problems. Not a lot of good auto machine shops left. KGB

"Pulled cover again and determined rod at wristpin is hitting inside of piston when turned over by crank but only if spark plug is left in. With plug out, just comes close but not hitting."

Any chance the piston is hitting the plug?? It should not unless high dome pistons are used or some types of high power heads. My question may be unnecessary as other comments still seem to indicate bent rods or miss-cut crankshaft.
Sort it out and good luck!
Drive carefully, and enjoy, W2

It takes the compression of the engine to make the rod and wrist pin move. I can't see that they are hitting anything. Also with the engine running, I can ground out #3 plug and the knock goes away.

Also on #3 and #4 the rod is no where near centered in the piston.

I would approach it as Donnie Brown suggests above.

As to having the rebuilder redoing it, since the individual did not have the know how to do this right the first time, and since he fails to acknowledge, or does not think, he made a mistake, his hands would be the last ones I would let ever touch my car again.

Bob.. answer this; When you short out no.3, did the knock go away??

If it did, then the knock has nothing to do with a bent anything.. it is possibly wrist pin slop, but along the direction of stroke and not the axis of the pin. But more than likely it is simply rod bearing clearance.

Put a small piece of newspaper that covers about 70% of the rod cap in place and tighten down the cap on the rod on the crank with the paper in place. If you can rotate the engine then it's still too loose. Keep grinding the cap face until the engine won't rotate with the newspaper in place but will when the cap is replaced WITHOUT the paper. It's old school but it works.

Are the rods in the proper way? W/the wrist pin clamp bolt on the camshaft side?

A bent rod will move side to side. That is a perfect indication of a bent or twisted rod. As to needing new rods. If the babbitt is good and the wrist pins are tight, re-use them. A rod does not care if it has kinks, twists, or shaped like a "Z" as long as the bottom bearing bore and the wrist pin orientation are correct to each other. That is where a rod alignment jig is a must. It can be done other ways but it is very hard to do and requires a lot of careful measuring and micrometer work, as well as a "known" test surface. Like I said before, Im not there and can not put my eyes and hands on the problem. But I would almost "bet the farm" that the rebuilder either did not check the rods or bent them later. Either way I agree with Jerry, He would not touch any of my stuff again ... Keep a working on it, It will all work out OK.

After giving this a lot of thought, there is one more thing that I thought of that could cause a rod to move back and forth. That would be miss aligned Main bearings. If your rebuilder re poured your mains and bored them some way to make them be out of alignment. For example lets say the center main is a few thousands to the left or right of a "true axis" of the other two mains, that would cause the crank to be moving in an eccentric path. If so the rod would want to "run" back and forth on the crank pin. That is a problem, that I can see no way to check with the motor in the car. Although an indication of that being a problem could be one or more of the main bearings showing a lot of wear or "excessive shine" on one side or the other of the bearings. It may not be that is the problem, and we sure hope it is not, but it is something to keep in mind ... Please correct me if my thinking on this is wrong. With all the work of the rebuilder being questionable I can see it happening. I was able to see what a bent rod could do on a friends car years ago. He had bent one rod while rebuilding his engine. It knocked very bad at idle on his first start up, So we pulled the inspection pan and were trying to figure out what was wrong. You could see the rod move back and forth while hand cranking it. I had him start the car while I laid under it and watched the rod. It jumped side to side and hammered like a jack hammer. Its amazing what that stuff looks like while running. It is a very violent world inside there. We only ran it for a few seconds but it sure changes your outlook as to what is really going on in there, when you get to watch it at "run speed". Anyway, we removed the one rod. I straightened it on my jig, put her back in there and the car is still going today.

All your rods will be out of alignment, If one is bent, they all are, because none were checked. even if they run quite, they can be way off.

If a rod builder tells you his machine bores them straight, he doesn't have to check them, just know, he has no clue.

Some day when I take the time, I will take a bunch of pictures on the process of rod alignment.

There are 3 steps to check, Twist, Bend, and off set, there is no one of the 3 steps more important, or less important then the other, they are all equal.

Rods can go in either way with the wrist pin, away or towards the cam, one is not any better then the other at all, but gives a reference to go back in if the rods and pistons have to be removed, but get them all the same. As Ken said towards the cam, as Ford did, is as good as any, but I install away from the cam and line with the piston slots.

There will be nothing wrong with your crank.

The reason for your frequent rod adjustment is the strain on the bearing, and rapid wear, in always bad alignment.

Use the old rods, if you get new ones they will have to be straightened also, unless the bearing is gone.

Lastly. the only way to tell rod alignment, is to check, you can't tell just by looking at a rod, when it is out, in the engine unless it is to the extreme. Rod alignment you want Zero run out, not just close.

Herm.

I think Herm hit it on the head (pun not intended), the rods were probably finish bored not quite in alignment. IMHO, after boring and fitting the big end, then the rods should be rechecked for alignment. You should be able to rotate the crank and the rod small ends should stay in the same place, fore and aft through 360 degrees of the crank. Anything else will shorten the life of the engine--and sometimes make noise too.
Hmm, anyone theorize that bent rods could hasten the two-piece crank syndrome? Just an idea that popped in (such ideas are oftentimes dangerous, if this one is, just ignore it!).

Crank should be centered on the center main to be right.

The front main should have ample clearance, on the rear as the center main, and the front of the crank gear should come to the same level as the front cover surface of the gasket surface on the block.

The rear main matters not, an you can have most of the babbitt thrust on either end, or anywhere in between.



1. picture shows, how to twist right, or left, by swiveling the top Jaw.

2. Picture, Bending of the rod, by top Jaw.

3. Two picture shows how far the off set on the rods hat has to be fixed, 95% of model T, A, and B rods are like that, not counting all the other brands.

Here is the latest update. We pulled the head and removed the piston and rod. We removed the rod from the piston, Just looking at the rod you can see its bent, I stood the rod on its crank end on a flat surface, slid the wrist pin back in the rod and measured up from the flat surface to the top of the pin. There is an 1/8" difference between the 2 sides. I then rotated the rod 180 and measured again. same reading, just reversed. When I inspected the piston, the wrist pin journal is a true slip fit on the pin. The outside of the piston is showing rub wear on the top area of one side of the piston and 180 on the other side the rub wear is at the lower portion of the piston. This tells me that due to the rod being tilted at the top was causing the piston to travel sidewise up and down within the cylinder.
This also caused the rod to slide over and slap the piston wrist pin journal on the up stroke. We are going to install a new rod and rings unless there is some one out there we can send this rod to and have it straightened????? The rods in 1& 2 don't move sideways at all. #4 moves slightly but is well within acceptability. Any comments. Bob

I think I would take lots of pictures and document, document, document! Keep all your receipts as well. At bare minimum your "rebuilder" should refund you a chunk of change to reimburse you for fixing what should have been done right the first time. If they refuse to do that, then it's off to small claims court. I had a body and fender guy who charged me for all new parts (and some of them were wrong and broken) to fix my truck after a deer hit. When confronted with the visual evidence he initially refused to give me a refund on the parts I replaced with the new GM parts I had initially paid for. So I dumped the used parts on the floor at his feet and told him I was off to file a case in small claims court. It was amazing how fast his tune changed after that, and I walked out a little wiser and with the refund I requested.

Bob -- You can send your rod to Ron's Machine Shop in Ohio and they can straighten it.

A rebuild from a year ago, at this end of the world it wouldn't make it to small claims, to many variables in why and how a rod can bend, water in the cyl, to much fuel, oil, to fare advanced, etc, etc, no proof that it wasn't straight when put together.

All I am interested in is getting my car back on the road. Don't want to get in to accusing anyone of any thing. Thanks for all the help.

"... no proof that it wasn't straight when put together."

You're kidding right?

Bob,

By the way you describe and recognize the trouble you're having, I'm confident that you could straighten the rod yourself. The actual straightening is the easy part. It's being able to inspect the result that's more important. If you have an accurate way to measure bend & twist then you've got it licked. At the very least, you couldn't make the one you've got any worse by trying.

Herm is correct above when he states that you at least have to check all 4 rods. Even the one that moves slightly but shows no other trouble will not last as long as it should. The bend will eventually wear at the babbitt and cause early failure.

Jerry, how would you or any one else know why it was or has bent, from supplier? or assembly? or as simple as that extra squirt of oil in the cylinder before the spark plugs screwed in, a hydraulic lock is all it takes.

And don't trust the flat surface of the rod bottom end (where the cap bolts on) as being a true surface; the Babbitt could be bored out crooked; this is why I recommended re-straightening (or at least checking) a rod after it's big end is fitted.

"... no proof that it wasn't straight when put together."END QUOTE"

You're kidding right?"END QUOTE"


That's what I thought , Jerry

Herm.

Jerry, how would you or any one else know why it was or has bent, from supplier? or assembly? or as simple as that extra squirt of oil in the cylinder before the spark plugs screwed in, a hydraulic lock is all it takes."END QUOTE"

Frank, give it up, this is way over your head!

Last time I heard, you still thought your mill bored them straight!

Herm, you have been preaching for years that the T con rods are always bent, twisted or out of wack in one way or another, now pray tell, with all your knowledge, how dose this this happen?
What you need to do is some research on reasons why con rods bend before you put your foot in your mouth once again.
You might have the end result to fix but not the reason why it happened.

Bob, by the first test, you showed an off set in the rod, by correcting the twist and bend, the off set, can go away, or get worse.

You can see that a rods web is not in a strait line, but it can also many times be as straight as a string, for alignment, with out extremes.

You can only tell if a rod is straight for twist, and bend by the inside of the wrist pin boss, and the inside if the crank surface, on the rod.

I will say again, the only reason a new rod will get out of alignment is first always from the machining operation, they are never straight, no machine will cut them that way, that why they make rod alignment machines.

Next when who ever takes the rod apart to install in the motor, they hold the rod to take the nuts loose, or tighten the wrist pin bolt, while holding the web of the rod in the vice.

Do your self a favor Bob, check, all the rods.

A word to the wise, where ever you send them, make sure that they do straighten rods, Many, many don't, or just make a stab at it.

I don't do these posts for any hidden reasons,
I am not looking for work, we are always full.

Herm.

Herm, you have been preaching for years that the T con rods are always bent, twisted or out of wack in one way or another, now pray tell, with all your knowledge, how dose this this happen?
What you need to do is some research on reasons why con rods bend before you put your foot in your mouth once again.
You might have the end result to fix but not the reason why it happened."END QUOTE"

You are so ill informed Frank.

Yep Herm, tomorrow I'm going to do 4 rods, 3 I'll make straight and the 4th I'll alter my settings .010" just so I can have a cock up like bob's engine and have the piston in the cocked position. Because it seems by you theory only human error can create a bent rod.

herm, i for one, always enjoy your input, please keep it up. the work photos you post are always on the money, thanks

Yep Herm, tomorrow I'm going to do 4 rods, 3 I'll make straight and the 4th I'll alter my settings .010" just so I can have a cock up like bob's engine and have the piston in the cocked position. Because it seems by you theory only human error can create a bent rod."END QUOTE "

Frank, if you do 4 rods tomorrow, they will all need alignment, but then you don't have a rod aligner , now do you?

That I do Herm, align and bending tooling.

Guys, I don't know what the issue is between Herm and Frank but it's making this thread to answer Bob's engine question rather nasty. Is this necessary??
From reading this thread, and thinking through how I would do things after years of being around machinery, I have concluded the following:
Given:
1)Rods get bent, they are actually somewhat fragile in this regard.
2)Even a straight rod when re-Babbitted can end up not being straight as the machining/sizing process can be off a little bit.
3) "Off a little bit" isn't a good thing, although the engine will still run, it causes undo wear and stress.
4) Mishandling the rod during assembly can bend/twist the rod.
As to #4, I would guess (and I could be wrong!) that the best way to loosen the rod caps would be to put the big end in a vise with wood faces, so as to not damage the Babbitt's edges, and not stress or bend the rod that clamping by the I beam section would do. When tightening the wrist pin bolt, the pin/piston assembly should be held by a solid rod through the hollow pin--no stress on the rod I beam section.
When tightening the cap on the crank, one is relying on the crank and Babbitt to hold the rod itself in place. I don't see any way around this process.
By following these procedures, I believe one has the best chance of an engine assembled with aligned rods (given that they were aligned before assembling).
If I missed something, let me know, as I have my own engines to assemble sometime in the future!
But be kind, OK?
Thanks!

Rick & I are pulling all 4 rods and pistons this morning and sending them out to be tested and straightened at a place we are very comfortable with. Once returned and installed, I will post the results. The man doing the work for us contacted me PM because he didn't want to get into the bickering. We also have not disclosed the rebuilder because we are not positive he did anything wrong in the rebuilding even though we have our opinion. Again, I want to thank everyone who posted positive suggestions and brought us to this final decision. I'll post under a new thread and call it an update of engine question. Have a great day. As for me and my house, We serve the Lord. Bob

Interesting how this forum often becomes a boxing match Bob! Here's what I live by: "If He leads you to it, He'll see you through it." You'll get your issue resolved.

This thread has been extremely interesting, informative, and possibly educational.

There are 2 distinct sides to the debate and no fence riders. Some say "It is definitely bent rods" while others say "It is definitely NOT bent rods".

We will know the answer to the question whenever Bob & Richard install the straightened rods and run the car.

Myself, I have been in their same situation, with their same symptoms three times over the years and I know how my fix turned out. My defective parts hang on the wall in my shop, as reminders.

We will see if their fix turns out like mine or if it differs once the car is up & running again.

Good luck guys!

David I agree with you on all of the above except how to "hold" the rods. You can not clamp the rod in any way, or means, and not bend the rod when tightening the wrist pin bolt. It is the twisting of the rod that happens while tightening the wrist pin bolt that usually does the bending. The only way I know to safely tighten the bolt is by sliding a rod thru the wrist pin bolt or using a special "piston clamp". I use a large phillips screwdriver that will slide thru the wrist pin. By clamping the protruding end of the screwdriver in a vice, the piston is "captured between the handle and the vice and there is no danger of it slipping off and damage it. The "special" piston vice is a vice with curved jaws shaped like a piston. The jaws are usually "lead lined" so as not to damage the piston. They clamp the piston at the top and strongest part of the piston. Im not claiming to be an expert by any means, but I have built about 30 engines thru the years. (they are all still going) and I have found no way to clamp the rod with out damage. Submitted with respect, Donnie Brown

For many years I worked for a company that, among other things, manufactured connecting rods. Even when making brand new rods, they each had to be inspected for bend & twist. Understand that when we use the terms "bend" & "twist", it does NOT imply that the rods have been damaged or distorted in any way. These are just the descriptive names given to the error in a connecting rod. So, when Frank asks, "...T con rods are always bent, twisted or out of whack in one way or another, ...how does this this happen?". The answer is, the rod does not necessarily get physically bent or twisted. It just displays error that mimics how a bent or twisted rod would appear. Again, "bend" and "twist" are just descriptive terms, used to illustrate the type of error experienced when making new rods, or rebabbitting old ones. Whether those errors are due to inaccuracies in a newly manufactured rod, OR NEWLY REBBITTED rod, are immaterial. The fact is, those inaccuracies DO exist and "bend" & "twist" are the industry verbiage used to describe it. For a third time, the terms not used to describe damage, just error.

The end result is that the rod, new or rebuilt, must actually be bent & twisted to bring it into alignment and make it useful.

Well said Jerry, and Donnie.

Thanks

Herm.

Donnie,
I agree, that is what I was trying to suggest for holding the piston pin while tightening the bolt. I think your explanation was better than mine. I was thinking of a steel SHAFT (I shouldn't have used the word "rod" because of the confusion--oops) held in a vise--a screwdriver would work too though!
I too, will eagerly await the results on this engine!

Here are a few pics of the tools Im describing. The piston vice is an old original "Stevens" tool. I do not use it as one of the "lead faces" for the jaws is missing. I could fix it fairly easily, but I use the other "tool" It is my trusty phillips head screwdriver. I have used it so long it is now considered a "model T tool" and stays with all my other T tools. As far as I know there are no other safe ways to safely tighten the wrist pin bolt. If there is I would love to learn a new trick. Again, Im no expert and still learning new things all the time. Respectively submitted. Donnie ..

Curious if there is excessive





horizontal clearance between the rod bearings and the shoulders of the crank throws.

Well I sure have learned a thing or two from reading this thread, and I'll put them to good use when I put my engine back together. Thanks!

Now I'm reasonably sure where that knocking in my engine was coming from!

Question for Bob Benedict: what kind of tires do you have on the '26 Coupe in your profile? They have a really nifty looking tread.

I use this for tighten the Wirst pin bolts.
Toon

Anthonie. Nice tool. Its a fancy and nicer version of my screwdriver. Thanks for showing it... I may need to make me a set.

I put a 5/16" punch through the piston pin and fasten it like Toon in the vice. (Haven't got any fitting screwdriver like Donnie, my thinner ones would have been bent)

Donnie,
I'm so dense, I was thinking of the screwdriver Handle end in the vise--your picture makes so much more sense; the handle keeps the piston in place too!
Anthonie's set up is neat too, but I don't think my vice opens that far! His does center the pin though. Hmmm

Eric, My coupe is at Ricky's shop right now. He has heat. We are installing disc brakes. I'll check the tires when I go there again soon. They came with the car and are fairly old but in excellent shape. The rods with pistons are gone to the straightener and should be back first of the week. In removing the 4 rods we found the #4 rod to piston bolt, even though it was wired, was only finger tight. This is the reason for the wiring. It works when someone forgets to tighten the rod nut. We still believe our knock comes from the #3 being bent since the knock would go away when we shorted out the spark plug when running but #4 was a problem waiting to pop up. We have another motor being rebuilt and should be back within the near future. Our intentions are to immediately pull the inspection cover and check it over before install. This motor has made us a little paranoid when it comes to rebuilt motors. Bob

Bob,
Sounds like the best decision would be to tear down your engine completely and check everything over.. If the former "rebuilder" forgot to tighten #4 piston clamp bolt, then what else did he forget?

Roger,We have already checked the crank and tightened up the caps. We are running out of time for the driving season and have reservations for three tours this year. We are comfortable with the rest of the motor as it sits once we get the piston issues taken care of. The car has been driven this past year with no issues accept for the knock. The only reason we tore it down now was that the knock was getting worst lately. Your suggestion is right on but we are going to gamble with it staying together. With these cars especially, anything at anytime could put you out of the race. Bob

Anything can happen with them anytime, that's for sure - and it's a gamble we love when driving out of push distance from the garage

Fortunately help to get home (if needed) is only a phone signal away nowadays with cell phones.

With caller ID you really find out who your real friends are when broke down in the middle of the night or when on vacation. LOL

I "bumped" this thread up to bring it closer to the later thread entitled "Engine Question #2" as there is a lot of information in these two combined threads.

Followup thread.

http://www.mtfca.com/discus/messages/506218/524296.html?1425932424

Followup thread.

I don't know what it is about Model T rods, but newly babbitted rods always need to be checked for straightness.

Even rods that are freshly re-babbitted and have been placed in a specially made jig and bored in the vertical mill need to be checked for straightness. Logic might dictate that the rod should be straight, but there is a difference between theory and practice, and I always check my rods for straightness on a proper rod straightening jig.

I would question the competence of an engine rebuilder who put freshly re-babbitted rods into an engine without checking them for straightness.

But then, that's why I rebuild my own engines, trusting the machine shop only to bore the cylinders, and maybe replace the seats, after I have reamed the valve guides with a proper automotive valve guide reamer and a special jig to ensure the reamer is going through the guide straight.

Respectfully submitted,

Trent Boggess

"In theory, theory and practice are the same; in practice, they're not."

Yogi Berra

Trent,

"...but there is a difference between theory and practice..."

Truer words have never been spoken, (in theory).