03-29-2020, 03:12 PM | #1 |
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Loose Rod
I am re assembling an engine that has been rebuilt and I have a problem. After applying 50 pounds of torque, the rod is still loose on the crankshaft. This is with new rods and insert bearings. No shims. Was the crankshaft ground too far?
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03-29-2020, 03:52 PM | #2 |
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Re: Loose Rod
If you don't have measuring tools Use aluminum foil--- figure how many layers lock it up--try the rod and bearing on a different journal see if it fits different -
Guess I should have asked which way it is "loose", it should move side to side a little--- but if it rattles around in every direction--- and check the bearing inserts for the size or other numbers and look at the others to see if the same |
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03-29-2020, 03:52 PM | #3 |
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Re: Loose Rod
Whats the clearance ? Thats a must know.
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03-29-2020, 04:15 PM | #4 |
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Re: Loose Rod
I was having too much rotational play on the crankshaft. I took the rod off of #1 and switched it with #4, and now it fits better on that one. But I tried the rest of them out and they have the opposite problem of being too tight. Guess I have to get shims now for the other three?
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03-29-2020, 04:21 PM | #5 |
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Re: Loose Rod
Why are you into this block? What is the rebuilders opinion? Is not 50# on the rod nuts a bit much?
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03-29-2020, 04:38 PM | #6 |
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Re: Loose Rod
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03-29-2020, 05:22 PM | #7 |
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Re: Loose Rod
I should not have said rebuilt. I had the block machined and parts purchased. Reccommended torque on the rods is 45 pounds.
How else can I loosen a rod up?
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03-29-2020, 05:53 PM | #8 |
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Re: Loose Rod
You have a problem there. Insert bearings are available in standard and plus sizes to fit known crankshaft crank pin journal diameters. The crank pin journals need to be measured with a micrometer to see if they are close to some standard or oversize diameter. The bearings inserts should be of a known inside diameter and fit snug to the con rod big end with the locking tabs in their respective grooves. Plastigauge can be used to check clearances. Bearing shells should be marked for part number and size on the back of each shell. Check all this yourself or contact the shop that did the work for help.
The crankshaft may need some time in a crank grinding machine if the sizes don't match up. Only a poured babbitt block & connecting rods need shims. |
03-29-2020, 06:59 PM | #9 |
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Re: Loose Rod
When they machined the block did they have the parts to gauge?
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03-29-2020, 08:51 PM | #10 |
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Re: Loose Rod
Yes they had all of the parts. They are a pretty reputable shop around here, they know Model A's. Which is why it is odd to me. So my inserts for the rods might be too large?
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03-30-2020, 12:12 AM | #11 |
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Re: Loose Rod
Hydrodynamic principal is .001 clearance for each inch of shaft diameter..on a model a engine the correct oil clearance is .0015,regardless of the bearing used,insert or poured.Fit your connecting rods to this standard.Shortcuts are not the formula for bearing life.
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03-30-2020, 12:48 AM | #12 | |
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Re: Loose Rod
Quote:
This is a common and puzzling error made in parts catalogues and repair manuals that I have seen.
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03-30-2020, 06:30 AM | #13 |
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Re: Loose Rod
I have assembled upwards of 180 engines with inserted rods supplied by Antique Engine Rebuilding (AER) and of those, I have run about 100 of them on an engine dyno to break them in. What I have learned from this work is that rod clearances need to be between .0015" and .0018" based on the methods I use to check assembly clearances. Much over .0018" and a slight rod knock may start after 2 hours of running/break-in. With over .002" clearance it is most likely to develop a knock during the break-in. I have not tried less than .0015" during assembly and at that clearance, I have not had a bearing failure due to lack of oil clearance at a rod bearing.
The suggested final rod bolt torque is 35# for AER and Snyder's insert bearing rods. If torquing to 45# there is a risk of twisting/distorting the rod cap. This twisted condition may also cause a rod knock. When checking rod journal diameter during assembly, I find that a mid-range journal size within the rod and bearing manufacturer's stated spec. provides the clearances I am looking for. For loosening the fit on the tight rods, I suggest taking the crankshaft to a crankshaft grinder and have them polish the journals until you obtain the proper fit. Most shops will have a motor driven abrasive belt polisher to complete this adjustment. I have had this process done a couple times prior to purchasing equipment for my Sunnen precision pin hone to adjust the fit. I hope it all works out well for you. Good Day! Last edited by Dave in MN; 03-31-2020 at 07:42 AM. |
03-30-2020, 07:56 AM | #14 |
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Re: Loose Rod
Hydrodynamic lubrication is used on all types of machinery,its the basis for lubricating internal combustion engine shafts,pressurized or gravity system,insert or poured bearings,high or low compression just about every engine runs on a thin film of oil. Whats interesting to me is its a standard measurement,.001 clearance per inch of shaft diameter..run a 10 inch crankshaft journal? its hydrodynamically supported by .010 film of oil.This is where folks get confused with journals and bearing sizes and all kinds of hoohah about engine oil...get .0015 with a model a rod and it will live a long life,use an engine oil with high load and shear characteristics to protect the film.Diesel grade engine oils have these additives. If the bore is cut correctly and the crankshaft and bearings are fit to .0015 on your rods you are golden.If you can shim your insert bearings to achieve .0015 youre golden...yep,the golden rule doesnt change..fire your machinist? maybe but you can make a tight insert work with fitted shims |
03-30-2020, 09:43 AM | #15 | |
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Re: Loose Rod
Quote:
One problem I have had with inserts are interference with the radius ground on the crank journal. It is pretty easy to identify when you are looking for it. If this is the case, a bearing scraper can be used to relieve the edge where it is riding on the radius. It also sounds like the crank may have been ground with different size journals. While this may sound like a hack job, it may have just been repair work over its life. Do you have a tool, (caliper or micrometer) to measure the journals? J
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03-30-2020, 01:23 PM | #16 |
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Re: Loose Rod
Have you talked to the shop that did the work??
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03-30-2020, 04:16 PM | #17 |
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Re: Loose Rod
I do need to bring out the micrometers and do some measuring. Discovered the bearings are .030, and this is on new AER rods.
I have not talked to the shop yet. I want to try and solve this on my own, but it is looking like maybe not. I have some shims coming on the way as an option.
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03-30-2020, 04:48 PM | #18 |
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Re: Loose Rod
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03-30-2020, 05:11 PM | #19 |
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Re: Loose Rod
I bought laminated shims from Brattons.
https://www.brattons.com/brass-conne...rod-shims.html
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03-30-2020, 05:57 PM | #20 |
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Re: Loose Rod
Chris,
one of the factors to making inserted bearing work properly is the deterministic nature of the design. The rod, or block bore is to a specific size and round within tolerance. This is done to make the insert pair conform and crush for proper retention, and resistance to spinning. By adding shims, you are in effect distorting the bore and more than likely will cause problems. I am quite certain that the AER rods are precision machined and sized for the bearing inserts. It is probably best to contact AER and get the bearing size information and then determine the course of action. As I mentioned earlier, checking the radius clearance is paramount and not hard to do. John
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03-30-2020, 06:01 PM | #21 |
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Re: Loose Rod
I would never shim an insert bearing. Either the crank will need polishing or something is wrong with the bearings.
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03-30-2020, 06:37 PM | #22 |
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Re: Loose Rod
It sounds like I should polish the crank and maybe make a phone call.
Should have thought twice about the shims. I just want to figure it out and get it done.
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03-30-2020, 07:06 PM | #23 | |
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Re: Loose Rod
Quote:
Well I learned something new today. In the 50 plus years I've been fooling around with old cars I've never heard about bearing shims like these. Has anyone actually tried them, do they work or are they like sawdust in the crankcase? |
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03-30-2020, 07:21 PM | #24 |
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Re: Loose Rod
They have been used a lot to keep an engine going a bit longer after they got worn out.
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03-30-2020, 07:22 PM | #25 |
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Re: Loose Rod
If everything else checks but the full bearing clearance to the journal then a shim can be an effective repair,as long as it covers the tang of the bearing it shouldn't give you an issue.But,that isn't the proper fix,who ever cut the block fitted the bearings and crankshaft has some explaining to do if your findings are accurate.
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03-31-2020, 09:12 AM | #26 | |
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Re: Loose Rod
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Quote:
There's some fitting needed depending on how much shim you use, some has to be filed off the parting surface of the insert so it doesn't buckle--- file too much and it's too loose and will spit out shim and spin |
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03-31-2020, 11:17 AM | #27 |
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Re: Loose Rod
Years ago we used what we called "check paper" under insert bearings. We went to the bank and got blank cheques and cut them up for shims. Worked good on old tired engines.
Anyone else remember the crankshaft grinding while the engine is still in the car?
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04-01-2020, 09:49 AM | #28 |
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Re: Loose Rod
Yes I did it when I first started working for my Dad in his repair garage. I still have the grinder. I have used it to grind rod journals on a model A crank in my lathe.
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04-01-2020, 05:09 PM | #29 |
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Re: Loose Rod
When I was in my teens, I watched my father shim the insert bearings in his very tired Austin. He switched top shells to the bottom and vice versa and used cigarette papers behind the worn ones (the ones with little loading) When more than a single layer was required, he cut the extras at decreasing lengths to get the tapering effect. He cut holes in the papers for oil after that.
We drove he wheels off that car for years but I think I'd use metal shim material which is available from 0.001" thick.
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04-01-2020, 07:55 PM | #30 |
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Re: Loose Rod
I talked to the shop after I determined that it was the inserts and not the crank journals. Ever ugh once in a while, an insert or two might be off a bit so it happens. He will probably hone a few thousandths off, if that.
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04-01-2020, 08:15 PM | #31 |
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Re: Loose Rod
Loose rods need building up not honing. What did I miss here?
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04-01-2020, 08:24 PM | #32 |
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Re: Loose Rod
The loose rod problem was fixed by switching the rods to different journals. The other two fit too tight.
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04-02-2020, 06:13 AM | #33 | |
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Re: Loose Rod
Quote:
Seems more likely the journal sizes are off spec. Just speculating. I hope it all works out. Good Day! |
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04-02-2020, 07:55 AM | #34 |
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Re: Loose Rod
Jack Shaft is right on. It seems like someone doesn't know how to use measuring gauges or measure. The crank journals should all be the same dimension within +/-.0003". The rod inserts should all be machined the same and mated to the crank approx. +.0015" according to Jack Shaft. It would seem to me that if the above has been applied you should be able to install a rod in any position blindfolded and have the same results.
Torquing is not the solution. If the crank journals are not all the same have your machinist make them all the same. Then buy new rods that are properly mated to the new crank journal dimension or re-machine the inserted rods you have to properly fit the crank. This would probably involve removing material from the caps and reboring the inserts to the new crank diameter + some clearance (use Jack Shafts spec). |
04-02-2020, 08:32 AM | #35 | |
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Re: Loose Rod
Quote:
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04-02-2020, 08:51 AM | #36 |
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Re: Loose Rod
It is not the crankshaft as those two rods are stilll tight on every part of the crankshaft. They might just give me different inserts.
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04-02-2020, 09:07 AM | #37 |
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Re: Loose Rod
I wonder if these are custom made bearing shells or if they are using some Kubota tractor bearings or what have you. The bearing material is layered with the final layer generally plated onto the surface. To remove any of the layers would not be something I would not even consider. The manufacturer of the bearings needs to get their ducks in a row on their processes. Out of spec journal bearings are bad products and the manufacturer should lick that calf over until there is satisfaction for the end user.
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04-02-2020, 09:14 AM | #38 | |
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Re: Loose Rod
Quote:
Have not heard that one before, had to think about for a few seconds to understand it, but I do like the phrase. |
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04-02-2020, 09:59 AM | #39 |
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Re: Loose Rod
That is the issue with inserts,wear through the thin layer of babbit and then you begin wearing the part it bears.Neither copper or steel backed inserts have forgiveness when the babbit is gone.
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04-02-2020, 11:58 AM | #40 |
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Re: Loose Rod
Problem solved. It was human error on my part: I accidentally switched the rod caps between the two. Now they fit perfectly. Mistakes happen.
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04-02-2020, 12:03 PM | #41 | |
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Re: Loose Rod
Quote:
Guys: Look at his post above. He states he is using AER (Antique Engine Rebuilding) rods. If these rods and inserts were purchased within the last 8 years, the inserts are not tri-metal. They consist of a steel shell with bearing grade aluminum applied. The aluminum is quite thick when compared to the last layer of a typical tri-metal bearing. The rod bolt spec for torque on an AER rod is 35#. I recall from his earlier post that he was torquing to 45#. (50# in one case.) If he is torquing to 45#, he could be twisting the cap and binding the bearing... "More" is not "better" when torquing to a manufacturer's spec. I have used lots of the rods and inserts from AER and they have all been consistent in sizing. ("Lots" equals over 180 sets...that's over 720 rods and insert shells) Given he changed a loose rod to a different journal and it corrected the problem...either his method of assembly has changed or the diameter of the rod journals vary. Or am I missing something here? I still suspect the rod journal diameter is not consistent. Follow-up: I just saw his follow-up posted while I was typing this. He had the rod caps interchanged. Problem solved. Good! But...I still suspect the rod journal diameter is not consistent. Good Day! Last edited by Dave in MN; 04-02-2020 at 12:41 PM. |
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04-02-2020, 02:42 PM | #42 |
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Re: Loose Rod
See, it is good that we kept nagging at you. Now you can have a good time touring the countryside. I'll bet you never do that again.
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04-02-2020, 03:40 PM | #43 |
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Re: Loose Rod
Bravo!
Honest mistake, but something to ponder, as technology changes so does the discipline. Put it together and enjoy, J
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04-02-2020, 04:25 PM | #44 |
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Re: Loose Rod
This just didn't add up, something was wrong. Its nice the problem was found, but, the rods and caps should have been marked.
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04-03-2020, 12:40 PM | #45 | |
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Re: Loose Rod
Quote:
They are. Each rod has a unique number within a set of 4. The rod and cap are each stamped with the same number on one side. Keeping the numbers directly aligning on the cap and rod is how you know which way to install the cap on the rod. (and, in this case, which cap goes with which rod.) Good Day! Last edited by Dave in MN; 04-03-2020 at 01:48 PM. |
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04-03-2020, 01:19 PM | #46 |
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Re: Loose Rod
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04-03-2020, 01:36 PM | #47 |
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Re: Loose Rod
Same here! Honest mistakes are OKAY as long as you recognize them.
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04-03-2020, 02:44 PM | #48 |
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Re: Loose Rod
Mistakes are just a part of learning. If any mechanic ever tells you they've never made one then he's pulling your leg. In your case you caught it before it got out of hand so that's a good thing and will make you feel a lot more confident. It makes a person careful to check things completely before changing tactics that might do more damage than good.
I've found that the guys who admit mistakes quickly and move on are much less likely to make mistakes in the future. It's a sign of good character and something a few of folks I've know over the years could use more of. |
04-03-2020, 03:11 PM | #49 |
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Re: Loose Rod
Just make sure your wife doesn't recognize them, that will last FOREVER.
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04-03-2020, 03:26 PM | #50 |
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Re: Loose Rod
Scars on the wallet stay forever!
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