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MG TD TF 1500 - BINDING CRANKSHAFT

I realize this is going to be a question for my machinist, but, I can ask one to anybody with engine assembly experience. I am assembling a newly machined 1250 engine for my TD. It was line bored and balanced. When I start to tighten the rear bearing cap the crank seizes up solid with almost no torque yet applied to nuts. I confirmed the bearing clearance with plastiguage. I swapped bearings around to no avail. I have noticed that the bearings extend just a bit past the legs on the main bearing caps. Is this normal? If they grind down the caps a bit before line boaring, maybe he forgot to file the bearing ends. I just don't know. Any comments on this? Thanks as always, Sandy.

smb brainsky

Take your own advice and take it back to your machinist. I would not touch a thing, it should fit without binding, especially without torquing up. JMHO. PJ
Paul161

The locating pin looks as though it may be proud of the bearing surface.These pins are removed for line boring.
The bearing are slightly proud of the cap until tightened down and must NEVER! be filed.
Also try assembling the crank without the centre cap as I have seen them tighten up as the centre cap was fitted wrong way round.The oil grooves should NOT line up with each other.
Ray TF 2884


















Ray Lee

Yea , I'm pretty stumped here. My pins are deep enough in. It's just the picture angle I took. I guess I just have to drag the block back to the shop again. This will be the 2nd time. Not very confident in my machinist any more. Had problems with getting the cam in after I originally got it back so I returned it to him. He gave it back with cam installed and rear bearing in wrong. Now this. It's all about the rear cap. Other 2 seem fine. Thanks though. I will let you know how this works out. Sandy
smb brainsky

Another thought... I had a similar issue when I was assembling my Sunbeam Alpine motor a couple of years ago. Turns out the bearing shells that are now available are NOT being made to exacting standards. Mine were way off in terms of sizing and as a result I had to get the crank cut to the size of the installed bearings. I was NOT a happy puppy. I suggest you install the bearings without the crank in place and then measure the inside diameter of the bearing surface... I'm betting it's too small (i.e. the bearing shells were made too thick).
Kevin McLemore

I would question the line boring if you are confident you have all the caps installed correctly. There should be a mark to denote direction or the orientation of each cap to the webbing. I.e. Center punched dots next Te each surface. Barring that you may have a bent crank i.e. It got dropped after it was machined. If the block wasn't absolutely cleaned and debri was under the cap when line bored and subsequently the offensive material removed afterwards it would cause the cap to not be perfectly machined and would clamp down on the crank when torqued. If you didn't wipe the bearings down you should see a shiny spot were the interference is on the bearing surfaces. My money money is on a bent crank or improper line bore
Bill Chasser Jr

Honestly, I don't know what to say about this. It is a puzzle. Plastigauge reads about .002 which is right in there. The other 2 bearing caps don't even have to be on the engine and it still locks up with just over finger pressure on the nuts for the rear cap. The pins are sitting way bellow the surface of the bearing. The crank was just re-balanced by a second machine shop because I bought a new clutch. Crank spins fine without rear cap on. I still think the bearing needs to have it's end filed a touch. I can't visualize anything else. But I won't touch them because I don't want to destroy them when I'm all wet with my idea here. Tomorrow I will make a call and see what he has to say about it. I promise to let you all know. I hope it doesn't get worse before it gets better. Sandy
smb brainsky

Sandy as a result of the line boring, the rear oil thrower or slinger needs to be hand fit.
Remove the crank, coat the slinger surface with dykem or a magic marker, install crank & rotate, remove crank, dress slinger just until6 it does not touch the crank.
Call me 914 420 8699
Laf48@aol.com
Len Fanelli

Sandy refer to my post on the Moss oil seal bbs a few posts down
Len Fanelli

Sandy

Very comprehensive article here that might assist:

http://www.mgccyregister.co.uk/technical-information/the-xpag-files/xpag-rebuilds/xpag-engine-rebuild/xpag-engine-rebuild-questions-and-answers/

Graeme
G Evans



Sandy--- The problem is what Len said! Give me a call at phone 270-384-0344, and I will tell you the info you need to know about your line bore and why your crank is locking up. Too much info to reply to on line in the forum. If you want to update everyone after the fix that would be cool. I've been through the same issue, so I know it can be solved.
Richard Cameron

Ugh I forgot about the stock slinger. I didn't know it could cause the issue. I'm still learning. Hope you get it resolved to your satisfaction. I will be interested in knowing the out come.
Bill Chasser Jr

One further item that haven't see addressed, the thrust barrings could be too thick. I had to lap the back side of the thrust bearings in the engine for our TD to prevent them from binding when everything was reassembled. Cheers - Dave
DW DuBois

Most of the new bearings have sharp/square front/rear edges, and turned or new cranks have very rounded "fillets". Make sure a sharp corner is not binding. Yes, they are supposed to stick up slightly. When torqued, that is called bearing crush. I would also try front and rear without the middle bearing, that would rule out Dave's possible problem. George
George Butz

Didn't say anything, but that was my thought also Dave, as it was a problem when I rebuilt one of my old tractor engines which is very difficult to get the proper parts for, especially main and rod bearings. PJ
Paul161

I am now pretty positive the binding is from the line boring. No attention was paid to the oil seal and now it is contacting the scroll. The caps were indeed cut down about ten thousandths and the original clearance around the scroll was much less than that. He is a good machinist, just not versed in our engines. I am now vetting other shops that the great people in our CT club have been referring to me. I will let everyone know how this all works out. I am quite surprised at the interest this has garnered. A big thanks to everyone. You all indeed help me to keep up a head of steam. I can see how a person can get discouraged and back burner a project. Happy New Year, Sandy
smb brainsky

Sandy if the line bore has to be done again. Note the piston height a TDC on install and check valve to piston interference if your head is heavily shaved or you have pop up Pistons to increase compression. Also check for proper timing chain tensioning I don't know if will make a difference or not but it is problematic on chevies when multiple line bores are performed

TD 4834
Bill Chasser
Bill Chasser Jr

The book "MGTD restoration manual " by Horst Schach has a good description of the fitting of the scroll-type oil seal. If the block has to be line bored, a careful fitting of the aluminum rear seal with the crankshaft seal has to be done. Interference of the scroll with the aluminum rear "seal" is a result of the line boreing, not a botched job by the m/shop.
I doubt that a regular automotive engine rebuilder would be familiar with this tedious, trial and error process.
T W Moore

"No attention was paid to the oil seal and now it is contacting the scroll" Sounds like that is the problem. The fit of the scroll seal has nothing to do with line boring. Completely remove the metal seal, and see if the crank is free. If you just randomly fit the "seal" without following proper procedure, most likely it is just jamming against the crank scroll. Several good write ups on how to fit out there, I think the NEMGTR handbook has one. It involves oversizing the dowel holes or removing the dowels, using machinist's bluing and a lot of trial and error. George
George Butz

This discussion seems to be getting off track. One thing that some might be forgetting is that the cast iron rear bearing cap serves as one half of the seal area adjacent to the crankshaft Archimedes scroll.
I don't think the aluminum seal plate has anything to do with Sandy's problem in this case. It probably isn't even installed yet.

Probably What happened is that his machine shop line bored the main bearing saddle housings but didn't do the seal bore at the rear of the cap. So when they removed .010" from the main cap mating surface to facilitate the line bore, that moved the cap .010" closer to the crank and the original sealing area wasn't touched so it now hits the scroll on the crankshaft and locks things up.
Richard Cameron

Sounds like Richard is correct, if so the part of the bearing cap that contacts the scroll can be dressed with a whetstone, or emery paper.
The upper slinger or thrower can be dressed with a single edge razor blade.
Len Fanelli


Len, not wanting to disagree because I'm sure you've hand dressed a cast iron cap yourself before, but in this case, I doubt Sandy has the ability to do this at home.
For one thing, we really don't know how much will have to be removed because we aren't sure what the original clearance was or how much the machinist actually removed from the cap mating faces. Judging from my own experience, it wouldn't surprise me to find that a minimum of 0.005" would have to come off the cap seal surface to free the crank. IF so, That's a lot of sanding and trial fitting on cast iron.
Even though not desirable from a cost/time stand point, my thought would be to fit the aluminum seal plate against the crank scroll, file its edges so the cap doesn't push it away , and take the whole thing back to the machine shop for line boring of the seal area concentric with the main bores.
Richard Cameron

Above is true, I assumed by "oil seal" he meant just the aluminum part. Yes, the main bearing cap part could contact too.
George Butz

To resolve this problem despite all the good advice there needs to be a clearer picture painted of what is assembled on the motor when the crank shaft binds up.

Is the Oil Thrower, rear upper main installed,are the center bearing cap and bearings installed when binding occurs?

If there is binding when these items are removed the logic expressed regarding the rear bearing cap seal area not being machined comes into play.

To prove if this is the fault, blue up or coat with a felt pen the "Archimedes Screw" area of the crank, just place the rear cap in position and apply downward pressure, rotate the crank, any witness marks transposed to the seal area will prove that it requires modification.

I want to repeat use the documented advice I previously posted, that has been learn t from experience, to carry out further diagnosis.
G Evans

I usually get the machinist/mechanic to assemble my engines, at least the bottom end - it's up to him to make sure any issues are resolved. Unless you are experienced or trained in assembly, I think this is the best way to go.

The idea of an owner getting stuck into bearing caps and the like, using well-meaning advice based on partial data, scares the hell out of me. Get someone who'll give you a warranty and hold him to account if anything goes wrong.

Regards, David

David Provan

I've watched this thread with interest and it surprises me that no one has suggested the use of a metal scraper. Yes! I know that is going to be an anathema to some of the current technology and some of the folks here who suggest "give it back to a machinist"; HOWEVER, the current parts are NOT made to the tight specs of the not too distant past. Many of the current bearings are not going to allow you to simply put them in and bolt everything together and not have the crank and pistons and cam spin perfectly..... Pipe dream! You are going to have to fettle no matter what.
When I started my mechanical apprenticeship with the Rootes Group in England, at The commercial division Commer Carrier in the early sixties they showed us how to scrape bearings..... An absolute necessity! If you wanted an engine to turn over properly.... You used blueing and scraped the high spots til things worked. Now current experience... I've done two XPAG engines in the last couple /three years for my project and I've had to scrape EVERY bearing in both motors (heir and a spare). The first engine fired up the last fall and seems to be working perfectly. So! My advice to anyone with tight bearings, mine new from Moss were 10 thou over on one engine and 20 thou over on the second, is get a scraper off of eBay and start fettling. If you haven't done it before check YouTube! Old ways STILL work!
Best regards
Rod Murray 54 TF
Rodney G Murray

As far as I know, the only scraping of bearings should be to the centre thrust faces on XPAG engines as these are made oversize to factor in wear.
I was taught that shell bearings are not to be scraped.
If sent an incorrect bearing then return and complain.
There is not enough bearing metal to accommodate scraping the journal surface. Fair enough, scrape and fit cast bearings but not shells.
If proven wrong then I will apologise.
Ray TF 2884
Ray Lee

I have bearing scrapers, but their only to be used on Babbitt bearings. As far as I know, Babbitt hasn't been used in years, but could be wrong. PJ

Paul161

I did say that some would not find this to their liking but let's look at what mostly happens when you have to install say new mains! First the manufacturer of this cast bearings is supposed to provide correctly dimensioned (to tenths of a thou) parts to fit what is usually a re ground ournal on a crankshaft, also ground to tenths of a thou. Now it is required that the mating surfaces be free of any blemish and that the dimensions of all mating parts come together in a "tolerance " fit. With absolutely NO high spots that will bind. I put it to all that the probability of this being achieved is very small and that being able to send back multiple bearings to a supplier while you try to get one to fit will soon pale on that supplier. Especially if you have ground/filed/sanded the front face of the bearing to fit on your particular journal. Based on that fact alone the bearings should NOT go back. Typically you have NO choice but to adjust/fettle the front face to get the bearing to sit down on the journal as it has been pointed out that the front face is deliberately cast slightly bold so that they can be made to fit every journal.
Secondly, when you start this process you have a choice to either do it yourself or have someone else do it for you. Now if you have someone else, say a machinist, do this for you he is not going to use arcane magic to remove material if when he locks down the end caps and finds that things are binding. He is going to have to remove material as he is not going to be able to compress the bearing into submission. In removing the bearing material ( he normally won't touch the journal unless there is something wrong) he will have to use something do this. Some recommend sanding with Emory, some want to use a file. No matter what he is going to have to use something as he is not going to sit there swapping out parts til he gets a good fit. He needs to fettle fit the surfaces until he can achieve that tolerance fit. I was taught to use a scraper on the high spots of the bearing material then assemble spin and repeat until you have remove the offending material and all spins freely. The Rockwell hardness of the journal nicely highlights the high spots on the bearing when you spin.
If we are to maintain the breed fitting fettling is an absolute, thus we need to use every method old and new to ensur the parts go together with that tolerance fit.
I'm not trying to offend anyone here with disagreements only identifying techniques that I have learned and used and that I hope could help others in their DIY efforts.
Best regards
Rod
Rodney G Murray

I did say that some would not find this to their liking but let's look at what mostly happens when you have to install say new mains! First the manufacturer of this cast bearings is supposed to provide correctly dimensioned (to tenths of a thou) parts to fit what is usually a regrouped journal on a crankshaft, also ground to tenths of a thou. Now it is required that the mating surfaces be free of any blemish and that the dimensions of all mating parts come together in a "tolerance " fit. With absolutely NO high spots that will bind. I put it to all that the probability of this being achieved is very small and that being able to send back multiple bearings to a supplier while you try to get one to fit will soon pale on that supplier. Especially if you have ground/filed/sanded the front face of the bearing to fit on your particular journal. Based on that fact alone the bearings should NOT go back. Typically you have NO choice but to adjust/fettle the front face to get the bearing to sit down on the journal as it has been pointed out that the front face is deliberately cast slightly bold so that they can be made to fit every journal.
Secondly, when you start this process you have a choice to either do it yourself or have someone else do it for you. Now if you have someone else, say a machinist, do this for you he is not going to use arcane magic to remove material if when he locks down the end caps and finds that things are binding. He is going to have to remove material as he is not going to be able to compress the bearing into submission. In removing the bearing material ( he normally won't touch the journal unless there is something wrong) he will have to use something do this. Some recommend sanding with Emory, some want to use a file. No matter what he is going to have to use something as he is not going to sit there swapping out parts til he gets a good fit. He needs to fettle fit the surfaces until he can achieve that tolerance fit. I was taught to use a scraper on the high spots of the bearing material then assemble spin and repeat until you have remove the offending material and all spins freely. The Rockwell hardness of the journal nicely highlights the high spots on the bearing when you spin.
If we are to maintain the breed fitting fettling is an absolute, thus we need to use every method old and new to ensur the parts go together with that tolerance fit.
I'm not trying to offend anyone here with disagreements only identifying techniques that I have learned and used and that I hope could help others in their DIY efforts.
Best regards
Rod
Rodney G Murray

Well, as I noted earlier (and Rodney seems to agree), the bearings we're getting today are definitely not made to the proper tolerances - they can be off by a frustratingly considerable amount.

Modern tri-metal bearing shells don't really have much depth for actual bearing material, and that top-most surface layer is a *very* thin (.0005-.0008") layer of Babbitt which serves as a dry-film lubricant when the bearings have no oil film (for example, starting up after a long time sitting).

As a result there's not a lot of room to fettle, though I do agree that very slight high spots can be carefully scraped down, and Rodney's procedure for this is appropriate.

That being said, modern bearing shells can be *so* far off that in many cases to make them fit properly you'd be fettling off nearly all of the Babbitt and would likely even get down past the Babbitt and into the copper-lead layer(!), and that would be a serious no-no.

So, as I explained, the solution I use is to fit the bearing shells into the block *before* you dress the crank, torque down the caps to spec., and then carefully measure their inside diameter. Record that data for each bearing opening, subtract the proper bearing oil clearance amount from each, and then use this calculated figure to dress each journal of the crank to exactly fit each respective bearing shell set. I use an oil clearance of .0015-.0020" for 10W-30 oil and .0020-.0030" for 20W-50 oil for most LBC motors.

I should note that the old 'measure twice, cut once' rule is emphatically important here. I measure twice and then have someone else measure twice, just to be damn sure.

By doing it this way you end up being able to use the bearings as they were designed, with all of their Babbitt intact and sufficient oil film clearances to prevent overheating of the bearings (too tight) or 'slop' in the bearings (too loose).
Kevin McLemore

Ray,

There will be need to apologise for what you said about shell bearings is absolutely correct.

I have scraped many bearings over my lifetime but they were not shell or slipper bearings. They were bearings with a steel or cast iron base with white metal cast over the top. From then on one fitted those bearings to the journals using a bearing scraper taking off very small amounts of metal indicated by high spots reflected by the use of prussian blue.

My three penny's worth is don't attempt to scrape shell bearings if they don't fit then usually they are an incorrect size.

John...Sydney
John Walton

I hate to drag this on,BUT.
If there was a problem with shell bearings I am sure it would have come up on this board. I have rebuilt many XPAG engines plus other car and motor cycle engines and never come across a set of bad bearings.
I have however had cranks not ground to spec and have had to return them to be corrected.
The only type of bearing that requires scraping and fitting is a thick shell not a thin shell.
Ray TF 2884 (retired Marine and Hospital Engineer)
Ray Lee

I'm glad that others have had such good luck as to not have to adjust /fettle bearings in their past, BUT my experience has been the opposite and when faced with a dilemma of what to do NO ONE should remove a solution from their repertoire simply because they haven't had to use that solution themselves.
My last two engines (XPAG's)have seen me carefully remove high spots with a scraper to achieve free rotation of the crank in the new bearings. It would not have been possible for me to return the bearings to Moss because widths had to be adjusted BEFORE the bearings would seat properly. I also did not want to go messing with journals that looked and measured perfectly.
I too have spent a lifetime in either Mechanical or Civil Engineering roles and hope that even though I am retired I never quit learning new ways to overcome obstacles and find ways to share those solutions.
Best regards
Rod Murray TF 3006
Rodney G Murray

Ray,
I too am an ex marine engineer and sailed with Port Line a subsiduary of Cunard. Although being a fifth generation Aussie I sailed with an English company. Their head office and my home port was in Liverpool in the Liver building. Who did you sail with?
John...Sydney
John Walton

Another issue not mentioned here is the "housing diameter" after line bored (or rod resized). I don't recall if there is a shop manual spec for this, but it has to be exact. If too large, the bearing crush won't be enough and the bearing ID with torqued cap will be too large, and vice-versa. Years ago you could place a set of Vandervell (sp?) or other NOS bearings in place with a ground to spec crank and all was perfect. Not the case now between line boring, resizing rods, etc. due to lack of specs or variation/error in machining tolerances. In the late 80's the mains supplied began coming with really too wide thrust faces that required hand fitting, so the bearings have not been exact for years. Bottom line: the machinist has to be really good and understand the entire process. They seem to be few and far between now days. BTW, I'm in total agreement with Kevin's post above. George
George Butz

Hi John.
Brocklebank (Cunard Co also), PSNC, Moss Tankers (Cunard managed), Guinea Gulf.
This was just as National Service was finishing and they could not get engineers for love or money. I just swapped companies to see the world. It gave me a good grounding as a thousand miles from port means if you have not got it you have to make it.
Ray TF 2884
Ray Lee

Ray, Isn't it called improvisation?
John
John Walton

No posting from Sandy in almost a week - and progress?

Tom Lange
MGT Repair
t lange

Just a quick update. I just dropped my block with crank and pistons off at Accurate Auto in Middletown Ct. Machinist Blue on the scroll confirmed contact with the cast iron oil seal portion of the rear main cap. Martin there said that it involves a lot of careful measuring to machine this area, but he is familiar with our XPAG engines. I removed only 5 of the 6 new bearing pins I had just installed. The center one in the block will need to be drilled carefully to be removed. And apparently, my ever so critical sanding of my thrust surface measured a lot more on his bench than it did on mine so I may need to start over with a new set of main bearings too. He will check piston to deck height and an array of crank measurements. He suspects that the internal measurement of the thrust surface around the main journal of my crankshaft may vary at 180 degrees. (Bent?) I am considering lightening the flywheel while it is there too. It is becoming a money thing, so we will see. I don't know how this sounds to anybody else, but it's getting a little scary sounding to me. That Powerball would come in handy right about now. It could be a month before I get any news, but I will keep all interested posted. Sandy
smb brainsky

Glad to hear your progress. Sucks when you take a big step back and have to redo stuff, but at least you will have peace of mind.
I also lightened the flywheel while it was in the shop, seemed like a good time to do it..
Geoffrey M Baker

This thread was discussed between 27/12/2015 and 11/01/2016

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