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MG TD TF 1500 - main bearing bore

The machine shop asked me for the dimension of the main bearing bore in the block. In the data service of WKF Wood the bore is declared with 56,54 mm (2.2181 in)But this conversion is wrong. 2.2181 in are 56,34 mm!
Now my bore is 0,2 mm too large and I don't find bearings for this larger bore.
Does anyone have an idea to find a solution for this problem?
Kind regards
Klaus
Klaus Harthof

56.34 +- .01 is correct. Line boring IS recommended to bring the main bearing clearance down to .001" ( Inch) & the hand fit the slinger or oil thrower. When this is done oil leak from the rear main will be nil, or an occasional drip. (Oversize outside diameter main bearings are only used in opposed engines like Air cooled VW & Porsche as far as I know.
Len Fanelli
Abingdon Performance Ltd.
Len Fanelli


Len, Will Line Boring fix his problem or not. If it won't why do you tell him about fixing oil leaks on a standard engine? As far as I can tell from his post, his engine block has already been bored too much by 0.02mm.
Richard Cameron

Line boring again is his only solution. Let's hope they didn't take too much material out of the block the first time. Another line bore will raise the crank 0.008" to 0.010". Besides refitting the oil slinger, he will need to watch the installed height of the pistons as well. Depending on how many times the rods have been re-machined, you cannot have the pistons protruding out of the block.
A Peddicord

Thanks Terry.
Richard 1st the main bearing caps are milled at the parting line, then line boring brings the webs back to where they should have been. Quality control was poor at best on the main bearing web sizes IMO.
Len
Len Fanelli

Richard

the bore is 0,2mm (not 0,02mm) or 0,008inch too large, because that well known document is faulty.

As far as I know the block of Klaus has been shaved - so he has to pay attention. Also a modern oil sealing is present.

Whats about special bearings to match the oversized diameter? Are such bearings available? May be solution can be provided by a hungary factory - see www.maschinenspezialist.com. I met the owner at an exhibition.




W_Mueller

Klaus
What a disaster--
To be honest your machine shop should have known better or at least questioned why and double checked with you
Best fix is to have the caps machined down and tunnel bore it again. It's going to be a big cut now though to get down(up) in the block far enough to clean the sides up to a satisfactory shape--then there's the issue of deck height etc as already mentioned
A set of .010 os backed engine bearings would be nice and just open the block up that little bit but the chances of finding a set of them is hopeful to say the least
ACL here used to do them to order, what size is the crank itself---std-?
William Revit

No go
Just had a talk to a friend at ACL and they don't do os anymore, only for VW and some Porsche and Subaru- as Len mentioned
He reckons you'll have to bore it and will have to go around 2mm into the block to regain a full circle BUT suggested that getting a complete circle in the block isn't an issue, it doesn't need to be machined right up to the parting line, so maybe 1mm would do the job but suggested take 2mm off the cap, centre it up and bore it, just to make sure there is a full cut in the cap when it's done as all the load is on the cap and a full circle there is the go and don't worry too much if it doesn't quite completely clean up right up to the joint on the block itself--it would only be a mm away and some engines have a chamfer on them there anyway
Good luck
willy



2.2181 in === 56,34 mm
William Revit

I don't think a second line boring will work because of William's point. The sides will still be too loose. Brass or steel shims might work. If the bore is .008" too big, use .004" shims. It would have to be done carefully with all burrs removed from all edges and holes in the shims. The "crush" on the bearings should be checked in a dummy fitting. I was going to try that once in an HRG engine because I wanted to use "off the shelf" Peugeot bearings instead of using the original "poured" white metal. I didn't get to try it because I sold the car.

Perhaps a better idea would be to have the surfaces "metal sprayed" and then line bore again. That would be more expensive but maybe safer.


Good luck with the project
Bob Schapel
R L Schapel

Although the machine shop was given the wrong ID size, they had the block and should have checked the existing dimensions. As an engineer I would not accept somebody else's
measurements without checking, I think they should be sourcing a replacement block.
Ray TF 2884
Ray Lee

I was advised years ago (so systems may well have improved) that caution should be taken as "spraying" can de-laminate. I had my Lagonda crank submerged welded.I realize this is a negative and provides no solution. A horrible situation to have occurred. I sympathize but again that's no real help.
JK Mazgaj

I agree with JKs point. Metal spraying a crank or any sliding surface is a problem if it de-laminates, but in the case of a tunnel, where the bearing shells are not moving (and are in fact holding the sprayed metal in place) I think it should work well. If the block is the original and has to be resurrected, it might be the way to go (unless you want to try shims). However, if the block is not the original and a replacement block is easily available, that is another option. I once had some steel brake drums metal sprayed with cast iron (because cast iron has a better coefficient of friction than steel) and they held together well for the short time I used them. However, my friend, who ran the brake shop said the spray might as well have been gold dust when referring to what he should have charged me!

Bob
R L Schapel

Klaus,
Sorry to hear that news! There is a company in Hamburg called Carl Baguhn who will make custom size bearings and it might be worth talking to them before you proceed. The company seems to be a professional outfit. I have no experience with them but it is an alternative solution.
https://carlbaguhn.de/en/plainbearings.html

Regards
Declan
Declan Burns

Klaus,
Horst Wendling in Leverkusen has an XPAG engine dismantled in his shed. Maybe he would sell it. There is also a complete XPAG engine for sale on "eBay Kleinanzeigen" in Korschenbroich which is very close to me.
There is also a TD Hardtop on there!
Regards
Declan
Declan Burns

Wont be long I'm sure before this sort of problem (probably now if you can afford it) will be solved by 3D metal printing
JK Mazgaj

If I understand the problem then I agree with Bob S. Yes, taking metal off the sides of the bearing caps and then reboring will give you the correct top to bottom measurement but the sides will still be out, won't they, i.e., sort of an oblong hole?

Maybe I need a picture?

Gene
Gene Gillam

Some years back my crank broke and bell-mouthed the front main housing. The shop line-honed the block with either the wrong specs or just oversized it, causing lack of bearing crush and the bearing to crank clearance to be too big. The shop owner got a fellow that did a lot of work for Don Garlits out of retirement to correctly line bore it. This did raise the crank centerline- the crank nose is visibly higher and not centered in the sump/timing cover circle and we had to take a few thousands off of the pistons. Tom Lange recently explained that due to this the shop and I did not correctly fit the rear oil slinger and is why I have a really leaky rear main. So yes it can be done. If I did the math correctly, you only have .008" overbore which is very much less than mine was- I really think you will be fine with "snipping" the caps and boring again. George
George Butz III

Hi Gene, If you move further up in the half circle, it is narrower in diameter the further up you move. Trace around something round, draw a straight line in the middle. Then use a straight edge, move up and watch the diameter/length of the line shorten. George
George Butz III


George, There must be a mathematical formula or calculator out there somewhere that could be used to determine how much material would need to be removed from the parting surface to recover the .008" and get back to standard size. If so, one could determine if a re-bore would be possible. Seems to me that some material would need to be milled off of both the block and the caps to close up the part line diameter.
Richard Cameron

Maybe I wasn't clear enough in my earlier post--
The point at which the .2mm os bore is reduced enough to be rebored back to the std. size is 2mm from the parting line-
By taking 2mm off the cap face a full half circle can be machined in the cap to the correct size
If the centreline of the tunnel is moved 1mm into the block from the parting line(which is the new centre between the 2mm reduced cap and the block tunnels) then a cut to the correct 56.34mm size will result in a full cut to the cap and a cut that finishes approx 1mm short of the parting line in the block
The cuts will be equal at .9mm vertical depth each in the cap and the block and 0 horizontally
The 1mm short of the parting line cut in the block is not an issue-some engines even have a chamfer on the edge that deep in that position
-------------------
To get a full cut in the block the centreline would have to be moved into the block by 2mm which is completely unnecesary and could cause more drastic issues with piston deck heights and timing chain (timing and tension) issues----1mm centre adjustment will do the job but there will need to be caution during assembly, checking the timing, chain tension piston height etc

Honestly---Your machine shop should cough up for another block for their stuffup but it's not the end of the world, it can be remachined as above successfully

willy
William Revit

This idea is a bit of a long shot. Is there a bearing with your "new" tunnel size (or bigger) in another model of car? You would have to get hold of a bearing list book from a company which makes bearings and search through it. The centre bearing with thrust flanges is likely to be the biggest problem in the search. In Australia we have a company named "Repco" and it had such a book. (It is probably on CD or digital now.)


Some "trivia". About 40 years ago I searched such a book and found various other big end bearings which would fit a T-Type. For example a Peugeot 403 big end bearing can be made to fit an XPAG because it has the same tunnel size. The "tang" is on the wrong side so the con-rod has to have a tiny grind in one corner. The oil hole is even in the right spot. The bearing is broader (full rod width) so might be better than original as long as the edge does not "bottom" on the crankpin radius. (They could be trimmed if necessary.) I have never actually used them. I think an Alfa bearing was also similar. I think I got the book to solve another problem and was curious.

Cheers,
Bob
R L Schapel

William,
2 mm is not correct. I have just measured it on my CAD system. It is 2.38mm.
Regards
Declan

Declan Burns

I spoke to Klaus last night and he has found a shop who can plate the outside of the bearings to match the bore.
He is on his way this morning to check out the feasibility. Could work?
Regards
Declan
Declan Burns

I guess that depends on the technique - melting, glueing - with or without heat.
W_Mueller

Winfried,
Plating- not melting or gluing.
Regards
Declan
Declan Burns

aah - something like that?

https://dycomet.co.uk/
W_Mueller

Winfried,
No that is metal spraying but also interesting. Klaus mentioned plating to me on the phone. It could be hard chrome-he did not specify but I am sure he will let me know.
Regards
Declan
Declan Burns

Declan
Ah yes hard chrome plating could possibly be a fix---
On the machining option--
I had only measured it out with my verniers, it was just over 2mm as you say but
-In the interest of taking the smallest possible cut 2mm would be fine- If the new machining in the cap finished 0.38mm short of the parting line, I don't see that as an issue- There's 177mm around each bearing shell so it would still have 176.24 coverage, more than enough I would suggest

Something else-in inches now
The ACL race series bearings manufactured here have extra crush built into their finished size---Where a normal bearing this size would have .003"-.005" crush, the race series have a .004"-.007" spec.
The reason I mention this is that if Klaus' plating turns out a touch thicker than he expects, there is a "little" room there for a tiny bit extra-
They'll have to be on the ball to get it spot on .004" coverage but taking these race series bearings spec. into consideration they 'could' go up to a max of .0045"and still be ok

willy
William Revit

Actually the centreline of the new bore would be 1mm into the block so would more than cover a full cut in the cap--------
William Revit

Unless you use another block, I still think the first option to investigate is metal spraying (or plating?) the tunnel and then line boring. Then the problem is fixed permanently. If you modify the bearings, the next time you damage a bearing or grind the crank, you have the same problem again. Raising the crank will also change the clutch/gearbox alignment (although I don't know how much starts to become an issue).

I would actually consider the shim idea (done VERY carefully). Crush should hold them in place. I don't think that ranks too badly amongst the other unconventional things I have done to engine internals. I would not suggest shims for worn bearings due to ovality and crush issues.

Bob
R L Schapel

P.S. I checked through my Repco bearing book but it did not reveal any bearings which would suit your slightly bigger tunnel size. (Although the book is about 40 years old!)
Bob
R L Schapel

Bob
I'm starting to think that the tastefull fitting of shims, although it puts a shudder through me, could be an option

I've had a measure up session and 1.6mm off the cap and moving the centreline .8mm into the block is the minimum for full surface contact between the cap and bearing shell- and if going this way that should be the target--

This would ,as you say, mean that the front of the g/box shaft is .8mm higher (out of line)(although it probably wasn't dead in line anyway) Although it's not much and the bellhousing probably isn't the most acurate fit anyway it'could' be enough to make it want to pop out of 4th gear but I doubt it-
If there was enough movement in the bellhousing bolts to lift it a tiddle it would adjust that
------------------------
If shimming,
A 0.004" shim would possibly be better than a 0.1mm metric shim (0.0394") just to get as much crush as possible--??

willy
William Revit

sorry---should read 0.00394"
William Revit

Dear friens around the earth,
You area very nice community. Thanks to all who are interested on my problem.
I think that I will find a solution next year: shims or copperplating by galvanise or building of individuel bearings. I found a machine shop who can make white metal bearings. Very interesting too is the advice from Winfried for metal coating.
To all of You I wish Merry Christmas.
Klaus


Klaus Harthof

Klaus
Just in case something comes up, are your crank journals standard or have they been ground---if so what size---??
Merry Christmas
willy
William Revit

Klaus
Just in case something comes up, are your crank main journals standard or have they been ground---if so what size---??
Merry Christmas
willy
William Revit

Willy,
the main journals are ground to first undersize. I measured 51,75 mm.
Some minutes ago I got an offer that it is possible to coat the main bore in the engine bloc including the caps with cold metal for 500 Euros. After that you can bore again with the right size (56,34 mm).
I think I will decide that next year because now I will habe quiet Christmas time.
Kind regards
Klaus



Klaus Harthof

Klaus,
Hard chroming the outer face of the bearing shells would be a lot cheaper.

Regards
Declan
Declan Burns

Hi Klaus,

My brother has recently sold his TF and still has a spare block. It has been converted to a lip seal at the back. He will sell it for £100 and place it on a pallet but you would have to arrange for a courier to pick it up from Lancashire in the UK.

Jan T
J Targosz

Jan,

If Klaus is not interested, Can you put me down for this block. I want to build a spare supercharged engine for my TD

John
J Scragg

Jan,
I Take it!
Write me address and account. I Think I organise the transport imediatly beginning next year
Is it an XPAG or XPEG? Round or oval waterholes?
Thanks for Your help!

Klaus

Klaus Harthof

Good news for Klaus - the forum is so much helpful.
W_Mueller

This thread was discussed between 17/12/2018 and 21/12/2018

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