• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)
Tips
Tips

General Tech Crank bearing cap broke...Torque??

rooster

Jedi Trainee
Offline
After replacing the trust bearings on the crank, while torquing down the main bearing the bearing cap broke. :sorrow:

I had my torque wrench set to 65 lbs as per the manual.

So is the manual correct?

What did I do wrong?

How do I go about getting a new bearing cap?

Is it something that requires machining?

Thanks
 

TR3driver

Great Pumpkin - R.I.P
Offline
Man, that sucks!

I don't know of a source for a new main cap; and yes, it does require machining. Easier to start looking for a used block (with caps).
 

CJD

Yoda
Country flag
Offline
Once you have Marv’s new cap, you will need to look around for a machine shop that has a line bore machine. They will grind a few thousandths off all your caps, and then re-bore the main bearing bores into perfect size and alignment. Price it ahead of time, because it may cost more than a decent used block.

That is a first, too. I have never heard of a cap cracking. Could you post a pic??
 
OP
R

rooster

Jedi Trainee
Offline
@ Marvin...It's a 76 TR6. The one that broke is the back one (with the thrust washers).

Is it possible that I put it on the wrong way around? I had put new thrust washer (std and .005 over) and new standard bearing. I used some moly grease on the bearing and thrust washer since I'm in the middle of a frame off resto, and it will be a while before I get the engine running again. I'd really like to know what I did wrong, so I don't do it again!

Ok, looking at my options...Lets say I go with a used block. Does one transfer the parts over from the original engine, or just do a rebuild?

Other option is as stated above, get a used cap. I guess I have to get the block line bored. To get that done, I guess I have to remove all the parts (crank, pistons etc.) from the engine?
 
OP
R

rooster

Jedi Trainee
Offline
Oh, I'll get a pic posted tomorrow.

I'm also going to double check the size of the crank bearigs, maybe I got sent the wrong size.

Thanks guys for your help!
 

glemon

Yoda
Country flag
Online
I am by no means an expert on this, but did learn by doing once that if you don't put the bearing cap on the same way it came off (180 degrees out) it can cause the crank to bind, so maybe that was your issue. The last rebuild I did I got one of those machinist numbering sets where you hit the one end with a hammer and the other end imprints a number on the part. I marked all the bearing caps and corresponding surface on the block with matching numbers so there would be no confusion on reassembly.

As others have said getting replacement parts to work right will be more than a mere bolt on. Good luck.
 

glemon

Yoda
Country flag
Online
Also spin your crank as you tighten cranks past snug (pre lubed of course) the motor will tell you if something is going wrong (obvious resistance beyond mere tight clearances)
 

TR4nut

Yoda
Country flag
Offline
A friend of mine broke the center cap on a TR3 engine, It was installed with the right orientation but it accidentally became wedged before seating and snapped from the stress of bolting down. We tried several spare caps from broken engines and it was surprising the variability seen in the different parts - he found one that was close and the machine shop line bored the best one to fix. Unfortunately the advice you've already received about finding a replacement block may wind up being the cheapest solution.
 

CJD

Yoda
Country flag
Offline
You are correct, in that the engine will have to come apart to repair. Even the oil passage plugs, since you will get metal in the oil passages from the boring operation.

It would always be best to rebuild any used motor you find too, unless it was already rebuilt by someone you trust. I would lean towards using your parts in the new block, simply because you know their history. An engine that is running well is rarely pulled from a car...so chances are something is off with a used engine. Fortunately most problems are with the moving parts, so blocks are normally in good shape.

I would really be interested in seeing pics of the crack, from both sides of the cap. I hate to guess what could have caused it until I see where it happened.
 
OP
R

rooster

Jedi Trainee
Offline
Here it is:
crack.jpg

from another perspective:
block.jpg

the bearing:
bearing.jpg



 
OP
R

rooster

Jedi Trainee
Offline
I'm going to get a quote from a machine shop or two to get an idea of how much the line bore will cost.

Also since I've worked so hard at breaking the bearing block I should reward myself by getting an engine hoist and stand.
 

CJD

Yoda
Country flag
Offline
I think the bearing insert pic says it all. Some FOD was on the crank when you were tightening the cap. Perhaps a bit of the old thrust bearing? Hopefully it was only soft metal material, so it didn't hurt the crank bearing surface. Be sure to spin the crank and look closely for corresponding damage. The good news...at least that means there is nothing inherently wrong with your block or original cap.
 
OP
R

rooster

Jedi Trainee
Offline
FOD?

I am thinking that it was oriented the wrong way round. It's not as evident in the photo but the side of the bearing is flattened out. When I put the new bearing on I checked and cleaned the surfaces to make sure there wasn't any dirt or what not. Also when inserting the new upper bearing around the crank it was difficult to do, I had to wiggle it about a lot. Maybe there was something in there, but the old upper bearing didn't look like it had fallen apart.
 

Geo Hahn

Yoda
Country flag
Offline
I'm going to ask something and please don't think I am an idiot (or you may think so, but spare me hearing it):

I look at that break and wonder:

attachment.php


Could JBWeld save that part?

Intuitively it seems that the mains are under much less stress than the connecting rods -- in fact I think the idea is that with good oil pressure the crank is not touching the bearing surface.

I think there is some 'whipping' or whatever you call it at certain high RPMs so maybe those forces rule out such a ghetto repair... but thought I'd bring it up.
 

JerryVV

Jedi Warrior
Offline
Geo, I don't think you're an idiot, not at all but ask yourself, would you put an engine together with a JB welded main bearing cap? I don't think you would and I sure as heck would not. Beyond that I doubt that with JB weld you could maintain any tolerances. Too much risk, what's that noise? Is that the cap I glued together or worse was that big bang I just experienced because of the cap I glued together? Why did I do that? Also as he mentioned it's the cap with the thrust washers so it's resisting the clutch pressure every time the gears get shifted.
 

charleyf

Jedi Knight
Bronze
Country flag
Offline
In truth JB WELD is really as Jerry calls it GLUE. It is not a weld. Keep that in mind when using it.
Charley
 

CJD

Yoda
Country flag
Offline
FOD?

I am thinking that it was oriented the wrong way round. It's not as evident in the photo but the side of the bearing is flattened out. When I put the new bearing on I checked and cleaned the surfaces to make sure there wasn't any dirt or what not. Also when inserting the new upper bearing around the crank it was difficult to do, I had to wiggle it about a lot. Maybe there was something in there, but the old upper bearing didn't look like it had fallen apart.

Foreign Object Debris. Something really squished that bearing insert at one spot. There had to be debris in there to do that. The debris lifted the cap slightly off the crank, and then the bolt placed a teeter totter action over the debris spot. Sorta like when you snap a stick over your knee to get leverage. The debris would be your knee.
 
OP
R

rooster

Jedi Trainee
Offline
Foreign Object Debris. Something really squished that bearing insert at one spot. There had to be debris in there to do that. The debris lifted the cap slightly off the crank, and then the bolt placed a teeter totter action over the debris spot. Sorta like when you snap a stick over your knee to get leverage. The debris would be your knee.

Thanks for the explanation.

I'm going to try and get a couple of quotes for the line bore. I'll post back here with the quotes. If not too expensive I'm leaning towards keeping my block if there is no other damage and getting it machined, as I know where it's been the last 23 years, and it has been solid till now.
 
Similar threads
Thread starter Title Forum Replies Date
G Cannot get my upper crank bearing shell to budge.. Triumph 12
nichola TR6 Door handle and window crank installation Triumph 0
D TR2/3/3A TR3 throttle linkage bell crank. Triumph 13
R Wanted 3 main crank MG Classifieds 1
Twit early TR4 Crank Handle wanted Triumph Classifieds 0
P TR6 Tight window crank Triumph 9
71TR6 Triumph TR4 Coventry Radiator with crank hole- recently refurbished Triumph Classifieds 0
D TR2/3/3A TR3A Crank Dog Triumph 2
K TR2/3/3A The timing mark on the crank pulley.... Triumph 5
K For Sale Starter Hand Crank Triumph Classifieds 0
J 1275 EN40 Crank Spridgets 5
J TR2/3/3A Flywheel-Crank Dowel Alignment Triumph 6
R TR2/3/3A Extension Crank Bolt Attachment Triumph 12
M Wanted TR3 Hand Crank Guide Triumph Classifieds 3
Alfred E. Neuman TR4/4A TR4 fan extension and crank bolt length Triumph 9
D TR2/3/3A Crank handle support Triumph 11
Got_All_4 TR2/3/3A Hand crank misalignment Triumph 9
K For Sale TR3 crank handle Triumph Classifieds 0
M Wanted TR-3 Crank Handle Triumph Classifieds 3
R TR2/3/3A Temperature Gauge for 1954 TR-2 & Hand Crank Triumph 17
Got_All_4 TR2/3/3A TR3 engine hand crank Triumph 14
ckeithjordan Wanted WTB: TR3 Crank Handle Guide Stays Triumph Classifieds 1
Drone Dog BT7 tri-carb installing my crank Austin Healey 4
Rut Crank/flywheel dowels Spridgets 3
R TR2/3/3A One more crank pulley question Triumph 7
R TR2/3/3A Crank pulley question Triumph 4
GTP1960 TR2/3/3A Timing cover/crank hub oil seal Question Triumph 4
Boggsy64 MGB Crank doesnt turn freely - new main brgs MG 21
jfarris TR2/3/3A TR3 tining without marks on crank pully Triumph 6
T Replacing the crank pulley/damper Austin Healey 4
T TR4/4A How to determine if the crank is good before pulling the engine out Triumph 8
R Crank damper alignment Austin Healey 6
R timing gear crank shims Austin Healey 11
R Dennis Welch Rear Crank seal conversion - Gap in back plate Austin Healey 19
R Engine crank shaft nuts Austin Healey 1
B Remove Crank Nut Austin Healey 55
M_Pied_Lourd TR2/3/3A Crank Oil Slinger Orientation Triumph 2
S TR4/4A Water pump and crank nose questions Triumph 7
GTP1960 TR2/3/3A Removing the fan extension from the Crank hub Triumph 13
T TR2/3/3A How many guide holes in TR3 flywheel for crank pin? Triumph 2
M Crank Pulley Removal Austin Healey 12
J General TR Narrow Belt crank pulley Triumph 0
T TR4/4A Oil drain hole from rear crank seal/rear main cap Triumph 3
K TR2/3/3A Su carb rod linkage bell crank stud? Triumph 6
CJD TR2/3/3A Crank balancing Triumph 11
B Chip off the crank pulley Austin Healey 12
HJR TR2/3/3A Crankshaft crank bolt head[108498] Triumph 10
jaegzie Size on head on end of crank Spridgets 1
Scotsman TR2/3/3A Crank Pulley Triumph 2
Geo Hahn TR4/4A Crank Bolt Size Triumph 5

Similar threads

Top