• 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

MGB Crank doesnt turn freely - new main brgs

Boggsy64

Jedi Hopeful
Offline
I need some advise on what may be an abnormal problem. I had my crank turned at the machine shop and my block fully dipped cleaned and tested. They turned the crank for .010" over and I installed appropriate brgs. Issue is that the crank is difficult to turn when in the block without any caps installed. I can get it to turn but not easily. When I install any cap the crank is very difficult to turn.
- I verified the clearances with plastigage and right on at approx. .00175".
- I am thinking the bearings themselves may be too large in diameter because there is wear on the bearings at the gap. See pics.
- the wear in the pics if from only several hand turns of the crank. The small one in JPG 336 had not been rotated with a cap installed, only cap installed for plastigage.

I have not assembled an 1800 before but other cranks turn very easily. this cannot be normal??? Crank bent?
 

Attachments

  • IMG_0337.JPG
    IMG_0337.JPG
    75.2 KB · Views: 30
  • IMG_0336.JPG
    IMG_0336.JPG
    77.4 KB · Views: 29
D

Deleted member 8987

Guest
Guest
Offline
What did the wear pattern on the old bearings look like?
You can tell a lot on teardown about issues you may need to inspect later.

You are absolutely certain the caps are set for the correct journal?
And not flipped around?

If they are right (bearing tabs same side usually) and numbers match, take the block back with caps (no bearings) installed, have them check the line with an inside caliper in standard places.

Did this engine run in your presence before teardown? Reason I ask is I have twice in 60 years had an engine brought in for rebuild...and when we got done, main caps were not for the engine delivered, and it was the only engine of that type in the shop.
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
TOC thanks for the reply. The motor did run and I drove it before teardown. I drove 2200 miles and used 22 quarts of oil, thus the rebuild..lol I have talked to the machinist and bearing supplier. Yes the caps were installed correctly. I was using 30 weight oil and have been recommended to use assembly lube which I am doing. I will try a few more things and let you know. Everything on paper looks correct.
 
D

Deleted member 8987

Guest
Guest
Offline
I would tell you to run it...but I have seen engines with bearing crush area swedged out that overheated the bearings, so best to check it further. Bore check on the line can't hurt, unless they did that.
 

Brinkerhoff

Jedi Knight
Offline
The bearings should be fitted to the block dry , then lightly oil and lay the crankshaft in. The crank should spin easily and almost effortlessly without the caps . If the crank is difficult to turn without the caps something isn't right with the block or crank. Did they provide the measurement to turn the crank undersize or did you?
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
The shop came up with the spec for turning to .010" undersize. It is a race shop and via plastigage (I know not the most accurate but don't have a bore gauge) it appears they got it correct.
 

Brinkerhoff

Jedi Knight
Offline
I think they would be able to tell if the crank were bent before they turned it and I don't think they could turn it if it was bent , so if its bent now it must have been dropped after it was turned. Or the block is suspect but they'll want to measure . I've rebuilt a lot of B series engines and can tell you I'm only surprised when it goes as planned. All the best!
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
Well the good news I used permatex super slick assembly lube and after all 5 caps installed the crank turns reasonably easily. It will not spin on its own with a shove, but turns smoothly and evenly. I installed some bolts in the flywheel end and used a screwdriver in these bolts to gently turn the crank as I installed each cap. I does seem to turn better with all 5 caps installed and tightened.
I guess I learned a few things
- 30 weight oil is not good assembly lube (at least for crank bearings)..use the real thing.
- I was told that the bearings are not fully round until torqued. I don't know if this is true but seemed to get better with more caps torqued?
- Using the plastigauge to verify the gaps makes me feel better.
As usual live, do, and learn. Hopefully I will not be inside the engine ever again...but you never know...
 
D

Deleted member 8987

Guest
Guest
Offline
And...all the Plastigage tells you is vertical. If the bore is squeezed narrow, you won't be able to tell with Plastigage...generally.

Wait until you open an old engine and find feather shims between bearings and block/cap.
 

Brinkerhoff

Jedi Knight
Offline
Any success or failure of an engine rebuild falls on the shoulders of the assembling mechanic , not the machinist or the parts supplier , so you're the guy . You're the one that has to make sure everything is clean and fitted properly and nothing can replace the "feel" it takes to assemble parts. If I wasn't confident that it was correct I'd take it back apart and clean and inspect the bearing shells for any sign of scuffing. Good Luck.
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
Thanks you guys. I agree it is up to me and I will be the one on the side of the road as well! It had been a long time since I installed a crank. The last was in my VW rabbit. I feel good about the crank now and these engines are mighty tough. During the 2200 mile drive from Arizona where I picked the car up from my dad, I actually ran for about 60 miles, thru the deep desert of New Mexico, with dropping oil pressure. For about 30 miles the pressure was basically zero! In that desert between El Paso and Carlsbad there is nothing...I mean nothing and no one. I kept expecting some life over each hill but it was not happening. He had told me before I left Tucson that I should carry a gallon of oil with me. I thought he was pulling my leg. Turns out he was right!
The block was basically empty but after filling with oil I made it the rest of the way to North Carolina from Carlsbad, NM using 22 total quarts of oil. Even though the motor was pretty worn, it amazed me how tough it was. I guess some leather bearings might be OK!:D
 

Rut

Obi Wan
Silver
Country flag
Offline
I've had problems with a stiff to turn crank on a couple of rebuilds and my machinist/engine builder just hit it with a rubber mallet and it spun freely. Sometimes things don't seat completely and the plastigage will show good clearance, but you'll experience the problem you did.
Good luck, Rut
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
Next questions similar topic. I am having a hard time with piston rings, particularly super thin oil rings above and below the expander ring, popping out of the ring compressor and immediately snagging on the chamfer at the top of the cylinders. I am getting a better compressor than the cheapie I had but any thoughts? Also do you really need to check piston ring gap with a new set of rings? Seams like a lot of work but I would expect the rings to be right???
 

Rut

Obi Wan
Silver
Country flag
Offline
Easy to check piston ring gap...insert ring in cylinder and push it down with the piston, measure with a feeler gauge. As far as using a ring compressor goes you need the lube the cylinder, lube the ring compressor and/or piston assembly, insert the piston in the correct orientation and give it a quick rap with a rubber hammer handle using enough force to drive the piston into the bore. Make sure you protect the crank from any bolts/studs on the con rods with rod bolt rubbers. What brand of rings are you using?
Rut
 

Brinkerhoff

Jedi Knight
Offline
Yes , checking the ring gap is a must. Be thankful if you find one too tight now. I use a corrugated type ring compressor and you can tighten it down more than you think. The piston shouldn't rock at all after its tightened down . Hold the compressor tight to the block ,then as Rut said tap the piston / rod in with the wood end of a hammer or such. Be careful of the other end as it clears the rod throw of the crank. Do not move the compressor until the piston is all the way in. There is ever so slight of a chamfer at the top of the bore to assist but you must hold the compressor firmly down to the deck of the block.
 
OP
Boggsy64

Boggsy64

Jedi Hopeful
Offline
I understand to check the gap at the bottom and top of the bore to check for taper, but is it sufficient to check one ring and assume the set is good, or every ring?
 

Rut

Obi Wan
Silver
Country flag
Offline
Yes that's the idea to check for bore taper and I'd check every ring , once you're set up , it doesn't take long.
Agree on this...check every ring in the bore where they will live, top, middle, and bottom. After going this far the last thing you want is for one ring or one bore to mess you up! Also don't use anything more slippery than engine oil on the bores/pistons or the rings may not seat.
Rut
 

Patrick67BJ8

Darth Vader
Silver
Country flag
Offline
I had one engine that the main studs were tightened so much that the main walls had hairline cracks in them that when the studs were tightened it caused those walls to push out, which is towards the crankshaft, causing the binding. Easy fix, weld and the line bore the mains.
 

LarryK

Obi Wan
Gold
Country flag
Offline
Correct thrust washers? Had this on a 4.2 Jag, was given to wide washers.
 
Similar threads
Thread starter Title Forum Replies Date
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
R General Tech Crank bearing cap broke...Torque?? Triumph 37
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
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
PatGalvin TR2/3/3A TR3A Crank pulley removal Triumph 9

Similar threads

Top