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When I tighten the the main bearing caps the crank is stuck

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arnolda Avatar
arnolda Arnold Adams
Vancouver, WA, USA   USA
This may be a long shot, but, will mention it. I recently sat in on an engine rebuild where the same result happened (crank did not turn after torque),

It turned out that one of the new bearings was marked incorrectly and was too thick.. The mechanic and a local machine shop had never seen that before!

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jmac Avatar
jmac Silver Member Jere McSparran
Greenup, IL, USA   USA
1978 MG Midget "Therapy"
1978 MG Midget "(SOLD)"
In reply to # 3678022 by arnolda This may be a long shot, but, will mention it. I recently sat in on an engine rebuild where the same result happened (crank did not turn after torque),

It turned out that one of the new bearings was marked incorrectly and was too thick.. The mechanic and a local machine shop had never seen that before!

Nothing would surprise me anymore. These bearings come all wrapped in the same cellophane, but I've not seen the factory to know if that is even possible.

X3 on the tang to tang, I should have mentioned that. The direction of the cap can make a difference.

All of this should give you somethings to look at when trying to figure out why your bearings and caps are binding on the crank.

You ARE using an assembly lube, correct.



JMac
JMAC Engine Shop
http://www.jmacengineshop.com

MC-5C Brian Evans
Tatamagouche, NS, Canada   CAN
First off, you can't measure end float until all the caps are in and torqued, so make sure to do that again. As said, make sure the caps are on the right way. Put them on one at a time and torque each one to spec by itself, you will find out if all the clearances are tight or just one cap. If they are all tight, you have the wrong bearings or the crank was ground wrong. The proper way to measure clearances is to use a bore gauge and a mic, but you can do a rough check with a caliper if you are careful, and of course plastigage. When you lay the crank in you can spin it and check to see if it's bent with a dial gauge on the center main (with the center main bearing out, just bearing shells in the block in 1 and 3. All this is part of a dry build, btw, which you do to check all this stuff before you assemble the bottom end for the final time.



Brian Evans, Tatamagouche, Nova Scotia
1961 MG Midget G-AN1-L218, 1964 Mini Traveller, 1979 MGB LE Canadian edition.

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
The correct way to measure crankshaft endplay is to snug down, but do not torque, the main cap which carries the thrust washers, in this case, on a 1500, that would be the rear main bearing cap. On A and B series engines it is on the center main cap.

A step that is often omitted is "centering the thrust." Despite the presence of the main bearing bolts or studs, there will always be a slight bit of clearance between the bolt/stud and its hole in the main cap. As such it is possible for the thrust main, indeed all the mains, but most especially the thrust main, to not be perfectly perpendicular to the crankshaft. This clearance can be enough to affect the reading of the crankshaft endplay.

With the non-thrust mains just hand tight, and the thrust main only slightly tighter, one should use a soft-faced dead-blow hammer to drive the crankshaft fore and aft. This will force the thrust main to square with the crankshaft, and the thrust washers as well. In this condition, you can torque the thrust main and measure crankshaft endplay accurately.

This procedure is especially important on the 1500 engines, which tend to eat thrust washers...


Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

oleanderjoe Avatar
oleanderjoe Gold Member Joseph Baba
Fresno, CA, USA   USA
1500 "MIDGET / SPITFIRE" That is, CORRECTOMUNDO. (Not 1500 MGA)


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oleanderjoe Avatar
oleanderjoe Gold Member Joseph Baba
Fresno, CA, USA   USA
End Thrust. Dick is right, SNUG them down. I find it is also best to Smack the end of the crank with my Big Lead Hammer to pick up any clearances in the Main Caps and Bolts/Studs "BEFORE" taking a measurement Sometimes you can pick up a Thousand or Two. It is amazing how much clearance there is between the parts. Cheers


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tomshobby Avatar
tomshobby Tom Smith
Windsor, WI, USA   USA
When I had my TR6 engine done some 10 years ago my builder found one pair of mains were stamped with the wrong size and it turned out it was mismatched at the factory. That was more than 60k miles ago and all is still good.
I suggest checking them all with a mike and plastigauge.



Tom Smith
1974 Midget
1976 TR6

GeorgeOhr Nonya Business
Yes, confused, USA   USA
In reply to # 3678129 by oleanderjoe I find it is also best to Smack the end of the crank with my Big Lead Hammer


Beat-to-Fit, Paint-To-Match!

When it doesn't fit, use a bigger hammer! grinning smiley

trowe9 Avatar
trowe9 Gold Member Tracy Rowe
Baxter Springs, KS, USA   USA
The main bearing caps are now confirmed to being turned the right direction and in the right order. All is good until I torque the front main bearing and then it will turn only with a pretty good amount of effort. I visited with Hap and he suggested I have the crank checked to insure it is straight and to check the diameter and inside diameter of the bearing. Hopefully I will get that done tomorrow and I will find my problem. Thanks again for all the help and I will let you know what I find.

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