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MG MGB Technical - Length of Bolt main bearing cap

Hi, I have bought a set of Bolts from Moss (12B2356) for my 18V-engine (12H3503/AF3). When putting them in the block I feel that they are to long.They bottom before they should as I feel!

When taking the engine apart I found Studs/nuts instead of the Bolts I now have ordered.

The length of the Bolts are 75mm and I would be happy if someone could check if that is a correct length!

Happy for a quick answer! :-)

Anders / Sweden
Anders Dahlberg

According to the Moss website, that part number is no longer stocked.

Is it definitely an 18V engine? What is the number "12H3503/AF3"?
Dave O'Neill2

Hi Anders

I cannot measure yet for you. Have you tried assembling with and without the cap to see how many threads are spare?

Peter
Peter Burgess Tuning

Hi Dave,

Well the enginenumber says 18V, and the 12H3503, AF3 can be found on the the engineblock.

It's funny because on Moss Website it says NLS for 12B2356 and on Brown & Gammons Website it say use 12B2356 (Bolt) instead of 51K1482 (Stud).

And when I look in Moss catalouge it is the same number for the Bolt and the Stud, 12B2356! It is not easy every time! :-)

Anders
Anders Dahlberg

Hi Peter,

Well finally after many, many years the engine is coming together. I had hoped to get it all finished until letting you know the happy news! But I found this Bolt being to long. Without the washer I have at least 3mm left when the Bolt meets the bottom of the threaded hole in the block. And I dont want to fill the gap with too many washers, thats why I sent the question if I have a too long Bolt!

I haven't sent you any information concerning the Crossflow head from Andy. We hoped that we had solved the problem by finding the sidecover holding against the head from underneath. But when getting the new cylinder head gasket and trying to start the engine again we after a while got more water in the Sump! :-(

We have after that found a crack in one of the holes for a pushrod and also of what it looks a porosity or crack somewhere around one of the valveguides of cylinder two! Tomorrow we will hopefully test the cylinderhead with compressed air and soapwater! :-)

Best regards from Anders & Ingvar

" PS. Will come back to you with an order for an 123-Tune and your Roller Rockers!"
Anders Dahlberg

Hello Anders,

I don't have a measurement for you but I do have a warning. Some few years ago there was a very lengthy discussion here on exactly the issue you have (fortunately) discovered before trying to run the rebuilt engine. In that instance the owner had actually started the engine and discovered next to zero oil pressure.

The lengthy discussion covered the identification of the problem (too long a bolt substituted for the studs) and the solution. If I remember correctly, in that case, the solution was the addition of a hardened extra thick washer under the bolt head. That work was done under that car, sump removed.

I don't recall the thread title (time elapsed!) but seem to remember Peter Burgess was much involved in the solving of that problem.

Peter, is my memory any where near the mark?

Regards

Roger
R Taylor

Your memory is probably better than mine Roger

Anders, When I get back to work I will count the threads on a main bolt and measure the length of the bolt too.

Peter
Peter Burgess Tuning

Peter, Sorry, perhaps not correct re your involvement, but here it is:

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=71&subjectar=71&thread=2004062908580113819


(I'm sorry, for some reason that has lost its hyperlink quality)

Posted by: I D Cameron

On 29 June 2004

Title: Engine rebuild – Oil pressure issues

Regards

Roger
R Taylor

Ok, It has regained the linking!!

One of those days here - too hot I think.
R Taylor

Now I will retire, don't know what has happened to the link I tried to post. Will need to be searched on above details through archives.

Regards

Roger
R Taylor

Hi Peter and Roger,

I have read the thread from 2004, and others, and it is quite obvious that the bolts in my engine is a little bit too long.

I suppose that the best method is to use a couple of washers. Should these be of a certain quality? I believe that it is better to do this than putting the bolts in the lathe. Is it vital to use the lock tabs securing the main bearing bolts?

Anders
Anders Dahlberg

Anders,

I am quite certain that any washers would have to be hardened or they would crush and cause the bolts to come loose. If the engine is supposed to have lock tabs, I would not leave them out.

Charley
C R Huff

Hi Anders

I reckon we machined 3-4 mm off the bottom of the bolts. This is preferential to washers. You do not need lock tabs. If you are wary use a threadlock to lube the therads instead of oil then torque the bolts down....do a dry build first to be on the safeside ( knowing you this is what you do anyway).

Peter
Peter Burgess Tuning

This thread was discussed between 01/01/2013 and 03/01/2013

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