Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - 1500 Block or Free Advice

Well, my bad news took a turn ofr the worse today as my original 1500 block was pronounced unrebuildable. The center main journal on the block is too far gone and the motor cannot be align bored. It makes me wonder if it was that way to begin with when originally align bored in 2003. No way to tell that I guess. So, I am starting to look for a donor 1500 block. As for the free advice, I guess I need to decide if this warrants a motor upgrade to a 1600 or 5 main 1800 since the car will no longer have its original block. Seems unethical to me to take a donor block and put the original tag in place. I expect that there will be varying opinions on this board and I'm not trying to start anything.... Thanks for letting me pout.
David Holmes

Gday David,I was told my 1600 block was a throw away by one engine rebuilder only to have another say it was easily fixed.Have other rebuilders pronounced your unrebuildible? If keeping the car original is important to you make some phone calls. Two cents Bob

Thanks Bob, I'll take that free advice.
David Holmes

If the second opinion shop also pronounces the Block unrebuildable I have a line on a donor block but my mecanic says after all is said and done it would be equivalent to a 1622... Have any of you done this? I didn't know that was even possible. If this is true are there disadvantages like overheating, or weaknesses created by boring the cylinders that far oversized?
David Holmes

After I wrecked my engine block following a broken con rod I obtained a used 1500 block. I now know that you aren't supposed to do it but in my ignorance I decided that as it needed a rebore I might as well take it out to 1600. The only pistons I could find at the time were +30 so I had the block bored to suit. That makes it about 1622cc.

It has an early MGB cylinder head which with the pistons being the high compression ones makes the compression ratio about right. I did calculate it at the time but have now forgotten what the result was.

That was in 1998 and the engine is still going strong (says he grabbing every bit of wood in sight).

I might just have been lucky.

Malcolm Asquith


I understand your sentiments. That said it has always been a bit of guess work which exact engine number was supplied with each car. Unless you have had the car from new or have a proven provenance, can you be sure that the engine number you have was original to the car? Could the previous owner have been unethical and re-tagged a replacement engine? Very difficult to answer in most cases.

My 1800 5-bearing late MGB engine has a number from a Sherpa van's broken engine. In a few years will anyone be any the wiser? Unethical, yes. Will it make any difference? In the shrouded mists of future years probably not.


Steve Gyles

Second opinion machine shop says the engine is rebuildable if we build up the bearing caps and then mill to provide the tolerances for a line bore. Opinions?
David Holmes

Build up just the caps, or the block halves as well?
Art Pearse

Gday Dave, good to hear you had a win. I asked the second engine rebuilder (he is 72)if he would work on your problem.He said the same method as your second machine shop and it would be a easy fix. Maybe some of the skills are not being passed on. Good luck with it Bob Just saw Art's post caps and block

I was told you can't build up the block halves as it is cast metal. I have decided to go with a donor 1500 block and be done with it. I can use my pistons and rods. It seems to be a more sure rebuild this way. Thanks for all the advice.
David Holmes

This thread was discussed between 11/07/2011 and 15/07/2011

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.