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MG MGA - 18G and 15GB similarity

You should have fun with this one.

I am restoring a 58 MGA. The engine is seized. I am considering switching to a 18G engine. I have found an 18G block.

I know the 18G and 15GB engines were very similar, but not sure just how similar. The big question: Which parts from the 15GB engine will work in the 18G block?

I don't want to buy the 18G block, and then find that a few parts are not interchangeable and also hard or impossible to find.

I wonder about things like the connecting rods, flywheel, pulleys, gears. I don't know what I don't know.

I plan to use the original 1500 transmission.

Any help or guidance is appreciated!
Chet Harter

Not a lot. Although they look the same the detail differences are quite big
Dominic Clancy

You can buy a complete 18G engine for a few hundred dollars. Then put the MGA carbs, generator, etc onto it and no one will know the difference unless they know what to look for.
Steve Simmons

Crankshaft main bearings are different, so crankshafts are not interchangeable.
barneymg

What Steve says is correct, but you will have a major performance benefit with the 1800 engine over the 1500 (it produces quite a lot more power). The later 1800 engines are even better and smoother, and all details to fit one using the bits you have from your 1500 are available on mgaguru.com
Dominic Clancy

The later engines are a bit stronger, but I've found that the early engines not only look correct and allow you to retain the mechanical tachometer, but they also seem to rev easier. Personally I consider a 3-main 1800 a plus on any MGA, but a 5-main late MGB a huge minus. They have a different feel, and the 5-main just doesn't look or feel right to me. Personal preference of course.
Steve Simmons

This thread was discussed between 01/02/2020 and 04/02/2020

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