1275cc to 1380

Any topics pertaining to the BMC A-Series engine.

1275cc to 1380

Postby Paul McGuffin » Sat Feb 07, 2015 5:21 pm

It has a later sprite 1275cc engine that has been built into a 1380cc powerhouse.

There is a Bugeye on eBay up for auction. The seller states that it has a newer 1275cc that has been built up to 1380cc. Are there any problems by doing this, such as over heating, blowing head gasgets, etc.?
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Re: 1275cc to 1380

Postby Charlie Tolman » Sun Feb 08, 2015 12:39 am

The description of the Bugeye on its eBay listing has the car built with some good parts.
The statement about the Panhard rod is not correct.
However, there is a lack of information about the 1380 cc engine. A prospective buyer needs to know the journal sizes on the crankshaft, the type of connecting rods, type and brand of the pistons, camshaft name with duration and lift values, cylinder head status including valve sizes, static compression ratio, flywheel type, clutch style, and the list goes on - - - - - .

A 1380 cc Sprite engine requires some careful re-positioning of the cylinder bores in the block, with an offset boring technique. I do not know if this might cause head gasket issues.

Perhaps some of the forum readers / contributors can comment on overall considerations and possible issues associated with a 1380 cc engine.

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Re: 1275cc to 1380

Postby Paul McGuffin » Sun Feb 08, 2015 11:17 am

A 1380 cc Sprite engine requires some careful re-positioning of the cylinder bores in the block, with an offset boring technique.

I think a stock 1275cc would be more up my alley. Before hopping up a 1275cc, I think I would just put in a Datsun engine to match the trans he has.
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Re: 1275cc to 1380

Postby hpmowog » Mon Feb 16, 2015 4:48 pm

To go to 1380, you do not have to offset bore the cylinders. The pistons for a 1380 are 73.5mm. The next step up is 74mm pistons which increases the displacement to around 1400cc. To use the 74mm pistons, you do need to offset bore. That being said, it's a good idea to offset bore as there is just barely enough surface left on the deck (between the #2 and #3) on a 1380 block to land the head gasket and the cylinder walls are getting really thin too. Also, if you get some cylinder wear at 73.5mm and you haven't offset bored the cylinders, and you want to rebuild the block, your only option will be to sleeve it.
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'60 Bugeye - Vintage Race Project
'65 Innocenti S - Vintage Race Project
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Re: 1275cc to 1380

Postby Paul McGuffin » Mon Feb 16, 2015 9:39 pm

I see the eBay 1275 Bugeye we’re talking about sold for $22,500 today , Feb. 16, 2015
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