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help with engine ID

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M

mightymidget

Jedi Knight
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My $500.00 Midget has a knock in engine and was going to rebuild but got to thinking I would jerk the engine out of Bugeye I am restoring and install it into the Midget to save some bucks.

It is suppose to be a 1275 but looked at engine last night and someone has remove the engine tag. So before I go to the trouble of trying to get it running to check condition I would like to know if it is indeed a 1275.

Thanks
 
How bada knock? What about droppin' the pan and swapin' out bearings?
 
MM:
If it doesn't have tappet chest covers, then 99.44% it is a 1275. Might be something really strange in an in-line configuration if it doesn't have covers and is less than 1275cc's. There is a block casting number just under the oil pickup passage on the manifold side. It's on the same side as the cam and tappets. 948's usually have a big '950' cast into the side. 1098's usually have a '1100' tag pinned to the manifold side of the block just below the front cam bearing bore. If you don't have tappet chest covers, then the block casting number will be something like 12GXXXX. I'd have to look at some blocks, but there should be just two variants of 1275 Spridget blocks that made it to the USA. The 1967 thin flange variety and the 1968-1974 thick flange. Both are fine for the street.

There are other minute detailed differences besides the tappet chest covers. Small bore (948/1098) blocks are shorter by about 3/16" in length, have a more sculpted appearance, only have thin flanges, one freeze plug in the back, only one oil passage on the distributor side, a hole only big enough for the dipstick and not a dipstick tube. Could cite other stuff, but you get the picture.

If the engine has been knocking for a while, I'd worry about the roundness of the journal. Popping the pan will give you an idea of the damage and the remedy. I've seen knocks turn out to be 2 piece pistons, with a piston broken at the oil control ring slot.

HTH,
Mike Miller
 
I will check the casting numbers but in the Moss catalog (cylinder Head) what # would be the "Tappet Chest covers"?
 
MM:
Anything in-line and tappet chest (948/1098) would have cylinder head numbers:
2A628
2A629
12A185
12G202
12G206
12G295

There might be a real odd ball head number from a late model mini (998) on there, but probably not.

No tappet chest, 1275 would have cylinder head numbers:
12G940 (no emissions)
12G1316 (emission holes)

Again, there are transverse heads from the UK that could have been put there, but not likely.

The 1098/1275 casting numbers will be between the #2 & #3 rocker stands on 99.9% of the heads. 948 head casting numbers can be just about any where under the valve cover.

HTH
Mike
 
MM:

Thick flange 1275 block has casting #12G1279 as verified this morning at the barn.

I'll check a thin flange block tonight at the shop.

Mike
 
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