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MG Midget and Sprite General - 1970 Midget / engine

Yesterday I purchased a 1970 MG Midget and took it home.
The chassis number is GAN5UA/80561, with a build date of 12-69. The engine number is 12V671Z-L16546.

I can't find that engine number in any manual that I have.I have looked in the Bentley, Haynes, and Moss books. I have had several MG's in the last 40 years, but they have always been in the 60's or earlier. Can someone please give me any information on that engine number?
Joe
North Carolina
USA
J. Muncy

I just found a German MG forum that refers to a 12V671Z

<<It is, however, a # '74 U.S. model with low-compression engine (12V671Z).>>

Your car may not have its original engine, but it would appear to be US low-compression (L) 1275 Midget engine.
Dave O'Neill 2

What are the +'s or -"s of a low-compression engine?
What octane fuel should I use after I finally get it running?
J. Muncy

the "regular" compression ratio was 8.8:1

the low compression engines ('72 ~ '74, for the US market) were 8:1. They used dished pistons to increase the area in the combustion chamber.

lower compression engines are more forgiving of low octane fuel

If you've got a '74 engine in your car, those pistons, and the distributor advance curve (if your engine still has its original one) will be the only things worth noting that are different from what would have been originally fitted in your car. Oh, maybe the paint color (what year did they change to black?, I always thought it was a yucky color for a freshly rebuilt engine), but that's not hard to change during a rebuild! I can't remember if there was any difference in the oil pump drive, but there is one other difference, the crankshaft was not tuftrided in '74, but that hasn't seemed to make much/any difference in the longevity of '74 engines, so ought not to matter much to you, I think.

Norm
Norm Kerr

Dave and Norm,

Thanks for the information on the engine. As I said in my first post, my manuals have no mention of a low
compression engine. The car has a very nice solid body, with all of the lights, bumpers, and chrome taken off to check for rust. It also came with many new parts for me to install.
Joe


J. Muncy

I know what you mean about it being a challenge to find in the manuals, it is kind of buried in the Bentley manual, on page 361 of part 2 of the Appendix:

http://www.spridget-tech.com/service_manual/Part-3-25-56.pdf

Sometimes it amazes me how much information is in that manual, but it sure does take some work to use it effectively.

Norm
Norm Kerr

Norm,

I found it, right where you said it would be. Thanks.
What part of Michigan are you in? I lived in the downriver area, just below Detroit for 42 years, (Wyandotte and Trenton).
This is my fifth Midget that I have owned, but none of the other ones was this far taken apart when I purchased them.
Joe

J. Muncy

Your rear wheel seems to stick out a long way. You may have a steel-wheel axle casing which has had wire-wheel halfshafts fitted. The steel-wheel axle is wider.
Dave O'Neill 2

Dave,
I just looked at the car, I guess when the previous
owner installed new bushings, he didn't try to center the rear end assembly. It sticks out on the one side, almost 3" in on the other. Thanks for pointing that out.
Joe
J. Muncy

Hi Joe,

I'm in Ann Arbor. If you're ever back in the area let me know.


Norm
Norm Kerr

Lower compression is better for supercharging or turbocharging. Make sure that everything is in tip top shape before putting a blower in.
S.A. Jones

This thread was discussed between 28/04/2011 and 06/05/2011

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