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MG MGA - Dimension needed - MGB flywheel or clutch cover

Anyone good with accurate measuring? I need the distance from center of one of the MGB alignment pin holes to center of the nearest bolt. You can get this from any MGB flywheel or clutch cover (I don't happen to have a spare in my possession at the moment). This needs accuracy within a few thousandths of an inch, as I want to put it on a flywheel machining drawing.

See pictures here:
Barney Gaylord


I can't measure a flywheel as my spare engines aren't here, but I do have a clutch cover.

There are two dowel holes on my clutch cover. The distance between the centre of the bolt and the centre of the first dowel hole is .609" and the distance between the two dowel hole centres is .689"

Hope that helps.
Dave O'Neill 2

Got it. I also have results from a couple other sources. With my engineering hat applied, I conclude the design dimension is exactly 7 degrees rotational displacement from bolt to pin, which works out to 0.603 center distance. Clutch cover pin hole is 0.003 larger than the pin for accurate alignment. Clutch cover bolt hole is up to 0.040 larger than the bolt to have lots of positional tolerance for the bolt hole to be punched.

If anyone is interested, I have updated my web page here:

Barney Gaylord

A bit confusing.
Does not your clutch cover have three dowel holes if it is for a MGB?
The MGA clutch cover has two dowel holes.
How can the distance between two dowel holes be .689" when they are 120 degrees apart?

M F Anderson

Check this image:

Jim Ferguson


My comments still apply to Dave's posting to which I am referring.
Why does the clutch cover have only two dowel holes if it is supposed to be a MGB clutch?
Where do you get a distance between dowel holes of .689"?
I have just done a MGB clutch conversion in a mga twin cam and I cannot understand the comments in Dave's posting.
I am happy with Barney's article, it is correct.

M F Anderson

Sorry, I didn't make my self clear. There are actually two dowel holes adjacent to each bolt hole, giving a total of six.

I don't know why. Perhaps the flywheel dowels were moved at some point and the replacement clutch covers were made to accomodate both scenarios, or maybe the clutch cover is the same for another make/model of car.
Dave O'Neill 2

Here's a photo...

Dave O'Neill 2

Consider this. First alignment hole .603" from the bolt hole is 7 degrees rotation around the center axis. Second alignment hole .689" from the first is another 8 degrees rotation, making the second alignment hole 15 degrees from the bolt hole. I recon it is for a different application, but have no idea what. My first thought was that the extra holes may have been tooling holes used to align the part on various jigs and fixtures during the manufacturing process (stamping, drilling, balancing, assembly, final balancing).
Barney Gaylord

This thread was discussed between 10/02/2011 and 12/02/2011

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