The 22G1337 housing that came with my Mk 2 S is quite badly damaged around the starter motor opening. I have a very good condition 22G1921, which is vented. Apart from the venting difference which is obviously easy to fix, the only difference appears to be the piece of casting above the primary gear on the 1337 - something to do with oil movement? Is it OK to use the 1921, or should I try and chase up a 1337? Thanks Graham

it's OK to use the 1337 - the extra bit of casting is to stop the primary gear throwing oil up the breather

regarding the breather, don't block it up, use it - 1275 motors need all the breathing they can get

it's obvious, but maybe overlooked - you absolutely positively must fit a new outrigger bearing into the 1337 and on the 1st motion shaft, don't attempt to mix and match outrigger bearing inners and outers

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did I tell you that I won a trophy?

22G1337 dates from 1968. 22G1921 dates from 1979. Apart from the baffle (which appears to have been deleted from the later part), the only difference are in details of the casting "to assist in metal flow". Both parts come in vented or non-vented forms with a slight change in part number to distinguish them.

The venting (if you are using the diaphragm operated PCV valve) is important and (I think we all discussed this a while back) it is essential that no change to the original crankcase sealing be made for the valve to work properly.

From my memory of sorting out mine there might be a few more differences:

The drop gear bearing size changed a few times. If yours is a 3 synchro now it'll be a different size to 4 synchro
Later rod change ones have an extra piece on the casting. I can't remember if this causes an issue for remote change

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It's a good point. Both 12G1337 and 22G1921 have the larger 1 1/16" idler gear bearing. The later one has the "baffle" up on the top of the casing such as shown in timmy's picture. It also has the extra piece down the bottom which I didn't notice.

(with these drawings, they don't actually list any of these differences and you have to "spot the difference", often by overlaying one drawing on another - which each drawing says you should never do "drawings must not be scaled". This has caused me some problems because, in the case of 3rd motion shafts they changed the dimensions of some parts by changing the actual dimension on the drawing but didn't redraw it to the new dimension).