Got what I think is a 1300 engine with a cade which doesn't seem to be an original VW code D1300751.



It's a bit of an oddball. Has twin port heads, a canister oil filter via a Scat (I think) take off from the pump, a 30hp fan with a hole cut in it behind the oil cooler rather than a doghouse.
Looks like the engine has had the pistons off as they still bear markings showing which cylinder number and orientation.

It looks as if a later D code (ie 1200) case has been used to build a bigger capacity twin port engine, quite common as 1200 cases tend to get pounded and abused less than bigger cc units.

Usually got single relief valve set up but but they can work well as long as you don't go too wild capacity-wise.

Yep it`s a "mix up" of parts. D code is a 1200cc / 34HP descriptor

Measure the stroke to see if it still has a 1200 crank in it. 1200 is 64mm, 1300 and upwards is 69mm. 1,200's have different little end bearing sizes, so can only be turned into 1,360 with aftermarket kit's. A 1,300 crank is universal for all larger engines and it's main bearings are the same size as the 1,200's, so a straight swap into a 1,200 case. If it has twin oil relief valves, it can be made up to any size engine, if it's single relief, only build up to 1641 max, The single port has smaller oil galeries

You will need longer cylinder studs to convert to 1,300 plus and drill the oil cooler to engine case holes out to fit the larger M8 studs on the twin port oil cooler

Oh!! another point is that VW did another 1 year special where the cases were bored out to adiiferent size where the cylinders fit in lol. So that might need checking.

Thanks all
Went to do some measuring yesterday (it'd in my Mother-in-law's garage) and didn't take my spanners or sockets! I'd popped the head and rocker cover back on loosely to keep everything together, but not loose enough to undue with my fingers only. 
Hey ho!

So the results are in.
Single relief valve.
Stroke 69mm
Bore I measured as 85mm
Cylinder collar outside I measured as 89mm

So 1641 already?

Bore on a 1600 is 85.5mm a 1641 is 87mm. So I guess you have 1,600