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Doing a bit of research this morning and I've found that the Midget Mk2 and AH Sprite Mk3 had marginally higher power outputs than the other 1098 engines as found in the ADO16 'performance' 1100's. Engine code was 10CC. I realise that that these were in-line units but what functionally differed from the ADO16 engines? Presumably the 10CC also ran twin HS2, a 12G295, so what was different to get a further 4HP out of it? Cam? Distributor curve? Or was it simply that the in-line engine was able to breathe better with an in-line exhaust manifold?

PS, there must have been some breathing difference as SUCarb's site lists a different Spring and Standard needle (Light Blue vs Red for the spring and An vs D3 for the needle)...

I’ve never worked much on North South A-series cars but my thinking is carburettors and exhaust system. I also think the transverse engines were affected and lost out with heavier flywheel and clutch assemblies

Alan

More googling.. I found an AKD sheet for the 10CC engine. I wonder if the primary difference is the compression ratio? The pistons that I have for my engine build are 8G2334/16 which are listed in this AKD as a low compression replacement at +10 thou for the 10CC engine. This in fact might be helpful for my engine build as there's only 18cc left in my 12G295!

http://www.spridgetguru.com/AKD3513/AKD3513MA1.pdf

gs.davies wrote: ↑Tue Dec 01, 2020 12:00 pm More googling.. I found an AKD sheet for the 10CC engine. I wonder if the primary difference is the compression ratio? The pistons that I have for my engine build are 8G2334/16 which are listed in this AKD as a low compression replacement at +10 thou for the 10CC engine. This in fact might be helpful for my engine build as there's only 18cc left in my 12G295!

http://www.spridgetguru.com/AKD3513/AKD3513MA1.pdf

I'm just building a 10CC engine presently and I was going to say when reading the opening posts, that this engine runs a higher compression ratio than any of the transverse engines that I know of.

I sourced a set of NOS BMC oversized pistons for this project, they are about, but very thin on the ground. They are not a bad design. There's some County Pistons I did find that had similar dish size, but the have split skirts and are of a 5 ring type, I was quite put off by them.

What’s the dish size of the pistons in your 10CC build and what CR does the a standard engine run at?

And I also understand that the cam is essentially an early Cooper S item..?

gs.davies wrote: ↑Tue Dec 01, 2020 6:07 pm What’s the dish size of the pistons in your 10CC build and what CR does the a standard engine run at?

The pistons have a 2.46 cc dish and the Static CR is quoted at 8.9:1.

gs.davies wrote: ↑Tue Dec 01, 2020 6:09 pm And I also understand that the cam is essentially an early Cooper S item..?

The Standard 1100, Sprite 1100, 998 Cooper, MKI Cooper S and standard 1275 engines all have the same grind of cams. The 1100 items for the most part had 3/8" lobes.

<Edited to add another Cam to the list >

Don’t know how much of a difference it could make but the Spridget inlet manifold is different to the mini one.

I had two customers with 1100 Specials both with original engines, one was A+ the other pre A+