I have a AH 100 BN2. What size are the original carb sizes ??
Can I upgrade to 1.75 as a M option
Was the 100S with what size of carbs.
Thanks

Original size is 1.5", yes you can upgrade to 1.75" but will also need the correct size manifold. Do not know the size for 100s

I believe the 100s was 1.75" SU as well, the 100s has a totally different crossflow head if I recall correctly.

Greg

most 100S got H6 carbs, I think some may have been fitted with 2" H8 carbies.

Hello glemon,

Just to let you know the regular 100/S didn't have a crossflow cylinder head. It had the 4 inlet and 4 exhaust ports on the opposite side of the head to the regular 100.

Best regards,

bundyrum.

Thanks, I knew it was different, couldn't remember exactly how though, I have a pic from when I saw a couple at Healeywerks a couple years ago, bad memory.

Regards, Greg

BUNDYRUM,
Even if you got a 100s head I dont think its a straight swap out from memory, or is it?

Hello again zblu, your right it's not a straight swap.

The head stud position is different.

The distributor is in the way and has to be moved to the regular 100 tach drive position.

I haven't gone into it completely at present but when I get to do my BN1 with the 100/S head I'm sure to find out.

The conversion has been done in OZ a couple of times that I know of.

Best regards,

bundyrum.

Hi, my 100-4 came with std carbs, 1.5" I upgraded to 1.75"'s as I bought a very bad rotted out M spec converted car. It was a late 1953 bn-1 car.
http://www.youtube.com/results?search_query=austin+Healey+100&search_type=&aq=f
You can see the set-up on You Tube.

If you want to convert, the easiest way is to get a set from a TR3 OR 4 using parts from your 1.5" carbs, the bowls, copper cross tube and other fittings you can almost get them to look like the original M spec set-up available in the 50's. The manifolds are available at DW. I tried M spec needles and ended up using the TR3 std needles and M spec dashpot springs.

Johnb