Having now aquired a manifold for my SUs, I now have two different size SUs. Not sure how to measue them, but wil work that out later.
The question is.....
Currently I have a 32/36 webber i think on a standard 1200 manifold.
Would twin SUs or the webber be more realibile and which can I set expect to be in tune the longest. I use this car as daily driver and want the eaisest option. I like the idea of SUs, but I have been told that they are very maintaince heavy and the webber is a set and forget thing.
Not so sure now what to do.
any clues??

The single downdraft would be most reliable and the SU's make more power but be a bit harder to keep in tune.

I'm kinda fond of the SU "type" carbs.
Just the ones made by Hitachi, mind you. These were stock on a number of Datsun models & i have had nothing but joy from mine.
The best way to use these is on their original GX manifold as a complete GX instalation. You will need an oval port head for that.
If you have a Webber, then use that first. If you like it, keep it, if not, go for the twin carb setup.

correct me if I am wrong, but deosnt the gx manifold require a gx head with the taller ports than the a14/15?

Quote:
The GX head shares the same port design & manifold stud pattern as all the later oval port heads, like A14 & A15 models.

Well i will keep a lookout for a gx head, but for the moment, I plan to use my ported standard head.
So I guess that the idea is that a webber is gonna be more user friendly than twin SUs, right?
If i decide that SUs are the go, the how muche xtra HP can I expect to get from the SUs compared to the webber?
basically would it be worth the extra misery of the constant tuning required with SUs?

I found some pics of SUs on the web and stuff, and i think that they are the 38mm units. They are the standard ones off a 1600, thats what the bloke said when i boughht them. Ita also helps that they came bolted to a 1600 manifold.
I also have a smaller type Su with the flat top domes. They would have to be about 20mm i guess. They came of a 1000 from my friends grandfather!
Another question would twin 38s be too much for a slightly more than street 1200.
( ported/polished head, 2mm shaved block, really lumpy cam, headers, 2"straight thru exhaust)

Hey rueby, have a look at this site:

http://www.teglerizer.com/sucarbs/

go through the tuning guides for the SU's on this links page and you will find that they are quite easy to tune once you have the basics. There is one link there that is specifically from Nissan and goes through everything to help you keep those SU's purring.

Hope it helps with the decision

No expert but,
Su's work on constant velocity. when u plant your foot down, u open the butterflies, but u do not raise the pistons inside the carbs. These pistons wait until there is more air entering the engine before they go up. In my opinion, it would be extremely hard to have su's which where to big.

with normal carbs, when u plant your foot, u increase the air passage way, and for a while, the air velocity enetering the engine slows down, this does not happen with su's.

Hey Rueby_Tueasdy

Are the carbs you have Hitachi or SU?

SU carbs bore sizes are not metric (mm) they r in inches ( inch & three quater or 2 inch etc...) Have you got 2 different sized carbs?