12a, dual SU carbs
 

I've never seen these until now, they look pretty nice to me. I'm looking to buy a pair of these carbs, with intake manifold for my 12a. Previous owner pulled them off a streetport 12a he found in a junkyard. He says the size is 1.75'' each, which means nothing to me. What size in other carbs is it comparable to, dellorto 32 or 36??? How much do you think these are worth?

one pic of them mounted is here: http://www.hurleyrotary.com/images/1...Conversion.jpg

Once the forum stops being gay I'll try to post some better pics that I have on my comp.

tuning dual carbs? you're brave :)

actually the triple carbs on the old 240Z were a bitch, but looked oh so cool :drool:

Mmmm, tri-Webers...:drool:

One of the local AutoXers here in Skoon has a '69 240Z with the tri-webers. That car hauls ass. Very nice setup indeed.

note sure what they are comparable to but they flow a lot of air ... you tune them by changing the tapered profile of the needles, I'm sure Hurley can hook you up with the correct bits

I have some good pics of these carbs, but the forum won't let me upload them now for some reason :(

SU's were used on British cars from the 1920's through the 1970's. They're actually very easy to tune, (I have a 1971 MG Midget) IF they are in good shape. What usually happens is that after many years of use, the throttle shaft wears out along with the bushings the shaft rides in, and air gets sucked in at the shaft. They can be easily repaired to as-new condition by an expert. Two carbs would cost about $300 to rebuild as-new. That would include EVERYTHING - throttle shafts, bushings, jets, needles, floats, etc. The best SU guy around is Joe Curto. He works out of New York, and does business by mail. You can find his ad in Hemmings, in the British cars section. My MG has a 1275cc engine, and uses 1.25" SU's. 1.75" seems a bit large for 12A. (1200cc)

SU's are great simple carbs. I'd say GO FOR IT.

I got a nice Grassroots Motorsports article on SU's I can scan and send to you if you buy them.

Seeing that 1.00" is 25mm, 1.75" is 43.75mm.

Seeing that most aftermarket carbs for 12a's are 44mm to 48mm, I'd say a 1.75" SU is a little small. If your motor is ported I'd reccomend 2.00" SU

later,
-bp-

su carbs
 

i have a 73 triumph tr6 with 2 su carbs / they are 1.75s. the motor is 2500cc. i think two would work on a 12a.
they are very easy to rebuild and all parts are available.
1.75 is inches / there are 24.5 mm in one inch (i think).
you do the math. the jet that the needle slides in will were out and make them run too rich. hope this is some help

Yea.. these carbs are stupid simple to tune and rebuild.. I can rebuild these and Zenith-Strombergs (also used on a lot of 70's Brit iron) in my sleep. Nikki's aren't too complex, but SU's make one look like a 6000 piece jigsaw puzzle. And don't let anyone try to kid you and tell you horror stories about tuning them. Pick up a Uni-Syn (like $25 last time I checked), a Haynes manual for SU/Stromberg carbs and have at it. The problems people have are from those who have no clue how to tweak these carbs and just start screwing around with stuff. With constant depression carbs like these, going a size bigger than you need won't hurt like a normal 4-barrel, as the carb will only allow enough fuel out to satisfy the vacuum the engine is making. I'd say go with the 2" SU's as well, but you may have some trouble finding them. If I recall correctly, they were limited to Jags and the 6-cylinder big Healeys. Grab yer ankles if ya find a set.. :D

--Danny

It's TWO 1.75'' carbs :)

Also, what fuel pump & reg would you reccomend for running dual 1.75'' carbs. I have a stockport engine, with stock manifold, gutted cats, straight pipe to a 2.5'' straight thru stainless muffler. I will also be getting an RB header and presilencer to complete my exhaust setup soon.

pic1

Still won't let me upload anything :( I've got 6 good pics of them too...

email me the pics and Ill host em... webmaster@frontfly.com

pic1
https://www.rx7club.com/forum/attach...postid=1498930

pic2

:( I got one up, still doesnt want me to upload though.

Those are the nice ones. Some SU's had a sliding "plunger" like those do which varies airflow. The cool thing about the ones you have there is that at full throttle there is nothing blockling the airflow. Some of the other SU's used the typical butterfly setup. I'd love to get my hands on a set of those.

I think these might have that butterfly you're talking about. I have 5 more good pics of them, the forum just wont let me upload them :(

http://coldy13.tripod.com/pic2.jpg
http://coldy13.tripod.com/pic3.jpg
http://coldy13.tripod.com/pic4.jpg
http://coldy13.tripod.com/pic5.jpg
http://coldy13.tripod.com/pic6.jpg

and if the pics dont show up for you, there are here:
http://coldy13.tripod.com/pic1.jpg
http://coldy13.tripod.com/pic2.jpg
http://coldy13.tripod.com/pic3.jpg
http://coldy13.tripod.com/pic4.jpg
http://coldy13.tripod.com/pic5.jpg
http://coldy13.tripod.com/pic6.jpg

Sorry for being a post-whore, but you have to copy and paste the url's, tripod is gay.

ALL SU's had the sliding needle setup with a butterfly after it.. these carbs are similar in design to motorcylce carbs, and they can require as much or more air than our engines do at full song. You don't see them choked for air do you? The pose very little threat in restriction of airflow... The only thing that varied with them was the float bowl setup, the needle and jet size, diameter of the intake and the bolt pattern on the back of the carb..

--Danny

Really? I saw a couple taken apart. Didn't know that. Good info. Its not like they are restrictive anyways.

I had 2 SUs on my 59 Sprite and they worked like a charm. Easy to tune and reliable.

That direct sidedraft hookup looks really good.

B

su carbs are good for a stock car, but for hi performance they suck!!!!! i had them on my 64 vovo!!!!! 1/" 3/4

and on my dads 59 austin healy bugeye, 1"


the webers are much better!