Inliners International Forums General Discussion Hi Performance SU Sidedrafts

I've got a chance to get a great deal on a bunch (6) SU carbs from Triumph TR6 engines (2L.. 121 CU)

Anyone ever run SU sidedrafts on their Chevy inlines? What experience did you have?

I realize that my 500CFM Edelbrock is probably a better carb and much less hassle factor but for the art deco 'look' of my roadster, the SU's would be perfect..

su carbs are real popular in OZ with the hot up people-a really great carb.if using triples ,they will out perform any 4 bbl(especially 2" ones)make sure you get the butterfies bushed and balance the carbs and you'll not look back(good on the fuel too-if you don't drive silly!)nostalga racers are still using SU's as they even out accelerate webers

I've never used SU carbs on a Chevy inline but I think it's a good idea to try it especially since it'll look "period correct" on your stylish roadster. During my sport car racing days everyone used to shorten and stretch the dashpot springs,add ATF fluid for even response,the ATF seemed to be more stable,and play around with the needles.I would leave them stock until you gauge how they work and I would also invest in a UNISYN carb device(available at Summit Racing) for balancing them. Are you fabbing your own intake manifold?

sounds like a cool idea

Sounds like a dumb idea. So, will you have three of those left over?

I have a unisync left over from the Triumph 2 Liter I owned back in the late 60's. I remember trying all sorts of things with them but I've slept since then....

Yeah, I'll fab my own manifold. It'd be nice to run progressive linkages and just use the center one for idle.

If I get all 6, I'll probably end up with 3 good ones from the batch.

I don't get it. Why is it a dumb idea?

Unisync have there place, but I was never real happy with the results. When I was rallying a Volvo I used a kit that I got from the local FAP dealer. The kit consisted of two aluminum tubes and wires. The tubes slipped into the dampers were you filled them with ATF and the wire slipped into the top of the tubes. You backed off your adjustments then lined up the wires so they were even. This gave you a mechanical reference as to how far the dampers were open. As you adjusted the carbs the wires were kept even. Simple, no guessing if the indicator was the same place from one carb to the other. The kit also left your hands free to adjust the carb. I think I still have the kit in one of my tool boxes, if someone is interested. You could probably make set your self.

Larry

Larry, I'd be interested in building a set or whatever. I lost the auction but got the second set on a 'second chance offer'. Hopefully these will all be rebuildable.

I just did a google out of curiosity and found a link with a copy of the instructions. In addition the same company STE, West Germany makes the Unisyn and they say for precision you want the Unisyn. Here's the link to the instructions;

http://www.mgaroadster.co.uk/SU%20Carburetor%20Tool.pdf

Kerry I sent you a PM.

Larry

Webers are very old carbs & would look good also for a vintage look.
Two cents
MBHD

Absolutely would Hank...only trouble with Webers is the PRICE! Out of my budget for sure.

(joking???)cause he wants them???

I want it all! Actually I think that would be a really nice set up. Sorta' different and traditional at the same time. Plus it would work well. Keep us up dated if you pull it off!

hERS A COUPLE i'M USING ON MY '30S ERA CHAMP CAR WITH A 300 CROSSFLOW. i USE THEM BECAUSE THEY LOOK "OLD. tHERE IS A GOOD 2 HOUR VIDEO ABOUT HOW TO REBUILD / TUNE THESE. i'LL GET YOU THE ADDRESS.

Sorry about caps lock.

They came in. Stromberg 175 CD-2's Rebuild kits about 30 bucks each. They look good and are complete. I'd be interested in that link Frenchtown.

I'm wondering if I can build a 'log' type manifold and have progressive linkage. The center carb would do the low RPM stuff and the other two come in later. I know the stock intake manifold worked off a single 1 bbl but my engine isn't stock. Flat top aluminum pistons, big valves, lump port, 500 lift cam.

Also wondering about runner length. I've got room to make them at least 12" long. Seems like the longer runners give more torque if I remember correctly????

Thoughts?

Hmmm... The SUs are a constant velocity design, meaning the air valve opens only enough to maintain velocity through the ventuuri so I don't see the need for progressive linkage with several of these carbs. I don't think fuel economy would be better and you might get into an unstable / bog condition with progressive linkage used for agressive driving. Dunno. I would just hook them up all direct.

Likewise, a friend of mine tried a plenum on DCOE Webers with no improvement. I think a more conventional manifold is in order, with minimal plenum volume. Just my opinion - no real data.

Kerry,
Here is the info on the "how to" tape:

Titled "Just SU - The definitive guide to the best British and Japanese carbs ever"

Http://www.ztherapy.com for pix/tech c 2001

Can you tell us where you got your rebuild kits? $30 seems pretty reasonable. Did they come with new hoses for the enrichment needle? I understand those hoses can be problematic if cheaper alternatives are tried. Any insight / advice for us?

Actually Autozone has the GP Sorensen kit for $21.00 Stromberg 175 CD-2 ...no photo though. We have a new Advance Auto parts nearby and the others are in town 10 miles away. However for a total of 30 bucks for the set of 3, I'll drive into town.

76 TR6 However, the stock engine had only 2 carbs and I got three...so I'm not sure what it came from. Only one of the carbs has the lower replacable jet. The rest have a plastic plug with Oring. There are several sub designations of the CD-2 series. Don't have a clue which one to use.

Here is a photo for a similar kit.


What do you mean by 'minumum plenum volume'? Same cross section as the bore of the carb?... 175MM??

I'll call the ZT folks monday and see if the ZT carbs are similar to the 175 CD-2 to make it worthwhile.

Hi Guys, it's been a while since I posted. I've been working on the roadster body.

A friend has build a foundry and we're going to try and cast a manifold. The plan is to have three identical cast tubes with the appropriate flanges. I'll fab a plate to tie all three tubes together at the carbs but they will all be independent and feed a single port. Yeah, tuning will be a bear but that's the plan for phase 1.

OK, a question. When I started this thread earlier this year, I titled it SU sidedrafts but my carbs are actually Stromgbergs. I know they are very similar in operation but are there significant differences/advantages. Back in the early 70's I owned some 6 cylinder Triumphs with Strombergs. At some point, apparently Zenith took over Stromberg??

Finally, I learned something last night. When I first researched the carb kits I found them at Autozone. My eldest son is now a store manager for Advance and I asked him if they could cross Autozone part numbers. They can and I've ordered

Item: 96-305
Notes: Zenith model O.E.M. #175CD-2S, 175CD-2SE

Each kit is about 18 bucks. I ordered only 1 to see what was actually in the kit and make sure it is the right one for my carbs.

Thoughts and comments?

Take a look at Jaguar XKE's and others, they are very simple carbs! you have essentially ONE variable and that's the needle. You can modify them or even make new ones if you have a laythe they were used in EVERYTHING from the Aston Martins to the Rolls Royce's AND are known for getting great milage. HP, I think has a book all about SU's.
True, Webers are the untimate but they also have about 40 variables each!, and the mysterious EMULSHION TUBES that follow no logical pattern.
Su's come in various sizes and (3) 1-3/4"s ill be great for your car
cheers;
Roar

Guys, I run a pair of SUs on my Ford six. I made my own manifold and it works very well. The following link should take you to a slide show to see it.
http://s737.photobucket.com/albums/xx14/bigbill-photos/?albumview=slideshow

What is the difference in SUs and Strombergs? They appear to be very similar designs.

SUs have a piston that runs up and down in that cylinder above the barrel, that opens and closes the throat when vacuum from the section between the butterfly and the piston varies...

Strombergs operate using a diaphragm, but it's still functioning the same way.

I believe, however, that the strombergs don't have the needle type of operation that the SUs do. I don't have one here to look at so I can't confirm it, but I seem to remember reading somewhere that they have a screw adjuster in the base.

I'm sure you'll find diagrams and more online. The Strombergs are called 'CD' types.

Oh yeah, both are very good for economical driving in most circumstances...