Triple Carbs vs. SU

[ChrisA]

Chris, Just saying that the product out the door since Steve took over how the carbs are done has resulted in a better carb. Not that Scott necessarily built a bad carb the QC was up and down. If yours are working fine you musta got an UP set and that's good.

Steve, by the way, fixed all the Scott's "others" under warranty gratis for the duration of the warranty periods just so you all know where he is coming from customer care wise.

Thanks Bruce, I must have got an UP set then. So I'm not upset!

Just because something isn't perfect doesn't mean it won't work. Yes there is a firing order issue. But Jags, Austin Healeys and I think Triumphs all ran triple SU's on a 6 cylinder from the factory.

Yep, my brother-in-law's Healey runs like a scalded dog. Big 6 with triple's stock.

Chris A.

[e_racer1999]

that would be a great comparison.... GET TO IT!!!!

[hls30.com]

...

I for one would be interested in seeing a back to back comparison of dual to triple SUs to Mikunis or Webers. Especially if you were using Cary's old engine. That would really be applicable to my own situation. I expect that the Mikunis would come out on top, but I would be happily surprised if they didn't.

It looks like my car will be getting its stock L24 for Daytona-I have planned to rebuild and use my set of tripple 40 dcoe 18s for it. I have a local Dyno, and changing out a maniflold and linkage isn't that labor intensive...still a ways off though.

Will

[Mat M]

congratulations on a successful hijack!!!

I would be interested in a complete triple SU setup!! I would also like to know what kind of performance comparisons you would be able to test with your resources, as well as the outcomes!

[deadflo]

Besides the debate about how good the triple set up works with a inline six, what about how the triple Su setup would work with a stock engine? we have heard here before the triple set up doesn't add much without internal tweaking.

Although they would look totally cool.(They remind of me of early XKE's.)

[John Coffey]

I'm one of the skeptics based on some testing I saw years ago. Javier at JG Engine Dynamics built a triple SU manifold and put 6 EGT sensors in the exhaust header. On the dyno it was pretty obvious that cylinders 1, 2, 5, and 6 were running lean above 5,000 rpm compared to 3 and 4. Changing the needles on the first and third SU helped at high rpm but those cylinders ended up being rich under load at lower rpms. The issue appeared to be reversion in the intake manifold on those 4 cylinders and a strobe light shown on the first and third SUs actually showed pulses of the air/fuel mixture standing out of the carb throats until the engine went past about 5,000 rpm. Even then, the piston could be seen pulsing up and down with the strobe light on one and three while the piston on SU number two was rock steady.

Looking at the firing order and cylinder pairing shows why there would be reversion in the first and third SU.

Firing Order, Degree of Rotation

1 ----------- 0

5 ----------- 120

3 ----------- 240

6 ----------- 360

2 ----------- 480

4 ----------- 600

1 ----------- 720 (0)

5 ----------- 840 (120)

3 ----------- 960 (240)

6 ----------- 1080 (360)

2 ----------- 1200 (480)

4 ----------- 1320 (600)

1 ----------- 1440 (720)

3-4 Intake charge every 360deg

1-2 Intake charge 480 deg, then 240deg

5-6 Intake charge 240 deg, then 480deg

I'm not saying that this won't work and it probably will feel great on a street car. But if you're trying to extract the last bit of power you'll have some mixture issues to work through.

[tbird481]

Wow! Perfect timing for this thread...I'm in the middle of body restoration, motor rebuild was a couple years back and I've been looking for carb options. Running the original L24 with a Rebello E-31 head setup for ITS (and need to back off the cam for streetability), a set of MSA headers.

If there's a list for the triple-SU manifold, please add me!

Mark

HLS30-19137 1/71 Series1

[jmortensen]

Wow! Perfect timing for this thread...I'm in the middle of body restoration, motor rebuild was a couple years back and I've been looking for carb options. Running the original L24 with a Rebello E-31 head setup for ITS (and need to back off the cam for streetability), a set of MSA headers.

If there's a list for the triple-SU manifold, please add me!

You're running ITS and you were looking at a cam and now considering triple SU's? In the middle of a body restoration???

[tbird481]

Never ran ITS, was on a path to but changed my mind (and moved)...