Big SU's?

[tube80z]

For all the talk of Triple SU's, every setup I ahve seen on L-Engines have been failures. Mostly because they use 46mm Hitachi Stockers. Way too much flow capability for the suction piston to lift and fully uncover the jet and give full fuel. For proper sizing, you really need 38mm SU's like on the SSS setup. Now you take some Fairlady Z L20A SU's, and stick three of those babies on a 3.0L Engine, you should have proper flow capabilities and jetting out of the box, with the ability of easily supplying 150 rear wheel horsepower easily, if not 180...

 

Sorry I'm late to this party and I don't really intend to start a pissing match but this isn't really correct. My old 2.8 autox motor is now running a set of tripple SUs and I can tell you from driving the car it runs much better than it did when I had 2 high-flow SUs on the car (original Huffaker racing carbs). All these carbs were properly setup and in good condition, which is thanks to my friend Steve Epperly who owns ZTherapy.

 

I've also ran 2 46 SUs on a L20B and an L18 in a 510 and can tell you they provide better top end than the smaller 38s. You do lose a little low end. But back to the tripple 46 Z setup. This works much better than you might imagine. It provides more top end like a tripple weber or mikuni setup and a lot better low to mid-range. The only problem with all this is you need a manifold and a lot of custom linkage. I think the trick in making all this work is using the 2 litre roadster nozzles and needles.

 

With regards to the bored our rebello carbs I'd make sure to mount them so they are supported. When you bore a stock 46 MM body that large you'll find that only the outer ribs are holding it together. A few of these carbs have broken in wrecks. You'll also find that the larger 2 inch SUs have a much larger piston, which become the bottleneck when you start boring these carbs out.

 

Hope this helps,

 

Cary

[260pos]

I have a pair of HS8 SUs that were part of a Vintage Racing project plan that got cancelled. They are from a Rover 2000 TC. I'll sell the pair for $250 if one of you guys are interested.

I have a set of Rebello bored 50mm SU's that I'm not useing that I would sell for $500, they put out 280 HP on Rebello's dyno, on a pump gas stroker.

I would love to. It’s just that that rat b@$terd Santa pick pocketed me last month. I’ll make a note that you have a pair collecting dust though! Bah Humbug!

[260pos]

Sorry I'm late to this party…

…I had 2 high-flow SUs on the car (original Huffaker racing carbs). All these carbs were properly setup and in good condition' date=' which is thanks to my friend Steve Epperly who owns Ztherapy…[/color']

 

…With regards to the bored our rebello carbs I'd make sure to mount them so they are supported. When you bore a stock 46 MM body that large you'll find that only the outer ribs are holding it together. A few of these carbs have broken in wrecks. You'll also find that the larger 2 inch SUs have a much larger piston, which become the bottleneck when you start boring these carbs out.

 

Hope this helps,

 

Cary

 

Thanks for the reply Cary,

 

I ‘m looking for a stock-ish appearance, and I don’t have to recourses to make an intake manifold so I’m sticking with the dual carbs.

 

I don’t have the desire to snap my carburetors in half so the Rebello solution is out the window!

 

As far as the 2†SU’s go, couldn’t you run them without boring them out?

Or is the performance benefit not worth the effort?

Wouldn’t the larger piston be a benefit as it is in a larger bore to begin with?

Or is the L engine not able to create enough vacuum to lift the bigger, heavier piston? But then again the larger piston would have more area for the vacuum to lift multiplying its leverage.

When you say bottleneck, is it that the bigger piston couldn’t respond as quickly due to its mass?

Or is it that it would hang down into the bore?

 

Sorry for the barrage of questions,

 

-Jim

[Tony D]

Like I said in my post I have not seen a set yet that worked correctly---obviously, we have never met.

 

So that doesn't change my post's correctness. I don't see it as any sort of 'p-contest'...

 

But make no mistake, there is far more to changing jets and needles to make a triple 46mm setup work correctly. Springs on the suction domes come immediately to mind...

 

I never said they couldn't be made to work. Just that I hadn't seen one setup that correctly functioned yet. Maybe one day I'll see yours...

 

For the effort involved, though...C-B-A comes into my mind.

[tube80z]

As far as the 2†SU’s go, couldn’t you run them without boring them out?

Or is the performance benefit not worth the effort?

Wouldn’t the larger piston be a benefit as it is in a larger bore to begin with? ]

 

I don't think you'd need to bore the 2 inchers at all. That was in relation to boring a 46 and comparing it to a stock 2 incher. Figuring out needles and nozzles will be the next order of business when running the 2 inchers.

 

Cary

[tube80z]

But make no mistake, there is far more to changing jets and needles to make a triple 46mm setup work correctly. Springs on the suction domes come immediately to mind...

 

Actually all that was changed was the nozzles and needles to match a 2 litre roadster. I wouldn't have guessed it would have worked as well as it did if I hadn't seen the results.

 

I think part of the key is decent linkage and good carbs. I know that a lot of SUs are in prety bad shape. I get to see what people send into ZTherapy and some you wonder how they even managed to run at all.

 

Cary

[Tony D]

Yeh... Bad shape carbs is a poor starting point for any project. Many times people say this setup or that is "so much better than SU's" but fail to even consider their setup was far from optimal in the first place. Hell, even with good SU's people rarely take the time to tune them correctly for modifications to other parts of the engine. People say they are "simple carburettors" but have never retapered a needle or checked metering stations under load.... eeh! Never again. LOL

 

For the flow increase you get by removing the carburetted restriction and running a straight through 50mm bore, EFI conversion of the carb system makes for a tantalizing prospect. It's suprisingly easier than most think if you aren't a stickler for making something look "extremely stock" though with a bit of effort 'hiding' EFI in an SU setup only takes a bit of work.

 

I saved that photo of the Triple Setup, it looks like stuff I end up with... people walk by and don't give it a second glance because it's "another stock engine"...it's the one guy in 100 that walks by, then does a double take and says "niiiice!" is it's own reward!

[troyt]

Here is an example of a setup that works -

 

http://classifieds.hybridz.org/showproduct.php?product=3887&cat=17

[SHADY280]

i just got a set of su's for free, as far as i can tell they are from a 240z, and are really rough, prolly what you see at ztherapy. they appear to be round tops, but i dunno, im an injection guy. i actually got the whole motor for free, i saw e88 head and 240 rods, carbs and thought, hmmmm stroker?