from another forum strraight up GAVE me these in an effort to help me get my V12 running. i couldnt be more grateful.


Theyre XKE inlet manifolds complete with SU constant velocity round slide carburetors.







but ive already noticed a problem. one of the slides acts very different from the other 3. the first 3 have some resistance keeping them from sliding up and down. sort of like a rubber seal around a shaft.

the 4th slide has no resistance at all. ill post a video up later if no one has a clue what im talking about.

all in all, im totally stoked to see this project move forward. ill be looking into some fuel pump options shortly.

 

Damn, this one hellofagiftmyfriend! I suppose now you can get your motor to run at a reasonable power rate, so I do not have to wake up in the morning, thinking about whether your car is running yet

 

P.S. these are not flat slides, these have diaphragms and round throttle slides... I have the same two in my Mark2...

 

your right! my mistake. know anything about why the one round slide would slide up and down with no resistance(aside from gravity of course)? ruptured diaphragm perhaps?

also, 3.8 or 3.4?!?

 

I'd say some sort of internal issue, not sure if those have diaphragm in those, do not remember. My MK2 is 3.8, plus the donor one is also, 3.8, so I have 7.6 all together.

 

seems like some sort of air equallibrium is causing resistance in the other 3 slides. this one has nothing.

 

Just in case this is useful, the SU carb works like this.

There is a diaphram with the jet in it underneath. This is accessed by unscrewing the bottom casting. there is a spring underneath the jet diaphram that holds it up against the adjuster. Check on all four that the jet and spring assembly is OK

On top, the "bell" shaped bit has a slide in it that is damped by a plunger that fits in an oil-filled column. If you unscrew the round plastic knurled top (about 0.5 inch wide) you can withdraw the plunger and top up the damper oil.

The slide itself holds the jet needle (as the needle rises with the slide, the tapered needle effectively increases the jet size). If you unscrew the "bell" top of the carb the slide comes out and the jet needle can be accessed and changed. Check that the slide is not fouling the bell at all, if it is polish out any highspots.

One reason for one slide moving more freely that the others would be that the damper oil needs refilling.

Greg

 

Can't wait to see them installed! And better yet, pics with you in the car on the road! Congrats on a great parts find

 

i would wager a guess that your right on the money with that one! is the damper oil anything special? google says a 20wt non detergent oil will work (fork oil, motor oil, etc)?

Thanks!
there was a mint set with strombergs on ebay for $3,000 (thats no typo)

one guy offered to sell me these for $500 + freight.





a week later, another guy had a set for $200 + freight but they were somewhere in the atlantic on a shipping container and wouldnt touch down for weeks, and then this guy offered me the SU's and intakes for freight + beer money. too bad UPS wanted a God awful amount to ship them.

This guy really helped me out BIG time.

 

SUs are much better than Strombergs, I think, and simpler. Any oil will do it, about 20/30 as you suggest.

I have no idea how an HE will run on them though, or the correct needles/jets to use. Different needles to adjust the mixture (outside the jet adjustment range, that is) are easily obtainable though. The jet adjustment works by changing the 'starting' position of the tapered needle in the jet, thus permanently starting at a leaner (smaller gap) or richer (larger gap) position.

Burlen Fuel Systems is the SU specialist: Burlen - Burlen Fuel Systems Ltd
and they can supply everything you may need to rebuild them (eg jets, needles, spindle seals, gaskets etc etc).

Greg

 

well it cant run any worse.

thanks for the links.

 

Follow Greg's advice, sounds to be right on the money.

With SU's or Strombergs, I always topped the dash pots with my weekly engine oil check and added whatever engine oil I was using. Very common carbs on Brit cars + old V8 Rover engines.

PS, don't think about doing a spot of internal cleaning with a high pressure air line you can quite easily shatter the very brittle floats. Ask me how I know.

I'd get hold of a maintenance kit and do a spot or R&R, new diaphragms etc even a pin hole can have a massive effect.

 

SU's are a black art to setup. It's forty odd years since I used to do it.
There are two phases, one is getting the throttle opening on each carb the same, you do this by removing the air filters and listening to the intake hiss with a stethoscope ot a bit of tubing. They must all sound exactly the same.
When they do you tighten up the linkages and listen again.
Then there's getting the mixture right which is covered here Set up and balance twin SU carburettors
If they came off the same engine as yours the needles and jets will be OK, if not you will have fun. Good luck and, above all, avoid lean mixtures.

 

they came off of a flathead V12. no idea what issues that will bring me.

 

As I recall the jets have a number stamped on them you can see by removing the 'top' of the carb, the needles are engraved, you have to remove one to see.
If you get in touch with SU Contact Us | SU - The SU Carburetter Company they'll tell you the right combination for your car - unless a forum member can come up with the info.
You must get the correct ones for your engine or you'll be in a world of misery.
BTW looking at these I think they're the earlier non-diaphragm type. Pull the top off one + post a pic please.

 

I thought you fixed the leaky manifold to ECU vac hose, and were running now????

I think the SU's will work fine at idle, and wide open, but I think it will always be too rich at part throttle cruise on the HE.

Dave

 

When synchronizing these, a stethoscope works lovely as Steveinfrance mentions... but in a pinch, a plastic soda straw can work if you want to get your head close to the engine. The soda straw "whistles" with a pitch making it easy to tell what the intake level is on each carb. A more sophisticated way to do it is a "sync-gauge" like the use on 4 carb bikes. Here is a link for one on Ebay - Vacuum Carburetor Synchronizer carb sync Gauge Honda GS CB KZ 550 650 750 850 | eBay. I am guessing these folks who have these carbs for sale either are parting out their cars - sad - or installing webers, which is a very groovy thing! (a weber setup rocks!). Best of luck on this endeavor. Brings back fun (yet tedious) memories!

 

I can't say seeing the back of a succession of multiple SU's was the saddest moment of my life. Thank Gawd for fuel injection.
If they're the early piston type there's even more fun - you have to centre the jet on the needle otherwise they will stick open. 40 years and the pain is still there !!

 

You can also get parts for them in the states here Apple Hydraulics

You are going to need to change jets. also you will need to use a manometer to synchronize the carbs. Jetting is no different than any other carb. Read the plugs and adjust until the plugs look right and it runs how you think it should.

Ultimately you will spend more time and most likely money getting these right than you would have fixing your mess of an EFI system. However I know you will never admit or let us know the truth on that one. Good luck!

 

the problem with troubleshooting an EFI system that runs differently everyday is.... well its just that. it runs differently everyday. it was a 4-6hr a day project for 3 months and im sick of it.

Megasquirt will come later, but for now this will do. it wont be a hotrod, but maybe ill get to drive it before winter comes back again.