su sidedraft carbs for a banger

i will be building a model a truck and i will be building a very mild mercruiser 140hp chevy 4 cylinder engine for it. i would like to run 2 su carburators on it . the engine is 181 ci .do anyone know what dual su carbset up would be good to used on this engine. i was looking at a factory set on from a british car but it get very confusing not knowing about british cars . also are su carbs very tricky to rebuild ? are they reliable? thanks for any info you can provide

 

S.U. carbs are very reliable and simple to tune. I have a pair of HS-6's on my race TR3.
You will have to fab a manifold as they are four bolt side draft carbs. The cool thing is they are a variable venturi carb and are efficient.

 

do it,do it .those carbs will will work magic with that engine,and look awesome .there really is'nt much to them as far as rebuilding them

 

Just remember to keep the slides lubed with silicone spray NOT WD-40.

 

Here is a handy chart on SU carb sizes for your engine.


The web site I hawked it from

http://www.sw-em.com/SU_vs_disp.jpg

Looks like your app would call for a pair of 1 3/4" instruments.

 

I have been running 2 bolt SUs on my Model A 4 cylinder for several years. SUs are the best carburetor ever made
The 4 bolt SUs may be too rich

 

god reliable and you tune them with a screwdriver
you can fine tune with jets and needle but
you dont have to in most cases 2 h6 or hif 6
are what you need on that engine, Hif are
better since they got integrated fuel bowl
one less chance for fuel leak
you found them on many volvo 140, 240
on 240 they are single but you can take
2 single and fab up some linkage
i have run them on many engines and they
work grate
if you want to go bigger there is the H8 that
is 2 inch hif 6 is 1 3/4"
And you dont overcarb with a su it takes
the air it needs and nothing moore

and dont listen to tips about use atf-saltwater
brakefluid-wd40-and other magical solutions in
them

 

"and dont listen to tips about use atf-saltwater
brakefluid-wd40-and other magical solutions in
them"

They need a thimble of oil in the dash pot on top, nothing else.

 

thanks everyone for the info. i can fab the intake no problem i just need to get some carbs now.

 

I picked up a set of SUs from an MGB that have the remote bowls, I intend to set them up on my A banger. In the past I put 3 on an inline 6 in a little timber ski boat and they worked great.
Brendan

 

Here is a picture I found that I have been keeping of a SU set up on a banger.
Hopefully I am not offending someone by showing it.
Brendan

 

This is kind of a funny post because we just pulled a set of SU carbs off an old Austin Healy road racer to put on a single aluminum intake and Weber carb. This was done mainly because it is a pain in the rump to tune this thing. If it was driven constantly, it would probably not be that bad, but when it is started and driven infrequently, every awakening was a pain in the butt.

And no, the originals are not for sale. This car has been in the family for over 40 years so the original parts will stay with the car.

Good luck on your project. There are some great Austin forums out there with a LOT of info on these carbs...

 

Check out this thread;

http://www.jalopyjournal.com/forum/showthread.php?t=443369&highlight=su+carbs

I sourced the HS6 carbs over here in the UK for HAMBer 6inrow.

You have 2 choices on the carbs - go for the older style with the separate float chamber (looks vintage) or the newer HIF series. They were fitted to many, many British cars in the 70's and 80's. Haynes do an excellent manual and there several good tuning manuals.

The HIFs still look pretty much vintage, can have the dashpot polished up and have a number of useful improvements.

Of course, virtually all types of SU can still be bought new from Burlens Fuel Systems and they sell everything you would ever need.

http://www.sucarb.co.uk/

HIF's suitable for a rebuild can be picked up here for around $30 USD and rebuilt for about the same.

Almost any engine will run sweeter and get better mileage on SU's - it probably won't make better horsepower but probably won't make much less. I see it as a good trade off.

Remember it is a side draft carb but I've converted cars to run on SU's with their original downdraft manifold by simply making up a couple of adapter flanges and welding them to a 90 degree pipe bend.

Because of the design of the SU, virtually any engine will idle smoothly on any SU fitted with any needle. The trick is getting it to work right through the rev range without flat spots and "bogging". This is done by choosing a needle with the right profile over its length and, to a lesser extent, by the strength of the spring in the dashpot (and to an even lesser extent by the viscosity of the oil in the dashpot). There are computer programmes to help you find the right needle from the hundreds available off the shelf, but you can also make your own profiles using a fairly simple process.

There is a straight-forward routine for tuning an SU to a engine iit was never fitted to as original equipment.

I fitted a big 44 SU to the Citroen 2CV (602cc) flat twin engine in my trike - normally this would be WAY over carburrated but I put a divider into the intake manifold plenum and effectively made a twin choke 22 SU. Very forgiving carb and much under-rated.

I'd like to convert my 347 Pontiac to run on a pair of 2" SUs or maybe 4 x 44 or 38 HIFs.

You could run your inline 6 on 3 x 38HIFs or 2 or 3 44HIFs (depending on the needle size you choose). If you have any trouble sourcing carbs or spares over there let me know and I can help out.

 

i am in the hunting stage to find out what i need and where i can get some .

 

You arent offending me. I'm flattered that you like my work enough to keep my picture. I just got another engine rebabbitted and counterweighted so that rusty engine is coming out and the stainless manifold and the SUs will still be in use. I made air filters to fit after that picture was taken.
I've been running a SU on my 1946 Harley since the 1970s.

 

There were also a lot of Volvo's built with dual SU sidedrafts on them. You can usually buy a matched set on that big auction site for reasonable money.

Edit: I just took a quick look on that site, there's a pair of HS6's currently sitting at $26, five days left. Do a search on volvo su carburetor

 

now i do have a question. if i use these carbs i woul like minimal modifications to them. i can make the manifold and linkage no problem but i am not a carburator expert. the volvo is 1.8L and the 181ci mercruiser is 3.0L. will this work ok with out much mods? i would like to find the best su's that were off of an engine about the same size or that will work right with out alot of work. any thoughts??????

 

ok so i reread the posts . looks like i need two 1 3/4 us carbs. thanks again guys. now to track down some carbs.

 

OK all this discussion has got me motivated,
I have just ordered a flange from hellsgate to start working my headers and manifold for my SUs.
Brendan

 

I would look more for an engine with matching horsepower than matching displacement. In other words, a 1930 flathead would likely require smaller carbs than a 1990 OHC engine of the same displacement.

The carbs off an 1800 cc Volvo would probably be fine. At worst you would suffer a small loss of top end power, cutting your top speed to 105 MPH from 110.

 

A single 2'' SU will flow more than a pair OF 1 3/4'" carbs and you will not have the linkage or synch issues that seem to bedevil those not familiar with multiple carbs.
It is possible to have a downdraft SU that could bolt to your existing manifold - IF the hole in the manifold is at least 2" in diameter.
However if you are want the multiple carb look go with twin 1 3/4.
No carburettor gives a better milage and power combination.

 

One note when designing the manifold for your carbs. The fuel bowls should be mounted upright so pay attention to the carbs you get. The angle between the fuel bowls to the bore will determine the angle you want to tilt the carburetors.

 

NMCarNut,

Can you adjust the angle of the bowl on an SU?

 

I am not aware of any SU that has an adjustable angle, although depending on the application there are different fixed angles.
However, since there is only one simple fuel passage from the bowl to the main jet if you are or you have an ace welder friend you can wack, rotate, and reweld the bowl to the mount. The critical part is you want to be sure that the vertical dimension from any fixed point on the bowl to the main jet remains the same.
Attached are a few pics of a spare carb from a Corvair Spyder project from about 30 years ago. The similar carb that was used worked extremely well.

 

Mine look like they're for a later application- will try to get some pics over the next couple of days to compare!

 

The ones on my 60 Austin Sprite have a span of adjustment.

 

Except for the Fish. Here is a Reece Fish built under license by the late Leonard Reece in England. It has a bowl that swivels so you can run either as a downdraft or a sidedraft. This design feature is specific to the Reese Fish - not the U.S built Fish or the licensed Minnow Fish built in Scotland. This is a direct bolt on replacement for SUs and gives better performance and fuel consumption. I ran one on a Mini 1275GT single carb 53 bhp engine and it woke the thing up which then performed like a Cooper S with 71 bhp.

I am planning to use the Reece Fish carbs on my Daimler hemi to replace the opposed factory SU setup. But the SU can look really bitchin when polished and with a decent air cleaner. They have a wonderful organic vintage look and feel to them....

 

Weasel,

Thanks for sharing, and saw your other post about your Fish carb find- would love to find a pair for my Chevy 4 someday.

 

and just a warning, some of the brits went to a single zienith stromburg, they look like a fat SU they suck! lol stick to SU's

 

well thanks to a fellow hamber i will be gitting a set of su carbs for my banger. he just asked me to pay for shipping . big thx man. now i can mock them up and see what i have to do to get them to work by fabricating a manifold.