I am interested in any advice on puting SU's onto either an inline 6 GMC (228 for now) or a 'Cadillac 261'. In my best estimation I should go with carbs that have a throttle bore roughly the same as the port at the intake flange. So I am leaning toward H4's or a variant therof.

The only reason I am considering SU's over Mikunis or some other 'motorcycle' carb is for appearnce.

I have searched for this, (even asked in a PM, thanks Mr. M ) but I am hoping someone has actually done it. If you think it's a dumb idea, I want to know that too, please share with me (and everyone else) why you think so.

aussie's have used SU carbs since the year dot on all our inline 6's-great carbs and pretty good on the fuel.top acceration too(all the nostalga inline drag cars that run carbs tend to run su's).on a 261 cu in go for three 2" carbs off a jag 6(4.2 litre)jetting and needles should be ok from this motor too.

I had SU's ,but only on import motors.What I did like was that you could get them wide open very quickly with little modification. I used to change the internal throttle spring and play around with different needles and bores. I always used trans fluid for lube,although today there are probably even more and better ways to modify these.

Hi!

Nexxussian

My fathers car is a Chevy 261 L-6 engine powered that uses a triple SU HS4 (1 1/2") carbs with tube sheetmetal intake. If you want some pics, just ask. It uses Isky cam, split tube headers, flat top pistons and about 8.5-9:1 compression ratio. Makes 162 hp and about 33 mkgf of torque. It uses DJ needles. We bought the new needles from Burlen and also bought the nice book called How to Build and Modify Su Carburettors for High Performance (The SU Carburettor High-performance Manual, from Speedpro series).
I can take some pictures of the intake if you want. Feel free to ask anything about it.

P.s.: it's a brazilian 1967 car called Uirapuru and it came stock with SUs. I sent some pics to Hoyt already but can send it to you too. It's the first brazilian made sport car to pass 200km/h (about 125 mph). Nice and fast car.

Based on quite a bit of experience with SU's, albeit a long time ago; depending on cylinder head configuration and intake manifold configuration, I believe you could make either (3) H-6's or (6) H-4's work successfully.

Tuning triple SU's is not overly difficult, assuming you have lots of experience; however, it can be quite challanging if you have no experience in tuning SU's.

Tuning (6) SU's is challanging.

Give me a call during normal telephone hours, if you wish to discuss.

Jon.

Dear Jon;

Do you have any experience or specifications on the SOLEX carbs??

Thanks.

Much, much more than I wished I had! And, with no offense, I have no desire to add to my experience!

Jon.

We know Inliners are not to post there own businesses in these forums, but just as I reccomend t6 racing,I'll reccomend carbking's in case some members are unaware of his knowledge and services.
www.thecarburetorshop.com

Thank you Drew.

Jon.

i,am considering useing 2 or 4 S&S harley carbs on my 181 chevy 4 cyl. engine

Thank you all, I wasn't expecting this much so soon. I haven't any experience with SU's Just Mikuni CD carbs (and other non CD carbs). I think the SU's would look better in my aplications though (both are going for a more vintage look at this point). Both have 3 intake ports for 6 cylinders (unless I win the lottery and come up w/ a 12 port ).

Look over in the Racing section at Ray Hedstroms '41 coupe "Inline Fever" We set a record at Bonneville useing 3 S&S Harley carbs. Al Cunningham out in Texas, used three on his car as well. They are easy to tune and get parts for. Second best thing to fuel injection.

Thanks, Armond.

I had a Volvo P1800 for a few years that had a pair HS4 SUs. Yes they were easy to tune. I forget the name of all the parts. The trick was to get a tool from your local foreign auto parts. The tool was a pair of pipes that replaced the diaphragm damper with wires were place in the top of the at a right angle. Back off all your adjustments and line the wires up. Start the engine and tune while keeping the wires lined up. Could never find a set of needles I liked to go with the Isky cam.

Larry

Drew, or some of the other guys who have been to the Latimore, PA Inliners meets, may remember an Inliner from Maryland with 3 SUs on a '53, or '54 Chevy. They looked good and the car ran and started nicely. For the life of me, I can't think of the guy's name. I do remember that he liked them and got good mileage with them, too. If you could contact him, I'm sure he'd be glad to help with info.

Well, Mark Super is from Maryland, but I don't remember if he had SU's on his Suburban. Searching my pics,I couldn't come up with an engine pic with SUs. sorry.

Thank you Mr Griffin, Dennis and Drew.

I have read about the wires, If I understand them correctly, they are an indicator of where the piston in the carb is positioned while running.

Correct on the wires.

Larry

Tom Langdon @ stovebolt ran three SU's on his 39, he would be a good one to talk with.

Does anybody has the software to help choosing the best needles for you specific aplication?
I don't believe it solves your problem but it can be a baseline for the tuning.
Burlen Fuel Systems announcesomething like that.
Thanks.

Mr. Griffin, Armond and Mr Chevy 250&261 Thank you.

I will have to get in touch with Mr Langdon.

Great minds think alike! I had similar plans, but with the 40mm Harley Keihin CV carbs. One feeds an 88 cubic inch Harley just dandy, so 2 should be about right on a 181. They're fairly cheap too, as the Harley performance guys don't think to highly of them.

Bob

Anyone have any pictures of the Harley / Keihin CV carbs? I know what the Mikuni equivalent (ok, they're 36MM but should 'look' about the same)?

I have two in the basement for a similar project. Do a search on ebay for them, many pictures will come up.

Armond, you mean Tom Langdon of the Stovebolt Engine Company don't you. I have been turning the stovebolt.com site upside down, DUH. I guess I must have figured you meant he was on there. Oh well, I'll call him in the morning.

Nexxussian - one issue to consider with SU's is the lack of accelerator pumps.

SU's were used primarily on engines with very little torque but high RPM. Performance in the lower RPM range's is marginal. Do a little research on the gear ratios utilized by the imports to allow the engine to obtain RPM quickly when torque was needed. Standard transmissions were also primarily used.

The lack of accelerator pumps does contribute to better fuel economy.

Some of the more expensive O.E. installations (i.e. Jaguar) incorporated an auxilliary electric "starting" carburetor to aid in starting, again because of the lack of accelerator pumps.

Jon

Yeah, I was kind of afraid that might be a problem, I figured I might have to put a heavier set of springs in them (the ones over the vacuum piston).

I am also considering EFI. I would just prefer something in there that looks like it could have been there in the '50s. I have a copy of Hot Rod Magazine from, I think April of '53 and there is a GMC on the cover with side draft mechanical injection that looks beautiful (to my eye anyway). I would just prefer it to look more mechanical than electronic. I have been toying with the idea of using a Pontiac Central Point (port?) Injection type setup with one solenoid to controll the fuel and use actual mechaincal injection nozzles for the injectors. Just an idea, would probably be a maintenance nightmare (not to mention a pain to get set up right). Then there's coming up with throttle bodies (been thinking of using the throttle bases off a Rochester or BXOV Stromberg). Of course this is all academic at this point, so I can have lots of crazy ideas and it doesn't cost me anything but a little time (unless I am actually crazy enough to try and build it). Just don't call the guys with the butterfly nets yet, okay?