Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 09-21-2012, 10:03 PM   #1
Robert
Member
 
Join Date: May 2010
Posts: 99
Default SU Carb or Carbs

Does anyone have experience running SU's on a Model A? If so, which type is compatable/modifications? Does anyone have any manifold fabrication suggestions? I'm looking to run either one or two carbs on my Model A based speedster. The only major mod to the engine is a Snyder's high compression head. Besides Model A's, I am 'cursed' with a long time interest in English cars so SU carbs are not strange to me. Any help is greatly appreciated. Thanks, Robert
Robert is offline   Reply With Quote
Old 09-21-2012, 10:33 PM   #2
Kurt in NJ
Senior Member
 
Kurt in NJ's Avatar
 
Join Date: May 2010
Location: on the Littlefield
Posts: 4,794
Default Re: SU Carb or Carbs

Probably the most reasonable ones to find are midget/sprite, and mgb, I have both types and have thought of the possibilitys, they have a variable venturi that adjusts mixture to airflow so too large isn't as much as a problem as with normal carbs---I saw thislink that lists some of them, the earlier ones used in the 50s and the first year or 2 in the 60s have cork seals to prevent leaks---probably not good choices, the ones used in AH3000 are larger (4bolt) and have a rubber that probably won't like modern gas for long and are more rare and $$ ---you would want to follow the mg manifold with a balance tube between them, the mg maniflod doesn't fit well to the A block and ex manifold

Here is alink with an incomplete chart of mgb and midget carbs - http://www.teglerizer.com/mgstuff/SUcarbs.htm
Kurt in NJ is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-21-2012, 11:04 PM   #3
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,558
Default Re: SU Carb or Carbs

As an ooold Jaguar mechanic, I would use 2 S.U.'s from a 3.8 Litre X.K.E. as they would be about right for a 200+ cubic inch Model A. They're a simpler, more refined version than some earlier versions, with a much better choke system & much easier to adjust. I would use them without an equalizer tube, as you can adjust them down to a gnat's eyebrow They're a beautiful carb & oh! so SIMPLE! Bill W.
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 09-22-2012, 12:06 AM   #4
wensum
Senior Member
 
wensum's Avatar
 
Join Date: Apr 2011
Location: New Zealand
Posts: 418
Smile Re: SU Carb or Carbs

I know of two speedsters here in New Zealand, one with twin SU's and the other with twin Strombergs off an earlier Holden.
The owner with the twin Strombergs claims to have tried twin SUs without success, but the owner with the twin SUs races and drive long distances with great success.
In fact both cars go very well!
I think the twin SUs are 1 3/4"
Keith
wensum is offline   Reply With Quote
Old 09-22-2012, 04:13 AM   #5
dumb person
Senior Member
 
dumb person's Avatar
 
Join Date: Apr 2011
Location: South pacific island
Posts: 1,558
Default Re: SU Carb or Carbs

Is this link any help? http://www.jalopyjournal.com/forum/s...d.php?t=720811
The thread starts off as exhaust but quickly turns to the carb' in question. Personally i would use only one but i am weird.

Last edited by dumb person; 09-22-2012 at 04:15 AM. Reason: Clarification
dumb person is offline   Reply With Quote
Old 09-22-2012, 05:44 AM   #6
Terry, NJ
Senior Member
 
Terry, NJ's Avatar
 
Join Date: May 2010
Location: Bucks Co, Pa
Posts: 3,404
Default Re: SU Carb or Carbs

I had SUs on my TR3, Spitfire, and my Jag. Worst carb of them all! I hated them! Hard to adjust! Hard to synchronize, easy to go out of adjustment and I never liked putting oil in them every 30 days. Get an American made 2 barrel, Stromberg, Carter, or even a Rochester and save yourself a lot of grief.
Terry
Terry, NJ is offline   Reply With Quote
Old 09-22-2012, 06:09 AM   #7
2manycars
Senior Member
 
2manycars's Avatar
 
Join Date: May 2010
Location: Eastern CT
Posts: 2,719
Default Re: SU Carb or Carbs

Like a lot of model A stories, the SU carb is a great carb when not all worn out and needing rebuilding. I have a large single SU on my supercharged MGB, and have driven it many thousand miles in the past 3 years without touching it at all. It is one of the best carbs ever designed.
Attached Images
File Type: jpg blower2.jpg (70.9 KB, 71 views)
2manycars is offline   Reply With Quote
Old 09-22-2012, 06:19 AM   #8
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,000
Default Re: SU Carb or Carbs

I think I have a complete dual SU carbs/intake/exhaust set-up in my collection (...that I might also consider selling ) that came off of a Model-B racer . Either way, I can probably post some pix of it if you are interested in just seeing what it is.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 09-22-2012, 07:36 AM   #9
MARVIN, CT
Member
 
MARVIN, CT's Avatar
 
Join Date: May 2010
Location: Preston,ct
Posts: 76
Default Re: SU Carb or Carbs

Saw a picture a while back of a 60hp in a boat that had four SU's on it. Would look quite fitting on my 60hp that I put in my '52 MGTD. Marvin
MARVIN, CT is offline   Reply With Quote
Old 09-22-2012, 07:39 AM   #10
Keith True
Senior Member
 
Keith True's Avatar
 
Join Date: May 2010
Location: Epping N.H.
Posts: 2,388
Default Re: SU Carb or Carbs

For SU parts,repair and info there is a fellow in New York named Joe Curto that is very helpful.Most SU carb problems are SU owner problems.They turn out to be ignition problems,valve problems,filters,pumps,etc.They are almost a primitive carb.They really are a set it and forget it type of thing.If they are sucking the oil out of them they have internal problems,usually caused by somebody getting carried away with cleaning the piston/dashpot bores and plungers.I've had SU's that I've had to change the oil in because it was so old it turned to grease.I've really only worked on one SU problem that was an actual carb problem.The rest were other problems that were made worse by guys fiddling with the SU's.I worked on a Daimler SP 250 that the owner was sending to the shop every month to get the carbs set up.That's just not right.Turns out the dual point distributer was running on one set of points.But,if the shop monkeyed with the carbs it would sound better for a while.I can sit and think of a dozen more problems that had people tearing into their SU's when there was nothing wrong with them.They really made a slick carb for a Harley too.Then the S&S came out and everybody went to them.If I was going to use anything other than a stock Zenith,I would use an SU.
Keith True is online now   Reply With Quote
Old 09-22-2012, 09:49 AM   #11
Jim Brierley
Senior Member
 
Join Date: Jun 2010
Location: Temecula, CA
Posts: 2,908
Default Re: SU Carb or Carbs

I've never run them but they should do well. Keep in mind that the A has big cylinders and needs a big carb to feed them. I am running 3 of the little Stromberg 81's on my speedster, and they do well both in the power and the mileage departments.
Jim Brierley is offline   Reply With Quote
Old 09-22-2012, 10:05 AM   #12
Marco Tahtaras
Senior Member
 
Marco Tahtaras's Avatar
 
Join Date: May 2010
Posts: 3,099
Default Re: SU Carb or Carbs

I have limited experience with SU carbs but would think the Jag carbs would be a bit much. With that said, when I was about 18 I had an XKE roadster for a short time with triple SU HD8 (2") carbs. They were a dream for setup and performance. They were simple to adjust, sync, etc., and required very little after doing so. However it certainly helped having the factory shop manual which I still own.

On a Model A engine with a mild boost in compression but otherwise stock, it won't be able to efficiently utilize much in carburetion but I like the idea of SU side draft carbs and have thought about it.
__________________
http://www.abarnyard.com/
Marco Tahtaras is offline   Reply With Quote
Old 09-22-2012, 11:13 AM   #13
mmindling
Senior Member
 
mmindling's Avatar
 
Join Date: Jun 2012
Location: SouthEast Ohio
Posts: 125
Default Re: SU Carb or Carbs

Have a 71 RR Silver Shadow Coupe, which runs two SU carbs. They are great carbs - very simple and easy to adjust, very understandable. Synchronizing them is more a matter of the mechanical linkage being tight and properly adjusted, than a matter of individual carb settings. For the settings, I turn each carb adjustment to zero and then set them to the factory recommended set ups. The linkage, however, is another matter. There are a number of calibrations to pay attention to in order to be sure that the movements of the throttles are identical.

Using them on a performance Model A?? I'd recommend it, but pay attention to getting the proper intake manifold and be sure the linkages to each carb are proper. There are several publications on tuning SU's.

For now, I'm keeping the Zenith double venturi on my e28. It works fine.

Regards,
mmindling is offline   Reply With Quote
Old 09-22-2012, 01:16 PM   #14
d.j. moordigian
Senior Member
 
d.j. moordigian's Avatar
 
Join Date: May 2010
Location: Fresno, Ca.
Posts: 3,546
Default Re: SU Carb or Carbs

Quote:
Originally Posted by BILL WILLIAMSON View Post
As an ooold Jaguar mechanic, I would use 2 S.U.'s from a 3.8 Litre X.K.E. as they would be about right for a 200+ cubic inch Model A. They're a simpler, more refined version than some earlier versions, with a much better choke system & much easier to adjust. I would use them without an equalizer tube, as you can adjust them down to a gnat's eyebrow They're a beautiful carb & oh! so SIMPLE! Bill W.
I did some without the balance tube...it didn't like it. Ran better stock.
Even tried it with a small hole...no good. I think the MGB's or Tr-4's, Su's
are a better choice. Have a set at home for my B engine someday.

I like Skinners Union carbs...As an oold Jaguar mechanic...LOL
d.j. moordigian is offline   Reply With Quote
Old 09-22-2012, 05:09 PM   #15
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,558
Default Re: SU Carb or Carbs

Quote:
Originally Posted by d.j. moordigian View Post
I did some without the balance tube...it didn't like it. Ran better stock.
Even tried it with a small hole...no good. I think the MGB's or Tr-4's, Su's
are a better choice. Have a set at home for my B engine someday.

I like Skinners Union carbs...As an oold Jaguar mechanic...LOL
Yep! designed by a plumber in Jolly Old-------Bill W. (An even ooooooolder Jag fixer!)
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 09-22-2012, 08:29 PM   #16
wensum
Senior Member
 
wensum's Avatar
 
Join Date: Apr 2011
Location: New Zealand
Posts: 418
Default Re: SU Carb or Carbs

Attached is a photo of an A with twin SU's which goes particularly well.
As you can see, it has a Riley head and the basic block is a Claas which is an improved version of the model A
Attached Images
File Type: jpg Varied 030.jpg comp.jpg (70.7 KB, 116 views)
wensum is offline   Reply With Quote
Old 09-22-2012, 09:02 PM   #17
bettlesr
Senior Member
 
bettlesr's Avatar
 
Join Date: Nov 2010
Location: Florham Park, NJ
Posts: 361
Default Re: SU Carb or Carbs

I have a pair of HIF4's I am planing to put on over the winter. My son is going to weld me up a manifold and equalizer tube. I have a .100 over 7:1 engine with a touring cam. Hope they work out.
bettlesr is offline   Reply With Quote
Old 09-22-2012, 10:25 PM   #18
Lawrie
Senior Member
 
Lawrie's Avatar
 
Join Date: May 2010
Location: Qld, Australia
Posts: 3,246
Default Re: SU Carb or Carbs

What about a carb from a Harley,they are ment to run on gravity feed, and will feed a 80 cuin eng at twice the RPM of and A,and should be OK on modern fuel
Lawrie
Lawrie is online now   Reply With Quote
Old 09-23-2012, 07:06 AM   #19
Robert
Member
 
Join Date: May 2010
Posts: 99
Default Re: SU Carb or Carbs

Thanks for everyone's input. By chance,I found a set of 1 1/4 SU's from an A/H Sprite that I had stashed away many years ago in my warehouse-started welding up an intake last night. I will keep the 'Model A' world posted on my progress. Cheers, Robert
Robert is offline   Reply With Quote
Old 09-24-2012, 03:17 PM   #20
wensum
Senior Member
 
wensum's Avatar
 
Join Date: Apr 2011
Location: New Zealand
Posts: 418
Default Re: SU Carb or Carbs

I have a Daimler SP250 which runs on two 1 3/4" SU's, (2.5 litres) a 3 Litre Lancia Lambda on a single 1 3/4" SU and a Vauxhall 30/98 on two 1 3/4" SU's (4.25 litres)
I think the SU's you are thinking of using might prove too small?
Keith
wensum is offline   Reply With Quote
Old 09-25-2012, 06:14 AM   #21
ctlikon0712
Senior Member
 
ctlikon0712's Avatar
 
Join Date: Feb 2011
Location: Cocoa, Florida
Posts: 1,609
Default Re: SU Carb or Carbs

Bettlesr, could you or anyone else explain to me what a Claas block is? I know of B's, Diamonds, Gaz, and the German G28T.....
__________________
Wanted: Simmons Super Power Head
Craig Likon 1931 150B
ctlikon0712 is offline   Reply With Quote
Old 09-25-2012, 09:28 AM   #22
bettlesr
Senior Member
 
bettlesr's Avatar
 
Join Date: Nov 2010
Location: Florham Park, NJ
Posts: 361
Default Re: SU Carb or Carbs

ctlikon0712:
I have no idea what a claas block is. Try asking winsum, he is the one who mentioned it.
bettlesr is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-25-2012, 12:21 PM   #23
wga
Senior Member
 
wga's Avatar
 
Join Date: Jul 2010
Location: Land of Gracious Living
Posts: 659
Default Re: SU Carb or Carbs

Skinners Union? Anyway, the SU is a sliding venturi carb and is generally an efficient carb. Problems usually are worn out throttle shaft bushings, which will not allow you to adjust them properly. I'd use a machine shop on the throttle shaft bushing replacements for a rebuild, however the rest is very straight forward. All types of needles and seats available. Using a Unisyn to help balance them. A couple of
1 1/2 inch or larger should be great on that motor.
__________________
Henry Ford designed the flathead without the aid of a computer.
wga is offline   Reply With Quote
Old 09-25-2012, 05:13 PM   #24
ctlikon0712
Senior Member
 
ctlikon0712's Avatar
 
Join Date: Feb 2011
Location: Cocoa, Florida
Posts: 1,609
Default Re: SU Carb or Carbs

Your right, sorry, no coffee at that time! lol Wensum?......
__________________
Wanted: Simmons Super Power Head
Craig Likon 1931 150B
ctlikon0712 is offline   Reply With Quote
Old 09-26-2012, 06:38 PM   #25
Brendan1959
Member
 
Brendan1959's Avatar
 
Join Date: Jul 2010
Location: Melbourne Australia
Posts: 60
Default Re: SU Carb or Carbs

Robert
There is a link to my header story above, I have been running my SUs which are 1 1/2 for only a week or so, still fiddling with them, they seem to work well, you need to keep the monifold short so they clear the hood. Gravity seems to be enough to feed them as well, I bought an electric pump but have not fitted it. As I assume your are left hand drive you can adapt the stock linkage, I had to swap the carbs as the bowl clashed with the steering down tube.
Regards
Brendan
Attached Images
File Type: jpg su.JPG (148.6 KB, 87 views)
Brendan1959 is offline   Reply With Quote
Old 09-26-2012, 07:34 PM   #26
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,558
Default Re: SU Carb or Carbs

Quote:
Originally Posted by Brendan1959 View Post
Robert
There is a link to my header story above, I have been running my SUs which are 1 1/2 for only a week or so, still fiddling with them, they seem to work well, you need to keep the monifold short so they clear the hood. Gravity seems to be enough to feed them as well, I bought an electric pump but have not fitted it. As I assume your are left hand drive you can adapt the stock linkage, I had to swap the carbs as the bowl clashed with the steering down tube.
Regards
Brendan
Brendan,
BEAUTIFUL JOB! They look so perfect & at "home" there. Will you have room for the flat round paper element air filters?
I love to observe the fuel spray pattern at a steady 2500 or so RPM. You would expect to see a cone shaped flow from the needle & jet, instead, you see a fine flow across the entire raised bridge, almost as if the bridge had a razor thin slot across it. Amazing carbs & SO simple. They work on the CVVV principle. (Constant velocity, variable volume.) Bill W.
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 09-26-2012, 07:44 PM   #27
Brendan1959
Member
 
Brendan1959's Avatar
 
Join Date: Jul 2010
Location: Melbourne Australia
Posts: 60
Default Re: SU Carb or Carbs

Quote:
Originally Posted by BILL WILLIAMSON View Post
Brendan,
BEAUTIFUL JOB! They look so perfect & at "home" there. Will you have room for the flat round paper element air filters?
I love to observe the fuel spray pattern at a steady 2500 or so RPM. You would expect to see a cone shaped flow from the needle & jet, instead, you see a fine flow across the entire raised bridge, almost as if the bridge had a razor thin slot across it. Amazing carbs & SO simple. They work on the CVVV principle. (Constant velocity, variable volume.) Bill W.
Thanks Bill
I think they look good too, Air cleaners may be a problem as the front carb gets closer to the hood. I started making some bug screens last night. I like the look of ram tubes also, air cleaners will hide some of the carb, not sure what I will do. I have found some narrow air cleaners on ebay UK
http://www.ebay.com.au/itm/150628293...84.m1423.l2649

Brendan
Brendan1959 is offline   Reply With Quote
Old 09-27-2012, 02:17 AM   #28
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,558
Default Re: SU Carb or Carbs

Quote:
Originally Posted by Brendan1959 View Post
Thanks Bill
I think they look good too, Air cleaners may be a problem as the front carb gets closer to the hood. I started making some bug screens last night. I like the look of ram tubes also, air cleaners will hide some of the carb, not sure what I will do. I have found some narrow air cleaners on ebay UK
http://www.ebay.com.au/itm/150628293...84.m1423.l2649

Brendan
Brendan,
There's a lot of different configurations of the round filters, I'm sure you will find ones that will fit. Are those carbs the same bore as the early Jag XKE? The 3.8 L was 231 cubic inch with 3 carbs, so I think 2 would suffice on a Model A's 200 + cubic inch.
I hope NO one considers using some of the earlier, smaller S.U.'s as the old types with the cork jet seals & the rinky-dink choke contraptions are a pain in the butt to keep set up & synchronized & the inline throttle shaft, with it's "waffle" spring connectors are a pain. You've used the best design of the S.U.'s. Bill W.
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 09-27-2012, 04:00 PM   #29
Brendan1959
Member
 
Brendan1959's Avatar
 
Join Date: Jul 2010
Location: Melbourne Australia
Posts: 60
Default Re: SU Carb or Carbs

Bill
I have 1" 1/2" carbs, I thought they might be undersized , Monkeybiker worked out the cfm and it looks OK see below.


"I run a single 1-1/4" SU downdraft on a B banger. 110CFM. Ported, shaped valves and seats, good cam, Thomas head. I've run a 94 and although it was better at the top end it was far too rich at the bottom end. I will play with carbs again but we've just rolled down to Le Mans and back running the little SU just fine. I've a pair of the downdraft 1-1/4" I want to try and also a single 1-3/4".

Let's say 200ci x max 3000revs/3456 x 0.7 volumetric efficiency - which would be pretty good for a flathead banger. I make that around 121.5 CFM. Higher revving - say 4000 and efficiency at 0.75? Maybe 173 CFM.

A single 1-1/2" SU flows around 133CFM and a 94 is around 150CFM.You're two 1-1/2" will be plenty"


Regards
Brendan
Brendan1959 is offline   Reply With Quote
Old 10-05-2012, 03:02 AM   #30
wensum
Senior Member
 
wensum's Avatar
 
Join Date: Apr 2011
Location: New Zealand
Posts: 418
Default Re: SU Carb or Carbs

As far as I know, a Class motor is an improved Model A motor used in combine harvestors with shell bearings, oil pressure system and alloy sump.
I believe these were still being used or made after WWll and are considered highly desirable here and sell for quite big money
wensum is offline   Reply With Quote
Old 10-05-2012, 05:06 AM   #31
Juggler
Senior Member
 
Juggler's Avatar
 
Join Date: Aug 2010
Location: Phoenix AZ/Bath UK
Posts: 443
Default Re: SU Carb or Carbs

Quote:
Originally Posted by ctlikon0712 View Post
Bettlesr, could you or anyone else explain to me what a Claas block is? I know of B's, Diamonds, Gaz, and the German G28T.....
The G28 was fitted into Claas combine harvesters (and presumably other agricultural machinery?) and so is sometimes referred to as a Claas engine. Same thing.
Juggler is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 05:30 PM.