ctlikon0712
Well-known member
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.....
SU Carb or Carbs
- Thread starter Robert
- Start date
wga
Well-known member
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.
1 1/2 inch or larger should be great on that motor.
ctlikon0712
Well-known member
Your right, sorry, no coffee at that time! lol Wensum?......
Brendan1959
Member
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
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
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BILL WILLIAMSON
Well-known member
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.
Brendan1959
Member
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/150628293012?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Brendan
BILL WILLIAMSON
Well-known member
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.
Brendan1959
Member
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
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
Juggler
Senior Member
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.