Identifying carbs

HOUSEQUAKE

HOUSEQUAKE

Well-Known Forum User
I have twin carbs and want to know which ones I have?

1.75" or 2" SU? HS or HIF?

Where do I look coz I can see knack all on em
 
They should have a little i.d tag on each. Normally screwed to the float bowl or under the the piston dome. Should be able to tell by those if you have the no's stamped into them
 
If memory serves me right....

The throat diameter on the front of the carb will be 1.75" or 2".... if you can find a ruler when you need one.

and

HS carb has a separate fuel chamber set off to the side of the carb with a flexi pipe going underneath to the jet, while the HIF has an integral float chamber that sits underneath the carb.

I'll go and check in my book!
 
Early HS SU's had the float bowls seperate like these


SIE0083.jpg


Whereas the later HIF look like these with the floatbowl built into the underside of the carbs

HIF44.jpg


Obv they came in diffi sizes which is where the 1.75 and 2" comes into it
 
housequake your carbs are 1.75 for sure but i can not remember which type of SU they are,but the guy you got them from said they came from a triumph i think.
 
:S30: some triumph cars had 1.5 hs su carbs and some had 1.75s triumph 2000 2500 had 1.75 dollys had 1.5 i think? yours prob 1.75 the mesurement is take from the iner side of the carb but the outer should be close. 2.0 hs su will look a bit dumppy as they have a bigger top to them normaly

martin
 
Carbs

Thanks for the replies guys, away on a course so haven't had chance to look yet but thanks all the same
 
The HIF carb was designed with the float bowl on the bottom to reduce the problem of fuel surge/starvation on cornering. It has a spring loaded needle (self centering) which can cause wear on the jet. This is the SU of the 1980s fitted to Metros etc. HIFs are often refered to as 4s or 6s this is the number of 1/8s of an inch bigger than 1 inch.
ie HIF6 = 1 3/4. Metric version measured in mm diameter of the engine face bore. The intake bore is shaped to create some ram effect.
Dating the car they came off will be a big clue to the type of SU.

I think the tags on the carbs give the details of jets and needles.
 
John, as far I remember the tags on the carbs actually identify the carb. From mine I was able to cross-refer to an SU listing which said what they were HD8 and used on 1966 2.2 Rover TCs.

Mine are quite strange because they do not have idle mixture adjustment, no screws at all, only throttle and choke adjustment.
 
Should be an AU-something number on them I think. The people to talk to about spares etc are Burlen fuel systems. They bought the SU brand and have a pretty extensive website of info and bits.
 
Rob,
Tick over speed is normally set on single SUs with a stop on the thtottle spindle cam. I haven't bothered with this on my zed. I balanced the two and then set the tickover using the datsun adjuster on the linkage bar to open both carbs together.
Perhaps the Triumph set up was the same as the zed and set the tickover together. I'm sure the parts are available to retrofit if you want. They only clamp on the shaft.

There is a lot of tuning potential with SUs. Simple porting mods can take a stock 1 1/2 su from 130.3 cfm to 169.3 cfm on a flow bench. Considering that one barrel of a 40s weber flows 175 cfm this is good going. A stock without mods HIF6 flows 240cfm and a 45 weber barrel just pips it at 242. Looks like a good cheap simple to set up option.
 
I don't have a problem with my carbs and can set tickover no probs.

I'm just saying here that the 'tag' identifies the application and that mine haven't got a slow-running mixture adjustment screw.
 
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