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Triumph TR6 - Carburetion, SUs where there should be Strombergs.

Alas.

The newbie (me) has found out (as some of you know) that this LBC of mine should have Zenith Stromberg carberooteration fitted.

It does not.

What I HAVE discovered is that (as previously discussed) the DPO (dreaded previous owner) or his predecessor managed to fit SUs (at least they are 1.750") and make it run with the choke fully engaged.

Now, being the smart feller that I am, I figured out that one shouldn't have to run whilst the choke (enrichener actually) is fully applied.

Humbly, I delved into the issue. HOURS of research (oh, ok, a few minutes) online revealed that the brass nuts on the bottom of the SU carburetor is the mixture and allows fuel/petrol/gasoline to flow into the air stream.

The looser the nuts are the richer the mixture. The nuts were tight. Guess what? One has to use the choke then.

I'm now out "15 flats" on each of the mixture nuts and I just went for a drive.

Ahem. NO CHOKE APPLIED!!

bowing, thank you, thank you.

Jim (no chokes were harmed in this experience)
Jim Deatsch

Having an SU set up in place of the Stromberg set up is not in and of itself a bad thing. What you have there is a reasonably popular modification. I know folks what have parted with some semi-serious amount of brass for an SU set up on the TR250/6 motors.
SteveP

I would swap you my strombergs for a pair of SU
Steven

(sniffing the air here)....

Why do I feel, suddenly, that I'm not in as bad of shape as I THOUGHT?

I've bought a set of Strombergs (with intake manifold) off Ebay and will be installing them and calculating the differences.

I'll let you all know.

Steven,
Perhaps, just perhaps.

Jim (the SU Meister, sort of)
Jim Deatsch

It sounds to me that you may have had the wrong SU needles in your carbs. Or they were secured into the body of the dashpot too low causing it to be "lean". Pulling on the choke moves the brass tubular parts down and allows more gas in - to mix with the air. You can check the "lean-ness" or "rich-ness" on an SU by pushing up on the "lifter" that lifts the dashpot about 3/16". If it's correct the idle should rise from 700 RPM to about 1200 RPM, then it should drop again to about 400 RPM and not stall. Then it's correct.

After the Strombergs, you may want to go back to the SU's. Don't sell them yet.

Don Elliott, Original Owner, 1958 TR3A (with the original SU's still on)
Don Elliott

Thanks a lot Don,

More good information.

I don't plan on selling anything until I get the right carbs (whichever) running right. If that's the SUs then that's what will be on my car.

I'm not much into originality in this case but won't be hacking the car up in any event.

Jim
Jim Deatsch

From your description of the jet adjustment, you have HS6 carbs fitted as opposed to HIF6 units. Below is the URL for the HS6 conversion for the TR6 as sold new by Burlen. It has a complete listing of parts. The jet sizes for the HS6 carbs are the same diameter bore. You may wish to pull the needles and see what you have and how it compares taper wise to the BAG needles. I used to have a full SU jet needle book with identifiers and taper patterns, but it was stolen when someone broke into my MGB several years ago. I am sure that someone, somewhere out in webland has posted one, so sharpen up those searching skills and go find it. Just make a chart of the diameters at the different points along the needle. If I am recalling correctly for the .100 jets, there will be anywhere from 13 to 16 measuring points (needle dependant) at 1/8" intervals. Measuring point 1 is at the top of the taper and will be the largest diameter on the needle. Any measuring points beyond 13 are pretty much for entertainment value only since you are going to be at full throttle by the time those points would come into play. Throttle response can also be tweaked by using different piston springs and or damper oils.

http://www.burlen.co.uk/burlen-user/default.asp?Category=burlen&Service=CarbSpec&Veh=2298
SteveP

Steven,

MANY thanks for that information though the link appears to be nonexistant. Apparently Burlen no longer have such information on their site.

I'll delve into it forthwith.

Jim
Jim Deatsch

Jim:
I bought HS6's and installed on my car. Got a pair of BAG needles, and they're the ones you wanna get! The needles shipped with the carbs (ebay purchase) were BAB, and the car absolutely would not run beyond 3000 RPM. Like hittin' a wall. The SU's are simpler, and beyond that, I don't believe there is much difference in drivability.....that's my story and I'm stickin' to it!! :)

Rod
Rod Nichols

Que pasa "BAG" needles? Sizing label? Taper type?

This thing is running better and better all the time, the more that I futz with it.

I know all about you guys from Idaho. I lived (for 11 years) in N. Idaho (St. Maries) and loved it. Problem was the economy went to pot so I left.

So Rod, out with it. Whatsabagneedle?

Jim
Jim Deatsch

Jim retry the link worked for me just now
Bill Brayford

OK, try it just to the Burlen home page:

http://www.burlen.co.uk/

Do a search for Triumph TR6 (site can be a bit dodgy at times so if one way doesnt work, try another way to search). You should get 8 results. Select the CD Conversion set - FZX 3045. It will not provide details of needle tapers, but will give you a listing for recommeded needles, piston springs and dampers if you need to change any of those out.

BAB vs BAG vs KP vs KN etc. SU needles are identified by 2 and 3 letter combination codes. There are fixed needles and spring loaded needles and then there is the taper I described above. Each letter designates a particular set of tapers and whether fixed or spring loaded. I can't say for sure, but have a feeling that the BAG is a spring loaded needle. You "jet" the SU carb by using needles of different tapers instead of changing out idle jets, air bleeds, emulsion tubes and main jets like on a Weber or Dellorto, etc. In a corollary to taking a Weber or Dellorto, etc. jet and drilling it to make it a different metering size, you can turn down SU needles to make them equivalent to a different (read richer) taper pattern. The key thing is the smaller the measure points are in diameter, the richer the "jetting" at any given measure relative to that same point on other needles. Without jet needle charts, I cannot tell you what the difference is between the BAB and BAG needles.

On one of my long gone MGBs, I ran a set of HS6s. For that car, we determined I needed to use KN needles. Could not get my hands on a KN needle anywhere, but did find some KP needles. Turns out that there were two (I seem to recall it was only two)meaningful measure points that were different and we could do something about them since they were both larger (read leaner). We chucked those puppies up in a jewelers lathe and turned the KPs into KNs, fitted them and hoped to live happily ever after with that car, but then this woman in a Monte Carlo took it out when she lost control of her car on the freeway. Poor car was wadded up beyond reasonable repair.

SteveP
SteveP

Jim:
To give you further reading material, here is another SU info treasure box... http://www.teglerizer.com/cgi-bin/needle100db.cgi
Earlier threads dredged from the archives recommended the BAG needles, and I previously had BDB, not BAB as I previously wrote. Oldtimer's disease set in....
Here in Idee-ho & the West those needles have worked well from sea level (in Portland, OR) to over 6000 ftup in the Central Mountains. Joe Curto, in Neu Yawk supplied me with mine, you might contact him,
@ http://www.geocities.com/jcurtoinc/ By the way, the needle taper is stamped into the base...
Good Luck & happy moToRing!
Rod

Rod Nichols

and NOW it works dandy. Thanks guys.

I know the Teg. He and I corresponded a lot when I had my MkI Spit.

I'll be delving deeper into this SU/ZS deal. Though I've already bought the carbs (if the seller ever replies) I may just stick with the SUs since they are starting to run better and better all the time.

Thanks again folks, I do appreciate the time and info.

Jim
Jim Deatsch

This thread was discussed between 11/08/2003 and 13/08/2003

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