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Pros and cons of various carburetors?

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Luke_Healey

Luke_Healey

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I'm getting sick and tired of fiddling with the SUs I have on my Sprite. I've mentioned before that I had two of the same car at the same time. My ratty Sprite would run circles around my nice one. I'm pretty sure it's due to the carbs being out of whack on the nicer one.

The only difference was that the ratty car had grose jets.


Anyway, I'm thinking about spending some money and either sending my SUs to someone on this board who can finally rebuild them correctly for me so I can have the peace of mind they'll bolt on and work fine. That or the Weber DGV system. Or finally, splurge and eat macaroni for a month and get a DCOE setup.

So my question is what do I gain by running DGV over properly tuned SU HS2's?

And how complex is it to properly tune the DCOE system so the car hits some magical setting of economical, reliable, and fun to drive?

I'm still frustrated that the car takes forever to warm up and run well, runs either too rich or too lean, and just leaves me feeling unfulfilled every time I drive it.

I'm looking for a quick revving donut machine that'll get 30mpg.
 
I have very strong opinions based entirely on second hand knowledge gained from reading other people's problems (OPP) :wink: I am sure someone more qualified than I will pipe in.

Stay away from the Webers. They are fine carbs if you have the time, experience, patience and resources to set them up... but if you are already frustrated, you will be doubly so trying to sort out a DCOE.

Hap rebuilds carbs to better than new... but he generally has quite a back log. If you want to rebuild your own... a phone call to Joe Curto will be worth your time.
 
I'm going for a HIF44 SU single carb on my frogeye. Soon to be back on road for summer & using that. A much more modern 1 3/4" god for around 110HP I'm told & will outperform a webber under anything but racing conditions.
 
One SU that worked great and was easy to maintain does sound appealing. Who sells the appropriate manifold to bolt it up to our engines?

I don't plan on changing my engine in any way at this time, so I'm not in any sort of neighborhood of 100HP.

My main complaints are that I know how well my car COULD run with the SUs working right. I also know how to tune the SU carbs, but rebuilding them seems beyond my skillset in terms of knowing I'm doing it right and/or what the car should run like with properly tuned ones. I've got my Colortune, needle centering tool, and just enough skill to cause trouble.

Also, the car is always bogging down, which is really annoying. I'm only getting about 14mpg which to me suggests I'm running entirely too rich, but the exhaust doesn't smell that way. On takeoff I'm way rich. At high RPM I smell lean. It's just annoying.

Here is a video of me thrashing the car a bit, which points out some of my concerns about how long it takes to rev the car through the gears, and how it cuts out when I'm cornering hard to the left.

From 0-30 seconds, I'm pretty much running the car as hard as it's going to go. Accelleration through 3rd and 4th gear feels painfully slow to me.

1:46-1:48 shows how it bogs when I'm turning a corner in 2nd gear. Probably too rich again.

1:56-1:59 shows how the car cuts out when I'm turning hard to the left.

You don't really have to watch past that.. I'm just screwing around in a parking lot early in the morning.

4irN8yM" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>
 
Have you checked/set the floats? The bogging down in the corner seems indicative of a float problem.
 
You are describing worn throttle shafts. You can rebuild SU carbs. It is especially easy with two (you can use one as reference while you do the other).
 
Setting the float levels?

That, I have not done. I'm guessing it's past time to assume the previous owner did it correctly? :smile:

On the HS2, what size drill bit should I use to set the float tab distance with?


With a worn throttle shaft, if I spray carb cleaner around the throttle shafts, they should suck it in and case the car's idle to drop, correct? I tried that trick last year to find any leaks in the system and the car checked out as not having any air leaks at the throttle shafts or the connections to the manifold anywhere.
 
This doesn't have much to do with your carbs..but your Tach looks waaay off. At least listening to the engine vs the tach reading..doesn't sound right. At one point the engine bogs (I'd guess below 500 rpm) and the tach looks like its still at 1500+!
 
Luke -

Weber, Weber, & Weber !!

I was in the same boat last year. After 3 years of playing and fidgeting with those darn SU's - I yanked them in favor of a Weber 32/36 (not the dual 45's).

A) In my part of the country - I had one guy who could accurately work on the SU's (I think you need a MBA) and he was laid up due to illness. My local MG club could not help. Frankly, I think I'd have better luck asking to borrow money or sleep with someone else's wife than get help with these SU's.

I also had the tools and read the books. The words just didn't get into my brian.

B) I paid $450 total for the new Weber. In return I got a NEW carb& manifold adapter plate (in 2 days) that many gearheads (big iron) know about and like. Lot's of my friends know how to use / adjust. $450 is about the same as a quality SU rebuild would take from quality guys on this forum (in less time).

C) Minor modification was needed. I had to re-route the choke cable on how to connect to the 32/26. Not the end of the world. 2 hours (& I work slow) I was driving. Not a major deal.

D) Why 32/36 v. Dual 45's. The Dual 45's are for racers and speed nut's. I'm a driver. The 45's are two (2) massive fuel barrels. You still have to tune and balance. Where's the advantage?? The 32/36 is a one piece item (2 comparatively smaller barrells; stepped in size). Frankly - the car is pretty darm quick. I have no problem with the pep in my car - it NEVER ran that good (smooth AND accelleration) with the SU's.

I wanted new and a phone # on who to call with Q's so I bought new from carburation dot com. I already have many items that are more reliable than stock - so stock was not an issue.


https://www.britishcarforum.com/bcforum/ubbthreads.php/topics/568212/Parting_out_the_62#Post568212

The above member was / is parting out a car. Among other things - I saw he had a Weber 32/36 - now it's used. If you don't mind - you can save some money. I personally wanted new and was just fed up with the old balck magic that are SU's.

If you go the Weber route - buy the heat shield, had a vapor lock isue that it solved ($15).

Good luck -

George
 
Okay, You can get good results with Weber downdrafts(the DGV's) but takes a good basic setup to begin with.... Most suppliers(like Pierce manifolds, etc.) supply the Webers that are usually better than ballpark if you let them know your altitude and modifications.

I prefer the DCOE's.. Experience. There is a very good write up on Teglerizer's site(and maybe still links to other write ups) on dialing in the DCOE. For a small engine like the Sprite(under 2 liters) I would recommend a single 40 DCOE....
 
Right, you'll never get dual DCOEs to work on that small an engine. Once set up right, I don't think you can beat a single though. Unfortunately,m there are few techs qualified to "get it right" unless you are into all out racing. The DGV is a good carburetor although it has some compromises to polution control. You might find a source who knows how to set it for your conditions. Otherwise, it is not much easier that the DCOE. Anyway, I don't think you'll ever get a DGV to outperform proper SUs. Besides, they just look right. Honestly, there is no "black magic" about the darned things. They are about the simplest carburetor imagineable. From the video and your desrciptions, it does sound like float or needle vale problems. Look into those before spending several buck on a solution you may not like all that much anyway.
 
I spent most of the night scratching my head at how to measure the float height. My jets are sort of like the end of a ballpoint pen. There's a spring loaded ball in the end of them. I have no idea how to use a 1/8" drill bit to measure them since they'll never go that close low to the face of the float bowl lid.

I have two other sets of carbs sitting around, so I just took the easy route out and swapped in the floats and lids from another set. They have a different style of needle that I'm used to (triangular plastic needle.)

The car does run better (smoother mostly, and revs a bit quicker) now that I have the other floats in place. I'm going to drive it tomorrow morning which will tell me how fast it's warming up.

Here's what I had in there for needles originally. I think one of them is ruined, because pieces of rubber came out of it, and I don't think these are servicible since it doesn't seem to come apart:

3470250402_e7924e0b99.jpg


How do you measure the height and also what do you bend on to adjust them? It's not obvious since it differs from every other car or motorcycle I've worked on.

3470250494_f191e9ec1a.jpg
 
I've haven't heard one good thing about Grosse Jets from anyone who "KNOWS" SU carbs. the Viton tipped needle and seat are said to be THE way to go. That said if you're looking for parts, manifolds, headers, ..go to (aptfast.com)
 
Pythias said:
I've haven't heard one good thing about Grosse Jets from anyone who "KNOWS" SU carbs.

:savewave:

Let me be the deviant. :laugh: I wouldn't be caught dead with out a set im my SU's.

the Viton tipped needle and seat are said to be THE way to go.

They are OK, but no big deal, still just a needle that
wears.Just takes a little longer.

That said if you're looking for parts, manifolds,headers, ..go to (aptfast.com)
Click to expand...

------------------------------------------Keoke-- :driving:
 
I'd read that the modern grose jets aren't as good as the old ones?

For some reason, my previous sprite ran circles around this one and they were only 200 cars apart, both made in 1966.

as per this article on Moss Motors' site:

https://www.mossmotors.com/graphics/products/PDF/378-470.pdf

It looks like my floats are not adjustable, and instead you use paper washers to shim your needle valves in order to get the appropriate float height?

The brass pins that hold the floats into place are frozen in my case, They almost look like they're bent somewhat. Is there a safe way to get them out without breaking the pot metal of the float chamber lid?
 
Luke_Healey said:
How do you measure the height and also what do you bend on to adjust them?
Click to expand...

Got this very cool little book last month - <span style="font-style: italic">Tuning for Speed and Tuning for Economy. </span> (1968) Our old friend Robert Bentley

here is what he has to say

https://www.cnob.ca/index.php?pr=Car_Stuff&nosessionkill=1

(sorry you need to go to a link - can't figure out another way)

cheers
 
3471044902_d51112d85f.jpg


As you can see, as per the diagram in your file, my floats look WAY out of whack. The fuel shuts off at about that height.

Someone online mentioned you can scribe the side of your fuel bowls at some depth from the top and hook fish aquarium tubing to the bottom of the bowl where the main jet is supplied fuel. Then using the tubing bent up around, you can turn on the key to get the fuel pump flowing and see how high the gasoline sits in your tubing, to verify that the fuel level is where it should be.

It looks like Moss and VB only sell these stepped style floats rather than ones with straight arms on them.


One thing I hadn't thought of: Have any of you seen needle valves like what I have in there? They might be totally wrong. They are a spring loaded cylinder that pushes up on a bigger cylinder which seals it to a brass jet. They dont' come apart as far as I can tell. I'd never encountered this style before.
 
Using the tube along side the float chamber was how I did it on motorcycle carbs.
My Grose jets don't look like those. I've not yet run my HS2s so can't help much.
 
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