Carb Conv Kit, Weber Single Downdraft conversion

[Mike]

Has anyone done a conversion to a single weber carb on a 1275 engine? if so, what were the results? My carbs have had it it appears that this conversion could simplify things.

Thanks,

Mike
58 Bugeye Sprite/1275

 

[SilentUnicorn]

all together now (sing)

" A pair of SU's to really make it sing" la Lala laaaaa


mark
(not a weber fan)

 

[aeronca65t]

Webers give quite a bit of freedom with tuning (assuming you're talking about the side-draft Weber). But they also require a fair amount of knowledge to get the various jets and emulsion tubes selected properly.
Really, SUs are more "forgiving".

The other choice is the downdraft 2GV Weber that some folks use on Spridgets and MGs. My MGB came with one. It works OK, but I am replacing it with two proper SUs.

To be honest, probably the best setup is the MG Metro single SU carb setup (a front drive car not sold in the US). Vizard says it makes more power than the twin SUs. Typically, it uses a 1.5" SU carb but a 1.75" can be fitted too.
They work well.
I co-drove a 1275 Sprite in an endurance race with this carb setup and it clocked 108 mph.

They are often available on e-Bay UK. Not so common in the US.

~HERE~ is a similar single-carb aftermarket manifold.

 

[regularman]

Re: Carb Conv Kit, Weber Single Downdraft conversi

Has anyone done a conversion to a single weber carb on a 1275 engine? if so, what were the results? My carbs have had it it appears that this conversion could simplify things.

Thanks,

Mike
58 Bugeye Sprite/1275

I am partial to the weber myself. Good idle, no synching of carbs, fairly simple 2 stage workings. I don't know if it hurts performance or not, but it seems to do OK on gas. Even hot rodding around I always get at least 30, I used to get 37 on the highway with the 4 speed and 3.90 gear, not checked it with the 3.55 and 5 speed but it should improve some. They have been putting webers on every kind of vehicle for years, especially the 4 cylinders and there is a reason, very reliable. So reliabel that Holley bought the rights to make it as the 5200 and put it on lots of small Ford engines. I saw 6 2 barrel webers on a Ferrari at the Eurofest last fall. They looked sweet and they were factory original.

 

[jvandyke]

Re: Carb Conv Kit, Weber Single Downdraft conversi

I took the Weber off my 1098 and like my SUs better. Smoother overall operation, much easier to play with and understand. MPG went from 24 to 34. This was one Weber on one car, not something to draw generalizations from, and yet... it's singing.....

 

[lesingepsycho]

Re: Carb Conv Kit, Weber Single Downdraft conversi

My vote is for the SUs. They sound better and feel better without a doubt. That being said, I currently have the DGV on my car. The first set of SUs I rebuilt were great! They went on my mom's MG Midget and the tuning was a breeze! It's not even that difficult so long as you have a PERFECTLY MATCHED PAIR. And I'm not sure I can stress enough how important it is that they match as best as possible. I was very meticulous on the rebuild and my rebuild time paid dividends on the install and tuning.

As it turned out, I never realized that for years my dad would just grab two from the carby bin and slap'em on there. Looking back on it, we were probably trying to balance carbs with completely different needle profiles, misaligned jets, different amounts of wear, maybe even emission controlled with pre-emission carbs. It's NO WONDER we never got the cars to run smooth!

Finally I gave up and got a Weber. Its out of the box tuning and performance was much better than the jumbled mess I was used to, but once I felt what a good pair is supposed to feel like I was converted! SUs all the way.

So why would I have the DGV back on then? Well the last set I did just as meticulous of a rebuild but once it was all said and done, I had a vacuum leak at the rear carb's throttle shaft. I switched back to the DGV because it was my daily driver and even though I have replacement shafts now, I haven't had a chance to make the swap back. Add to that the fact that I'm now piecing together a fuel injection system and there ya go.

JACK

 

[Gundy]

To be honest, probably the best setup is the MG Metro single SU carb setup (a front drive car not sold in the US). Vizard says it makes more power than the twin SUs. Typically, it uses a 1.5" SU carb but a 1.75" can be fitted too.
They work well.
I co-drove a 1275 Sprite in an endurance race with this carb setup and it clocked 108 mph.

They are often available on e-Bay UK. Not so common in the US.

~HERE~ is a similar single-carb aftermarket manifold.

I'm quite pleased with the performance of the single HIF6 SU
on my 1380cc motor. It's smooth and responsive.
A professionally prepared set of twin SUs like our friend Hap
sells would be my choice if I were starting over however.

 

[BuggerAll]

I'm also happy with the single HIF44 on my tuned 1275, super resposnive, super torque (better than the Weber 45, according to Vizard, and that's what you want on the street) and super reliable.

 

[bill_powell]

Get this book:

https://www.amazon.com/Tuning-Engine-Definitive-Performance-Economy/dp/1859606202

Good article on A Series Carburation:

https://www.minimania.com/web/SCata...e/Calver's Corner/DisplayID/1120/ArticleV.cfm

And on HIF Carbs:

https://www.minimania.com/web/SCata...pe/Calver's Corner/DisplayID/725/ArticleV.cfm

My advice: Research first, spend money last. It always comes down to how you use your car, and how much you want to spend.

FWIW, My daily driver:

 

[Hap Waldrop]

Well, since everybody has given their opinion, I will too I'm partial to the twin SUs, they just look right, and SUs are very simple carbs, so easy enough to tune for most folks, so if you want to rebuild what ya got, here's what I can do with them.

 

[Hairyone]

I've just a mod to my 1275 frogeye, to a single HIF44 (1.75") & it's great!!
From what I've read up on, this carb is good up to the 100 bhp mark. The single manifold works better than the BMC twin. It WILL out perform a Webber on economy & POWER except at high revs (more than 5K).

 

[texas_bugeye]

I just changed my 948 over from a down draft Weber 23-36 DGV to a pair of SU HS2's.

....
The single weber doesn't so much simplfy over the dual SU Carbs as much as it put all the problems in a single box. Not as easy to tune I have done them both. Plan on spending a few hours and dollars on jets and hours of tuning with the weber or leave it the way it comes and tolerate the almost got it state.

Would you like to buy a Carb?

 

[SilentUnicorn]

I just changed my 948 over from a down draft Weber 23-36 DGV to a pair of SU HS2's.

....

Would you like to buy a Carb?

Pretty unbelievable isnt it?

I am not totally against webers, they have a place. some folks are tinkers and can deal with the occasional adjustment that the su mechanicals need . Don't get me wrong a well set up pair can be pretty trouble free. the weber on the other hand is extremely trouble free. Some folks prefer that.

mark

 

[Mike]

Thanks guys for all the input. Now you have given me a lot to ponder.

 

[texas_bugeye]

Hey don't get me wrong that Weber served me well for 8 years with out a single problem.
Weber makes great carbs very wide range of adaptability.

But lets face it the DGV just doesn't like displacements less than 1500 2000 cc.
They work great when jetted, quick response so so fuel mileage, you can get a manifold for just about any engine you can think of. And there is where what I feel is the problem.
It’s a shoot gun approach to all thing carbureted. Throw a webber at it. For A Series apps the runners are sooooo long. With most of the A series manifolds when you shut one down there is a pool of fuel lying in the bottom of the manifold directly under the carb you will smell it in your garage for days and swear there’s a fuel leak.
If you’re not comfortable with carb work you need to talk to Hap. He can fix up your SU’s good as new

 

[jvandyke]

I took the HS2's out of the box of parts I got with my car (untouched for 22 years when the PO put on the Weber) and went through them this winter. I just took them apart, cleaned and spent some time "matching" them. I replaced no parts. I bolted them on and off I went. Sold the Weber and intake on ebay for $275. I don't know why people drop $700 on a Weber kit when SUs are so easy to play with, maybe I just got lucky. I'm sure they aren't "spot on" but I'm happy and the car is a blast to drive, that's all that matters really, isn't it?