Pros and cons of various carburetors?

[nomad]

While on the subject I'm curious as to whether anyone has experience with Vizard's SU mods for fuel economy? Also, had a midget with a DGV that previous owner had fooled around with. Went like stink but smoked black and got terible gas mileage. An expert at setting one up would love them. I have one on a 620 Datsun pickup that improved fuel mileage and acceleration over stock. Just a matter of having them fit the application. Unfortunatly the ones for spridgets don't seem to as they come from suppliers.
KA.

 

[Luke_Healey]

I think my issue is that I understand how the SUs are supposed to work, and I've nearly converted the tune-up procedures to long term memory.

But if you have a set that doesn't work right, or has some wrong parts in them, they're hard to dial in if it's not obvious what's wrong with them. Mine are tight and don't seem to leak air, but I just think they could run better. Also, I'm finding that I have a different definition of 'runs right' than many people. Some people simply think it's fine if the car starts and drives. Others know the dark art of carb tuning down to figuring out which specific SU needle they want to run based on their style of driving.

Me? I just want something that is as close to proper OEM power delivery and fuel economy as possible. I'm not planning on racing the car. It already goes faster than its current suspension system safely handles. I think I got somewhere with the floats because the car starts cold and runs a lot better than it did when cold prior to that. I am going to drive this way for a while and see if fuel mileage improves.

The single SU looks like what I'd want to do in the future, using a new, trusted carburetor. I'm still trying to figure out what style of needle valves were in there. I wonder if they're not even proper for the car. I think prior to last week, the fuel level must have been too low in the main jets, which explains needing to drive around with the choke on for so long.

The DGV sounds fun. I'm used to acellerator pumps, and changing jets based on altitude since I have dealt with them before. They are more complex than an SU, but I think there's less room for error when you change out a jet versus adjust an SU one :wink:

It's good to know we have these options. I wasn't even thinking about a single bigger SU before I started the thread. I definitely don't want the sort of car I have to rev to get anywhere. I prefer torque over horsepower always, and have a habit of lugging all of my cars around at low RPM. Take-off power is my favorite rather than bleeding edge high RPM horsepower delivery.

Speaking of which, Friday when I was driving, I got a 2nd gear scratch which surprised me when I heard the tires bark. So something is getting better.

 

[BuggerAll]

I also vote for the HIF 44 - got one on ebay, already had most Vizard-recommended mods done to it - for about $60. Bought a Titan manifold from APT, had to change the needle once to dial it in (started with BDL, ended with BDK). It pulls like a horse, will put it on the chassis dyno at Carlisle to see what it's making (engine has a rash of other mods to it). Talk about simplicity of tuning. Made my own heat shield of sheet aluminum backed with thermal material and no problems whatsoever with hot start.

 

[Hap Waldrop]

Hey all, I've been unable to get on the forum last couple weeks, well post anyway and this is one of the threads I was chomping at the bit to post on, first off we're talking about a A-series engine here, not a 1500. Here's the deal when it comes to carb choices for the A-series engine, mostly 1275s, the twin HS2 set up is the best all aorund set up available for these cars, the downdraft Weber, while a great improvement to a 1500 car, is for sure a performance downgrade to a 1275, wrong intake design, not a very good carb to start with, and it cost the same amount as rebuilding your HS2 assembly to like new standards ($450 is what I charge for a totlaly cosmetic and mechinically restored set with a new heatsheild).

Ok on to other carbs choices for a A series engine, the single HS6 or single HI44, bottom line not a bad set up, but it less CFM that two HS2, so why folks do this is beyond me, and the fuel chagre still has to go around a corner like the downdraft and sidedraft Weber, where the twin HS2 set up is a straight shot. The side draft DCOE weber are good carbs, but other than maybe a tick more on top end, if even that, they offer no real performance gain, but they are royal PITA to work on and adjust, anmd very expensive, not really worth it in my book, eye candy at best.

People are mentally stumped by SU carbs, which normally means they would be even more stumped by either of the Weber carbs, because a SU carb has to be the most simple carb on the face of the planet, after all these folks used to make meat grinders If you look and study these carbs, you can clearly see there is no other carb any more simple to adjust and operate, yet they still confuse folks to the point they just want to open up a new shiney box and put a Weber DGV on there, which is a good back step in carb and performance to these cars, on the 1500, I can buy it, on the A-series engine, it is a cop out, plain and simple.

I'll rebuild your HS2 asembly like brand new for the same money as it takes to buy a Weber downdraft, and a lot less than a side draft DCOE set up and I guarantee you'll be happier. I built several members of these forum's carbs, here's a picture of the ones I did for Tony on his 63 Midget.

 

[jvandyke]

Now I'm anxious to try my HS2s on my '63 again and sell the Weber and buy something shiny.

 

[Hap Waldrop]

To further my thoughts on this thread, alot od you all have gave good solid advice on SU carbs here, and I can't add much to this. the roginal poster said he didn't think his throttle shafts were worn, unoless thay been built in last couple of year, I can prbably guarntee you both themshaft and the butterflies aha s significant wear, I don't probably a couple hundred rebuilds on HS2. and I count the ones on hand and not run out of fingers the HSs I've seen that don't need s new shaft and butterfly. Unlike the HS4, the HS's shaft rides directly on the aluminum of the carb body, and while I'm sure this wa a cosot saving measure by the factory, it ended up working out, since the brass shaft is much softer than the carb body, the waer is almost always limited to the shaft, so not very often do you need to intall bushing or go with a oversized shaft, where with a HS4 this happen with almost every rebuild.

That needle and seat assembly shown in earlier picture is not a grose jet, but it is totally the wrong size for a HS series carb, and that is why your float level is way off, and yes that should be addressed, even though you have the coveted stell levered flaot in which you can bend the tab to adjust flaot level, getting the right viton neelde and seat assemebly would be a good start. I buy all my SU parts form Joe Curto, because he has forgotten more about SUs than most of us will ever know, and when I buy form him, I'm buying from a guy who actually is rebuilding carbs like me, not some parts guy riding a desk or counter.

 

[Gundy]

Hey all, I've been unable to get on the forum last couple weeks, well post anyway and this is one of the threads I was chomping at the bit to post on, first off we're talking about a A-series engine here, not a 1500. Here's the deal when it comes to carb choices for the A-series engine, mostly 1275s, the twin HS2 set up is the best all aorund set up available for these cars, the downdraft Weber, while a great improvement to a 1500 car, is for sure a performance downgrade to a 1275, wrong intake design, not a very good carb to start with, and it cost the same amount as rebuilding your HS2 assembly to like new standards ($450 is what I charge for a totlaly cosmetic and mechinically restored set with a new heatsheild).

Ok on to other carbs choices for a A series engine, the single HS6 or single HI44, bottom line not a bad set up, but it less CFM that two HS2, so why folks do this is beyond me, and the fuel chagre still has to go around a corner like the downdraft and sidedraft Weber, where the twin HS2 set up is a straight shot. The side draft DCOE weber are good carbs, but other than maybe a tick more on top end, if even that, they offer no real performance gain, but they are royal PITA to work on and adjust, anmd very expensive, not really worth it in my book, eye candy at best.

People are mentally stumped by SU carbs, which normally means they would be even more stumped by either of the Weber carbs, because a SU carb has to be the most simple carb on the face of the planet, after all these folks used to make meat grinders If you look and study these carbs, you can clearly see there is no other carb any more simple to adjust and operate, yet they still confuse folks to the point they just want to open up a new shiney box and put a Weber DGV on there, which is a good back step in carb and performance to these cars, on the 1500, I can buy it, on the A-series engine, it is a cop out, plain and simple.

I'll rebuild your HS2 asembly like brand new for the same money as it takes to buy a Weber downdraft, and a lot less than a side draft DCOE set up and I guarantee you'll be happier. I built several members of these forum's carbs, here's a picture of the ones I did for Tony on his 63 Midget.

Dude, those HS2s of yours aren't eye candy. They are carb porn.
This all brings me back to an earlier inquiry about the single carb on my 1380. I'm saving up my pennies now for a set of your HS2s. I've always like the look and sex appeal of those twin carbs and now I know it's going to be the right upgrade for my BE from a performance stand point as well.
I'll have me a set of those before Alan gets back on the road. :wink:

 

[Luke_Healey]

Hap, I'll most likely be getting in touch with you if things aren't sorted out this season.

I'm happy to hear that my needles are wrong, because it sheds light onto a possible cause to my problem. I hate taking a shotgun approach to fix problems, but this has been one of them.

I guess it's not all bad. I have the thing perfectly timed and the main jet seats perfectly centered now. All things you'd want in place anyway.

It's just frustrating when you do all that and the car doesn't run any better. I was/am running spring loaded SU needles from a 1275 carb set. Now I can put my AN fixed needles and dashpots back on and see what happens.

Time to get out the Colortune yet again...

 

[Hap Waldrop]

Dude, those HS2s of yours aren't eye candy. They are carb porn.
This all brings me back to an earlier inquiry about the single carb on my 1380. I'm saving up my pennies now for a set of your HS2s. I've always like the look and sex appeal of those twin carbs and now I know it's going to be the right upgrade for my BE from a performance stand point as well.
I'll have me a set of those before Alan gets back on the road. :wink:

You can probably sell that HIF44 set up on Ebay for enough to get a twin HS2 set up We'll have to show Alan how the HS2s will out perform the DCOE, what we want for a good mountain road car, is something that will respond the second you hit the throttle, nice snappy throttle resopnse and the HS2s have that covered over the DCOE all day long. I'm currently working a new velocity stack/air filter combo for the HS2s, one of our FBCC club members is doing the CNC work for me.

 

[Hap Waldrop]

Hap, I'll most likely be getting in touch with you if things aren't sorted out this season.

I'm happy to hear that my needles are wrong, because it sheds light onto a possible cause to my problem. I hate taking a shotgun approach to fix problems, but this has been one of them.

I guess it's not all bad. I have the thing perfectly timed and the main jet seats perfectly centered now. All things you'd want in place anyway.

It's just frustrating when you do all that and the car doesn't run any better. I was/am running spring loaded SU needles from a 1275 carb set. Now I can put my AN fixed needles and dashpots back on and see what happens.

Time to get out the Colortune yet again...

Yeah, getting the jet centered on a fixed needle HS carb can be trying at times, the little tool in the SU tool kit helps but it's not always a savoir. Alot of the time, ( I learned this one from Joe Curto years ago) the early jet bearing gets wear on them where pull up against the bottom of the carb, and when you go to tighten them up that last little bit, they seat a bit crooked, the later jet bearing which is interchangable with the earlier HS2 won't do that and almost centers itself. You can straighten out the earlier jet bearings, but it takes a lathe to do it.

 

[Gundy]

You can probably sell that HIF44 set up on Ebay for enough to get a twin HS2 set up We'll have to show Alan how the HS2s will out perform the DCOE, what we want for a good mountain road car, is something that will respond the second you hit the throttle, nice snappy throttle resopnse and the HS2s have that covered over the DCOE all day long. I'm currently working a new velocity stack/air filter combo for the HS2s, one of our FBCC club members is doing the CNC work for me.

Selling my current set up ain't an option when it would mean down time. I shook the piggy bank this afternoon... it isn't ready to crack but it isn't empty. Keep us posted on those
velocity stacks and filters. Snappy response is there with the HIF6 but MORE gas sounds even better. :cooler:

 

[RonMacPherson]

Hap, I'm gonna beg to differ here. Perhaps it's just familiarity. but.....

I find Webers fairly easy to tune, been playing with 'em for better than 20 years now. Zenith Strombergs, Carters, Holleys. Mikuni sidedrafts all relatively easy for me. But the toilet maker carburetors and I do not have the best relationship going. Granted it has only been on a few cars, but......

 

[Hap Waldrop]

Like I said, SU stump people, and I have no idea why, the design is so simple, and there are so few part, and there plenty of things you can do to them to mod them for street and race.

 

[Luke_Healey]

Well, I gotta say that I think most of my problems lie in the needle valves in the float bowls being wrong. This last tank of fuel I'm near 30mpg. Power delivery is smooth and sputtering when cold is minimal.

I can start it up and just take off now, like a normal car.

The funny part is that the float lids I'm running right now have mismatched needles. One looks like the viton, and one looks like original SU. I'm going to order new needles for my correct lids and get everything adjusted correctly.

Like I said, the SUs are simple and easy to work on, but it's WAY easier if you have a working example to compare from. Faced with a set of crusty SUs would be pretty daunting for me. Especially when you don't know the history or if they even have the right parts in them. With the Weber DGV, it'd be easier for me to work with a strange one because I could just rebuild it and throw in the proper jets for my altitude and life would probably be good.

SUs are simple, yet so many combos of adjustments.

 

[jhorton3]

You know I found that my carbs had different needles in them too. Front looked like a Viton tip, and the rear looked like OEM SU unit. Mine were bought as rebuilt units. Swapping out for Viton tipped units helped a little, but not enough.