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MG MGB Technical - Thoughts on HS6 conversion ????

Hi everyone,
Havent been on here in a while. I have a 79' MGB which currently has the weber 32/36 DGV on it that I have nothing but problems with getting it to run right. So Im wondering what people think of the HS6 SU conversion. Im even contemplating just getting a good rebuilt Zenith ! Just so it runs right. Im not going to get into detail about the weber, I have no questions about that, just curious what carbs people had before the hs6, differences etc, worth the money ? Also if anyone is looking for a nice 32/36 DVG make me an offer, it includes the manifold. Im done fooling around with it, I bought it new at moss's car show in Jersey. One good thing about that carb is that it starts right up all the time, cold or hot. Now I know that twin su's would be nice as well and I actually bought a very very nice pair that looked immaculate off of this site and just had clearence problems that would of easily been fixed if I wasnt young and stupid and trying to get my baby on the road asap and getting into the whole weber hype. Im about 6 years older and I still just want my baby to run, how much of a difference is there anyway in power, the dgv's butterfly valves are a lot smaller and only one operates till you open up the throttle a lot (sorry forgeting the name for that at the moment) So if you get a steady Zenith with it being rebushed it should be better... Steady idiling and power. So I would like to hear your guys input and if you feel the same was as I do, or any offers on the carb or if anyone has a nice hs6 or refurbished zenith etc would love to hear what you guys have to say. Or also keeping the sensor that warms up the air on the zenith carb attached to the HS6 for easier cold starting... etc, anyway like I said just curious ...
James

I don't own a Weber. This is only an opinion.

As far as I understand there's nothing *wrong* with a Weber. A new set of carbs is an expensive step to jump to. It would be cheaper and more fulfilling to ask the members on this board if they know of someone in your area who can set up your Weber for you. As I recall, there are multiple jets and valves which can be changed out, and the right combination can be difficult to find for a novice. However, there are many people who do get them set up correctly and like the carburetor very much.

By the way, the point that only one throttle opens up until you give it a lot of pedal is a good thing. When a car is running at lower rpm's it doesn't neccessarily have enough air flow to pull a good vacuum through two venturis. So you have to enrich the mixture to get it to run alright at idle and low rpm. The primary/secondary throttles, as the DGV has, addresses this issue quite nicely, and was a well accepted practice among downdraft carburetors until fuel injection took over the world.

In my opinion, this is the drawback with dual SU's. It's my uneducated guess that the motor can't efficiently draw fuel through both carburetors until it gets some revs going. The Haynes manual tells you to periodically rev the motor when adjusting the mixture. I believe this is to clear the manifold of pockets of fuel which have settled out of the mixture because it's so inefficient at that speed.

If you go to the HS6 SU's, you'll be compounding that problem because they have even bigger venturis. *In my uneducated opinion* that carb set would be best for motors who are constantly in the high rev range - like a track car, not a daily driver.

Before you go spending several hundred dollars on SU's, and have to deal with the clearance issue between air filter and brake booster, take the plunge and have your Weber set up professionally. Even if you have to drive to New Hampshire, or New Jersey, or wherever it is Glenn Towery works out of, I think it will be an investment of time and money that'll bring a much better return than trying to set up HS6's.

Sorry to blather on so long. I must switch to decaf in the mornings.

Best wishes,

Matt K.
Matt Kulka

I go along with Matt's comments provided of course there is someone reasonably near to you who can set up the Weber first time and not drain you of pots of money if he doesn't really have the experience. The jet sizing for the Webers are well documented and provided the correct ones are fitted then setting up is easy.

It won't however give you any better performance that the standard UK SU H4 set up which is reckoned to be about optimum for all but the most highly tuned Bs. If it were me, I'd check the SUs, bush, re needle and jet them and run with it. They would provide you with probably the best performance from your motor consistent with being fairly easy to set up and holding tune almost indefinitely.
Iain MacKintosh

James,

Call BritTek,www.brittek.com, 1-800-255-5883.

They work with Webers a lot. If you know if your engine has been modified or is standard, they can help you by providing the correct jets and needles.

They are very knowledgable and a pleasure to work with. Additionally, they have a great tech tip sheet for setting the weber up.

I set mine up 6 months ago and haven't had any problems. I just haven't gotten around to rebuilding my strombergs and replacing them yet.

Now if you want to get a little better throttle response, especially at the lower end, look into switching out to the Strombergs. Stay away from the zenith, in combination with the manifold, it was a compromise of a carb from the beginning to meet the US smog requirements.

New Strombergs are also available from the usual sources. Their cost is a little higner than having someone rebuild a pair but then all of the parts are new.

I hope this helps

Cris
Cris DeYoung

I have SUs and Webers (both DCOE and DGV). I have to say that the DGV is my least favorite and in fact, it's sitting on a shelf in my garage. For everyday use I prefer the SUs. I've raced 'As and 'Bs with a DCOE and for my use, I've gone back to SUs even there. I run HIF4s on my '74, but have built a set of HS4s for next year. Unless you have a big bore engine in mind, a set of 4s (HS or HIF) would be plenty; especially for a '79. I've only had one car with a Zenith, but it ran well enough.
Kemper

James

I put a HIF44 carb with Austin Marina manifold on mine and have had 0 problems in almost 2 years it gives me more power than the stock setup with no midrange problems that I've heard with the webers.I get from 26 to 30 mpg depending on how spirited I drive I hope this helps
Pat
patrick bailey

James, since you already have a set of SU's it would seem that you have what you think you want. If your clearance problem was with the air filter, see if JC Whitney still sells an air filter for the SU's. It is thinner than normal and solved the clearance problem. Let me know how much the shipping will be on your DGV to zip 81212. You too Kemper, and anyone else who is tired and ashamed of their DGV's.
rick

James. I believe that you are speaking of the HS-6/HIF-44 installation on the existing Z-S intake manifold. This conversion has been mentioned before and people seem to like the SU as compared to the Z-S. The problem has been the combined intake/exhaust manifold which is not optimized for power. Pat's use of the Austin Marina intake seems to be the best way to go.

The other alternative is twin SU HS/HIF-4 carbs in an early manifold. The people I know who have done this speak of the conversion highly. It does require special air filters to clear the brake servo on the late model cars. Much information in the archives on this conversion.

The DGV series carbs are legal, here in Arizona (or at least are allowed) on cars requiring emissions testing. Your conversion to a single SU would be allowed, but twin SU conversions are not. Hence, the Weber conversion, which cost less than the single SU, has been popular around here and I am running it on two of my cars. Still, I would prefer twin SU HS-4 carbs myself.

The DGV seems to be hard to find right now with rumors that it has gone out of production and that the prices have gone up significantly. Thus, a running DGV should be worth some money on E-Bay if you decide to do a converson. But, do all your research before you make your final decision, including spending several hours in the archives.

Les
Les Bengtson

Hey guys,
Yea I have looked through the technical Archives before and am in them as well in regards to the weber. I also do not have the SU's anymore, thought I mentioned that. If you do read the Archives you will see how much of a pain it is seting up the webers and how you can never really get it running right, and how it was never really meant for the car, anyway I just found a great deal on a Zenith brand new, curious about purchasing it. Its cheap enough to where I could hold on to the weber too. Ill give brit-tek a call as well, curious as to what they have to say. Never knew about the austin Marina manifold, thanks for the info. But probably will run the regular manifold on it till the summer time. Still curious about people running the HS6 instead of the Zenith. Differences etc ... Or people who have drove a late model with SU's Weber Zenith HS6, differences between them good bad etc... Not racing cars, standar street cars... Thanks guys, figure this could help other people out in the future with figuring out what to do. Oh I figure the Zenith would run a lot better anyway without all the smog equipment that I took off of her. Anyone know of running the ram pipes with a filter on it ?
James

I'd go with the SU HS4s if regulations where you live allow. the twin SUs were used up until the end of production in the UK, with the later spec dizzy it even made a little more power than earlier cars.
dave

Street cars: '76 midget, '77 'B - both with a single Zenith. The Midget Zenith was the original with about 50,000 miles. The 'B Zenith was as new. Both ran well enough; the same, in fact. Both started, idled, and accelerated as they should. '62 Mini with single HIF44 -ran very well

'74 'B with DGV -wandering idle, unstable mixture.

If I was stuck with the late model 'B manifold, I'd buy a new HIF44 to replace the Zenith (nothing wrong with Zenith, based totally on my preference for SUs).
Kemper

Thanks Kemper,
Yea have the same problem with my DGV and the only problem I had with the Zenith was a high idle (needed the throttle shaft rebushed, was rebuilt besides the rebushing). Other than that it was fine. Like I said the only good thin with my DGV was it would start right up, no cranking. I definetly think im buying this new zenith. Maybe Ill hold on to the weber for a while, sell it and get either the hif 44 or hs4 su's, anyone elses experiences with these carbs in comparison ? I know for one thing, tuning a single zenith is a piece of cake ! Better than trying to tune a weber yourself, or syncing twin su's or zeniths for that matter. Anyone have any specs to a stock car running these different carbs ?
James

Another point is, on a stock car with nothing else donw, how much does the performace really change ? I mean we are talking about a 1.8 litre engine, we all know that a super charger or a v8 conversion is the overall easiest ?(not know from experience) thing to do. We all know its an MGB not a TR6 MGC Healy etc... Granted we all want to tweak the fu*k out of our cars, but when running just about stock everything what is the difference, wouldnt changing the headers, and exhaust have a more benificial affect. Which then could be seen probably in the hs4's favor to perform better ?
James

oh just to get this thread going crazy as it always does when talking about supercharging a MG, you guys hear about the super turbo charger system being put in the new VW's. Its only time before someone finds a way to try and adapt that system to the MG. For those of you that dont know, the super charger is on until it reaches the point where turbo lag really doesnt happen and the benifits of a turbo outweight a supercharger and a mechanisim switches over to the turbo and simultaneously switches off the supercharger. Now I have hear that this was done in cars in the past, and also in piston driven airplanes so that they can go higher in the sky, but I think those where used in unison with each other and not switched off.
James

Kemper I talked with a very knowlegable mechanic who has converted B's with the Weber for years. He told me the Weber runs way to rich and the primary jets are the cause. You have to rejet it to get your idle correct and to obtain a decent gas milage after you convert. I get about 18 or 19 and he says I should be getting high 20's with the DGV. It is something you should consider, me? Im converting to a new motor, either a V8 or V6.

Chuck
CW Strong

James- My nickel's worth: The Weber is a PIA to be avoided. Your mind set going to SU is good instinct me thinks. The 1 3/4 SU is only marginally "better" on a street B over the 1 1/2, and a heck of alot more dolores. I bought a new set of SU 1 3/4 from an OZ dealer for $700 for the cross flow.A rebuilt,rebushed set of 1 1/2 SU runs less than $200! On me other 3 B's I have rebushed, rebuilt, re-needled SU 1 1/2. Use the conal K&N on 74 plus mgb roadsters to clear the servo. No Problem and a really sweet, dependable, steady carb. Once correctly adjusted, these babies just hold set for years, no kidding! FWIW, the 79 LE purchased 3 years ago came with a Webber DGV 32/36. What a headache and time loss. I regasketeed, rejetted, played, prayed and cursed the sucker to no advantage. Finally sold all on e-bay and bought the K&N conals with the proceeds. Car runs like a scalded cat, idles at 650 steady, and accelerates evenly to 5500. Yes it's a tad finnickey in cold, but full choke works well to start and in 5 minutes it's happytime at the OK carral! Vic
vem myers

I have a heavily modded street-driven 69 B with HS 6s. They run well and I like them. I run the car pretty briskly so don't have low-end concerns.
Art Dodge

The rule makers allowed me to go to 1 3/4" SUs and I bought a pair of 240Z dome top SUs. Cleaned them up, used the MG float bowl indexing blushing to tilt the float bowls at the correct angle. Very nice carbs better casting than the British carbs, no vacuum dump in the butterfly disk.
Lee Bradley

Lee, Did you have to put on a fart can and blue headlights to get it to run right? :)
Art dodge

No headlights but have a Flow Master. ;-}
Lee Bradley

James,
bummer about the weber, supposed to be a nice set up.
if you can't get 'er dialed ( I would recommend trying to the "color tune" system before scrapping $700.00 )
you may want to go with the HI-44.
Did you hold onto the original manifold?
The Z-S is not always the easiest carb to deal with, I myself am probably going to the HI-44 soon, my Z-S is mismatched to my car ( donor from TR-7 ).
And I can sympathise with the weber issue, on my spitfire it took almost as much cash to get someone to dial it in as the unit cost. Though that was the touchy thoroughbred DCOE, don't know much about the DGV, anyway, all the major suppliers seem to be pushing the '44 as the answer to zenith prayers.
best of luck.
JIM
J A Kelly

From my experience, I have found twin 1.5" SU's are a huge improvement over a single carb. set up (more torque and freer reving), while twin 1.75" SU's did not make a noticeable difference on a standard engine. The twin 1.75" SU's come into their own with much modified engines, particularly with a LCB extracter exhaust system (which also increases torque a fair amount). I have tried these as individual changes, not wholesale, to judge their respective improvements, and would whole heartedly recommmend twin 1.5" SU's and a LCB extracter exhaust system on a standard engine. This is a good standard road use set up for everyday use. The twin 1.75" SU's with an engine that has all the works gives me 125 hp at the rear wheels, but there is nothing to speak of below 3000 rpm! Not really suitable for road use, unfortunately. P.S. do not mention fuel economy with these mods. Matthew
M French

Thanks guys,
Well I bought that Brand New Zenith carb off of ebay, just waiting for it to arrive. It was way too much of a deal to pass up. It is though for a tr7 is what they were saying, New needles ? jet ? I still have my old zenith which I did a rebuild on just before I took it off for good so I can swap those. And yea id love to use a pair of 1.5 su's. But I really just want to get her running right again. Its been too long. Like M French said, more tourque and quicker revs was what I was looking for, but I bought the weber. Oh and the reason I am not putting the original zenith that I rebuilt on is because it needed to be rebushed.
James

James,
If TR-7 unit comes complete with water choke,
be aware that some of the bits are not in the same place as they are on the Mgb version,
if you have any questions let me know and I'll fire you a picture of my unit for visual comparison.
Jim
J A Kelly

Jim,
Yea that would be greatly appreciated ! Dont know if its a pic you already have taken but if not, could you take a pic of the electrical connections on the passenger side in the engine bay, fuse box etc? No clue what the PO had done to the thing, and I have never really checked, I hate looking at schematics, because I never know if im looking at it the right way, which side is which, ... So if your going to run out and snap a pick it would be a huge favor from one James to another... Thanks,
James
James

FWIW: I converted onver to a single HS6 (Volvo) and ditched my ZS. I wouldn't use antoher ZS, too much trouble. The ZS is set up for a car with smog equipment and as soon as you take off the emissions, the carb is no longer set up right (ie needle, or metering). The HS6 made a HUGE difference in my car. The emissions were removed, and the ZS was a tad worn. I'm still dialing in the needle choice, but with a richer needle (maybe a tad too rich) the accelleration is fantastic, and steadily and easily reaches 5K RPMs. With the ZS I always felt that there was more potential in the engine, and Indeed there is.

Doug
Doug

This thread was discussed between 14/10/2005 and 24/10/2005

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