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Stromberg Carbureators

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Stromberg Carbureators
#1
  This topic is about my 1980 Triumph TR7
handspiker Paul Handspiker
Toronto, Ontario, Canada   CAN
I need to know if there is some other carburetors I can put on my 1980 triumph tr7-2 litre engine.i don't like the stombergs.Thanks

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1492739 by handspiker I need to know if there is some other carburetors I can put on my 1980 triumph tr7-2 litre engine.i don't like the stombergs.Thanks

SU HIF44s will work nicely. You can keep your existing manifold.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

lgray001 Avatar
lgray001 Gold Member Larry Gray
Lexington, VA, USA   USA
1976 Triumph TR7 "POS-2"
1979 Triumph TR7 "The Money Pit"
The original British cars had the SUs. You can up the size of the SUs or what I did; I concerted to dual Weber 40DOCE side drafts. There re kits for both the Weber side drat and down draft carbs, but they aren't cheap unless you can find them on eBay as I did.

I had SUs on all my MGs and they worked flawlessly when they were balanced, but dash pot oil is always an issue. I lived in St. Louis where we had 100 degree+ summers and 0 degree- winters. Someone told me to use caster oil (not the brand, but the medicine). I thought he was nuts, but it worked well, even in Michigan in Winter.

Good luck,

Larry


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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1492739 by handspiker I need to know if there is some other carburetors I can put on my 1980 triumph tr7-2 litre engine.i don't like the Strombergs.Thanks

Paul:

The Zenith-Strombergs are more sophisticated than the SUs, and work well when set up properly. The SUs also work well. Webers and others are more difficult to set up, but can give you a bit more top end horsepower when properly jetted. You will be hard pressed to find another carb with as good a balance between power and economy as the SUs and Zeniths.

Any particular reason you don't care for the Zeniths? I have found that most people don't care for them because they get a bit bewildered by the various adjustments. My one complaint about them is that the rubber diaphragms can fail. The SUs are pretty much bullet proof in this regard, but SU had the patent on the piston design, so Zenith had to find another way to do things.

Whatever you do, avoid the Weber DGV carbs. They are good carbs but in the TR7 they require a "swan neck" manifold, which makes them heavy on fuel and lousy for power. There is just not enough room for a downdraft carb and a good manifold in the TR7.

Reconditioning your Zeniths is certainly the least expensive option.

Keep us posted.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

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sliproc Avatar
sliproc Kevin Quistberg E
Long Beach, california, USA   USA
This comes up from time to time, I don't know what the deal is with the with the Zeniths, I have them on two different cars and I love them. They're easy to maintain, easy to rebuild, and in smog happy California easy to dial in for any test they can come up with(and over the years they've come up with a lot of tests).

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1493201 by sliproc This comes up from time to time, I don't know what the deal is with the with the Zeniths, I have them on two different cars and I love them. They're easy to maintain, easy to rebuild, and in smog happy California easy to dial in for any test they can come up with(and over the years they've come up with a lot of tests).

I gotta agree. When they are setup well, they really perform well. Even the water chokes work as advertised. The issue seems to be that they are blamed for problems and get misadjusted until they really are a problem. The trick for me was getting the Haynes manual on them, so I could understand what all the features were and how to set them up. After that they always worked well.

There is a widely held belief that they are a real limiter for horsepower, and replacing them with just about anything else will free untold amounts of power. I have not found that to be the case, and have found them tunable enough for my purposes. There is a good selection of needles available, and I like being able to adjust the mixture so easily.

But that's me.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
Absolutely true about Strombergs, had them on my TR4 and then on my TR6. In spite of some emissions related add-ons on the TR6's units, in my opinion they actually became simpler to maintain and adjust. I have that same Haynes manual for Stromberg carburettors as well as a small blue vinyl covered back pocket sized book from INTERAUTO.

"Knowledge itself is power" - sir Francis Bacon

sliproc Avatar
sliproc Kevin Quistberg E
Long Beach, california, USA   USA
As far as performance goes, most of the big factory racing teams back in the seventies chose to stay with Zeniths(though highly modified) over something more exotic such as Webers or Delortos. Huffaker, used them in his TR-7s as well as his Jensen-Healeys (both cars were national champions).
The Zenith-Stromberg has a lot better history than reputation. If you stick with the Zeniths you won't be sorry.

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DerbyRam54 Neville Wardle
Branford, Connecticut, USA   USA
You might also be surprised at the availability of parts, far better than you might come to believe from looking at the major parts suppliers' web sites.

Visit the web site of the manufacturer at burlen.co.uk and you might be pleasantly surprised. Their reference catalogue is well worth the postage costs.

No connection save that of a satisfied customer.

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1493434 by sliproc As far as performance goes, most of the big factory racing teams back in the seventies chose to stay with Zeniths(though highly modified) over something more exotic such as Webers or Delortos. Huffaker, used them in his TR-7s as well as his Jensen-Healeys (both cars were national champions).
The Zenith-Stromberg has a lot better history than reputation. If you stick with the Zeniths you won't be sorry.

The Jaguar racing team gave up the SUs (2" throats, so they were the big ones) in favor of Webers. The reason was horsepower, much to the team's surprise. But remember that the Jags were double overhead racing cams, with lofty red lines.

The SUs and Zeniths are somewhat handicapped by virtue of the fact that the jet is on the side of the throat. Webers and Del Ortos have the jet in the center of the throat, which gives a more uniform mixture. It is therefore less likely that a single cylinder will be lean or rich compared to the others. This cannot be overcome with the SU/Zeniths as it is a result of the design.

For street use, this is not enough of an issue to worry about, especially since a) the throat is smaller (1.75" vs 2"winking smiley and is therefore less prone to mixture uniformity issues, and b) 90% of your driving uses only a small fraction of the throat area, further minimizing mixture disparities.

For the lower RPM ranges where you do almost all of your driving, there is no power difference and a street engine will not be able to take advantage of the high RPM superiority of the Webers. The factory did a good job matching the carb to the application.

If an owner wants different carbs, more power to them. But if you expect a sudden improvement in power or drivability by swapping out the Zenith's, well, forget it. I suppose if your Zeniths were worn out and on their last legs you would see an improvement, but at that point a rebuild would be much less expensive.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1493474 by Darth V8R
In reply to # 1493434 by sliproc

The SUs and Zeniths are somewhat handicapped by virtue of the fact that the jet is on the side of the throat.


Vance

I don't currently have a Zenith or SU to look at and none of my literature is showing a through the throat schematic but I'm surprised to hear this fact. I always thought the jet was dead nuts in the center. And I think of myself pretty up on Stromberg and SU carbs.

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1493518 by POW I don't currently have a Zenith or SU to look at and none of my literature is showing a through the throat schematic but I'm surprised to hear this fact. I always thought the jet was dead nuts in the center. And I think of myself pretty up on Stromberg and SU carbs.

Look carefully at the cross section. The jet comes up through the floor of the throat. As the air valve (aka slide) lifts, the jet doesn't move and so the air moving through the upper portion of the throat will be much farther away from the jet and will tend to be lean on fuel.

The engineers were very clever, however. Notice the structure called the "bridge". That is present specifically to minimize the mixture disparities across the throat. It introduces just enough turbulence to improve mixing of the fuel and the air without significantly reducing flow. Damn clever. But even with this trick, having the jet centered in the throat gives superior mixture uniformity, hence the wide use of Webers for racing. You can race Zeniths and SUs, but Webers will outperform them on the top end just about every time. On the street, not so much.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore


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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1493518 by POW
In reply to # 1493474 by Darth V8R
In reply to # 1493434 by sliproc

The SUs and Zeniths are somewhat handicapped by virtue of the fact that the jet is on the side of the throat.


Vance

I don't currently have a Zenith or SU to look at and none of my literature is showing a through the throat schematic but I'm surprised to hear this fact. I always thought the jet was dead nuts in the center. And I think of myself pretty up on Stromberg and SU carbs.

"On the side of the throat" is what was throwing me off. I thought by that you meant that if one was to look through the carb int the direction of airflow, one would see the metering needle/jet and therefor the airvalve off to one side. My mistake. Otherwise I see what you're getting at and I don't dispute the the fact that a side draft Weber would be better at WOT but I wonder if that would be true if both examples were sizes the same taking into consideration the bridge itself cuts down the CFM some but keeps the air velocity up. Also something I noticed in the Zenith diagram is the metering needle is not in the center of the airvalve but downstream a fair amount.

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1494052 by POW "On the side of the throat" is what was throwing me off. I thought by that you meant that if one was to look through the carb int the direction of airflow, one would see the metering needle/jet and therefor the airvalve off to one side. My mistake. Otherwise I see what you're getting at and I don't dispute the the fact that a side draft Weber would be better at WOT but I wonder if that would be true if both examples were sizes the same taking into consideration the bridge itself cuts down the CFM some but keeps the air velocity up. Also something I noticed in the Zenith diagram is the metering needle is not in the center of the airvalve but downstream a fair amount.

My Bad. Apologies for my choice of words...

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

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