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TR2/3/3A carburator decisions for TR3A

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I ordered new caps, rotors, plug wires, plugs and even a new pertronix, got a spare coil too. that should cover it

Hondo
 
I have a ton of Webers, both currently operational and in the past and my advice is to stick with SUs unless you are after engine bay candy for bragging rights.

There is no real advantage to Webers on a street engine and the inevitable disadvantage that they need precise setting up, a task few are capable of doing properly.

I think I have a set of Webers and manifolds for a TR3-4 kicking around in the garage somewhere if anyone is dying to try.
 
billspohn said:
There is no real advantage to Webers on a street engine and the inevitable disadvantage that they need precise setting up, a task few are capable of doing properly.
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Plus having to change jets on the side of the road, if you drive a large change in altitude. At least one of our local club members decided it wasn't worth the hassle after VTR 2001 in Breckenridge, CO (elevation 9000+ feet, depending on which side of town you are on).

ISTR Kas Kastner wrote that he could get just as much power with HS6 as with 40 DCOEs. Of course, he may have been a bit biased.
 
Yes, elevation change is where any constant depression carb shines. It doesn't matter a huge amount normally, but if you change elevation 8000 feet, that's going to throw out any fixed jet carb pretty significantly.


Understand that I have nothing against Webers - think they are excellent carbs (I'm running a total of 8 on my cars right now), it's just that they aren't always the best thing on the street, and far too many are stuck on otherwise unsuitable engines, and are never properly tuned.

They can be run on engines without downside when well set up - one example (of course that's one of my MG engines, not a TR....):

mgatc.jpg
 
DrEntropy said:
This is always a "fuzzy" topic.

The Webers alone are not gonna pump up the HP output much. They do have accelerator pumps, unlike the SU's, and give the seat-of-the-pants effect of <span style="font-style: italic">seemingly</span> more power. To gain HP, the whole engine whould need to be considered: cam, compression, CC'd head, ported intake & exhaust runners... Hondo went through the drill and dialed a set into compliance. It's a slog of a process, costly as well.

The SU's are VERY efficient devices, not to be dismissed. IMO it ultimately comes down to personal cost/benefit ratio. On a TR3 I'd stick with the SU's.
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There's a lot to be said here, though I will say Webers will give considerably more power just as a bolt-on. they simply have a larger area of flow (if you use two DCOEs).

When driving on the street, it's exactly the "seat-of-the-pants effect" that makes them special.

For real power of course the entire engine should be done, but an increase in acceleration and top speed <span style="font-style: italic">is</span> achieved by using DCOEs. More is found by doing the rest like compression, valves and cam. (Then there's the reliability issue with the rest of the drivetrain. More power, less safety margin)

Speaking of the reliability issue, when I had 45DCOEs on my B20 Volvo Amazon, I managed to break the differential, propeller shaft and gearbox - ALL AT THE SAME TIME!! But the carbs always worked fine. I'm back to a single Stromberg on that car now for inspection purposes.

Dialing in the Webers was easy enough, just very time consuming. I've also done the same on a 2.0 Ford Sierra. I don't have a kit of jets, just a set of number drills 61-80 and a portable CO meter. If I would drill too big, solder fills up the jet and I would re-drill. Testing under load was the biggest challenge without having a rolling dyno.

I've managed to keep the gas mileage reasonable, but it is to be expected - when you produce more power, you use more fuel.

Lastly, SUs are wonderful carbs not to be under estimated.
 
wow You broke stuff on a Volvo Amazon, I had a P1800 and every thing seemed to be over engineered, never broke anything, even had an OD unit that saw 100k miles with no problems

and by the way at the time I put webers on my TR6 it seemed to be the only option, plus that early TR minifold is a terrible set up and flow problems, now put 4 SU on it and I bet is screams. now I see there is a fuel injection setup that bolts to the cannon intake, Hmmm maybe next bonus

Hondo
 
Jerry,

I have stock SU's on my TR-3B, along with a set of headers that flow into a cherry bomb muffler and twin chrome exhaust tips. The performance and sound are fantastic. I haven't had to touch my carbs in more than 7 years. I do drive the car every weekend as long as roads are dry.


Paul
 
racingenglishcars said:
There's a lot to be said here, though I will say Webers will give considerably more power just as a bolt-on. they simply have a larger area of flow (if you use two DCOEs).
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That's actually not true on a TR3A, at least not with 40 DCOEs. Each SU feeds two cylinders, but the two cylinders do NOT flow at the same time! Each engine revolution, one cylinder sucks for only part of the revolution. Then next turn, the other one does. And the stock SUs have 44mm bores, compared to 40mm on the Webers. So with the stock setup, each cylinder "sees" it's own 44mm bore, instead of 40mm with the Webers.

Besides, too big a carb is just as bad as too small. The factory actually got better mid-range performance on the later cars, by making the intake passages smaller.
 
on 40 DCOE the choke is actually smaller than 40mm you can go down to 28 and I think up to 38mm max, and yes a larger choke, you open the throttle, the velocity drops and it stalls, choke it down and you get low end torque with the loss of upper end power go up in choke and it has the opposite effect, there again infinately adjustable

Hondo
 
billspohn said:
Yes, elevation change is where any constant depression carb shines. It doesn't matter a huge amount normally, but if you change elevation 8000 feet, that's going to throw out any fixed jet carb pretty significantly.
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Exactly why I removed the DCOE's from my TR4. The seat of the pants effect is definitely there, so I missed that. I did not have the skill to really dial them in, the gas mileage suffered terribly and the altitude changes were a problem for me. I live at about 3100', my cabin is at 6000', I regularly drive to Yellowstone Park over a pass at almost 11,000'. I've taken the TR on several occasions to Victoria BC and Wisconsin. The SU's work well no matter the elevation.
 
just add an oxygen tank, like the old(er) people carry around, haha!

maybe our cars can apply for medicar

Hondo
 
Decisions I have a 1957 TR3 with SUs H6. I lucked upon a pair of HS6s. I am replacing the pistons and sleeves (see separate thread). My question is which set to put on. I have worked out the linkage problem.
 
Jayplum said:
Decisions I have a 1957 TR3 with SUs H6. I lucked upon a pair of HS6s. I am replacing the pistons and sleeves (see separate thread). My question is which set to put on. I have worked out the linkage problem.
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Will you also need to change the manifold to accommodate the HS^s?
 
I use the HS6 carbs on my cars (3). Compared to the H6 they are simple to rebuild and do not have the complicated internals of the H6 or the grommets under the float bowls that tend to leak. The big problem until recently was the linkage availability. As the HS6 is shorter you may have more choices for intake manifold and air cleaners.
I found the TR3 to have less room for the carbs and air cleaners than a TR4.
Charley
 
Getting close to a Beta tests on my 3. Engine went together well except for one cranky copper Figure Eight. It got tangled in #1 installation; had to pull #2 out and replace forward figure eight with a spare steel I had from a kit I had. Although the HS6 carbs had been done some time ago, I still tore the down and cleaned them and polished what I could. Now to adapt a TR3 linkage to the TR4a carbs. I believe I have it worked out with some things left to trial and error. I have several new pieces of linkage and a new choke cable. NOW just to design what is needed.
I know the 4a has a cable which comes in high between the carb; I think I can come in low with the TR3 accelerator petal and adapt to this car.
I am using the 4a long intake and it fits fine, I believe even the air filter will fit. These are N/A but I found a source for used ones.
 
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Jay,
I just recently learned thanks to Albert at TRF that the GT6 choke cable is long enough ( plus some) to work on the HS6 carbs when used on the TR3 and 4. It gives you the added feature of having two cables , one to each carb, as intended for those carbs. It makes using the choke so much easier. I had to cutoff some on each cable.
One more item you are going to encounter is the heater hose from the top of the head to the outlet/inlet on the firewall. I had to take use additional hose and form a U shape underneath the rear float bowl and back up to the inlet/outlet.
I finally started the engine for the first time a couple of weeks ago. All seems to be going great after a few items that cropped up in the process.
Charley
 
charleyf said:
Jay,
I just recently learned thanks to Albert at TRF that the GT6 choke cable is long enough ( plus some) to work on the HS6 carbs when used on the TR3 and 4. It gives you the added feature of having two cables , one to each carb, as intended for those carbs. It makes using the choke so much easier. I had to cutoff some on each cable.
One more item you are going to encounter is the heater hose from the top of the head to the outlet/inlet on the firewall. I had to take use additional hose and form a U shape underneath the rear float bowl and back up to the inlet/outlet.
I finally started the engine for the first time a couple of weeks ago. All seems to be going great after a few items that cropped up in the process.
Charley
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Thanks, Charley. I I have discovered the same issue with the water. I was contemplating. PVC elbow or w silt rubber tube.
I already got a TR3 chill cable. I will check and reorder if needed.
 
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