• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

TVR 2500M Triple Weber 40 DCOEs

MatthewsTVR

Freshman Member
Offline
I have a question for the TVR/Triumph guys out there. I own a 1974 TVR 2500m and it has three weber 40 DCOE carburetors on it. These carbs look great, but the problem is that there is a stumble in the acceleration of the car. I have to take off very slow until the RPMs are higher in range. It is sort of manageable if I toggle the choke while driving...It definatly feels like a lean out situation (not enough gas or too much air). The problem never really goes away though.

I have made sure that all of the jets in the carbs are clean and I recently put a fuel regulator on the car which helped a little.

Has anyone else experienced this problem? I need help with this aggrevating problem, I can't find the solution!

Any help or suggestions would be great!

Thank You in Advance,

Matthew
 

ralph_s

Jedi Trainee
Offline
Can't answer your question, but am envious of the triple webers!!
Two years ago, attended Jonh Twist's MGengineering 3 day seminar and spent some time w/ Carl Heideman @ Eclectic Motor works. They've done several triple carb convesions and I'm sure they can help w/ your problem. I'd recommend you email Eclectic Motor Works. They are really good people.
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
They'll ask what comes after the "40 DCOE" first, then you will learn about "progression ports" under the brass caps just outboard of the idle screws.
 

Rocky_LC

Jedi Hopeful
Country flag
Offline
I know this is an old thread, but…..

I just rev up the engine and slip the clutch a little more! It makes for a more exciting drive!
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Since the thread has been risen from the BCF dust, another "stumble" on acceleration may be due to the choke tubes being too large an I.D. Drop those down to the next smaller size and see what happens. Pierce Manifold or Summit should be of help supplying the smaller chokes.
 

Rocky_LC

Jedi Hopeful
Country flag
Offline
I read about that as a possible option…. That might be something that I experiment with. It’s likely that my problem with my minor acceleration stumble is much less serious than the original poster’s was.

My issue is just a minor inconvenience, but I would like to get a little more experience working with these carburetors.

Thanks -

Rocky
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Rocky, if your stumble is from the off, not somewhere after 1,500 ~ 2.5K RPM, check to insure ALL the accelerator jets are squirting properly. With the carbs off the engine, gas in the float bowls, with a full throttle application you should be able to put someone's eyes out at ten feet or so... ;)
 
Last edited:

Rocky_LC

Jedi Hopeful
Country flag
Offline
Thanks for the advice…. I’m not at my car for a while, but I’ll give it a try when I get home!

I have a Weber manual that will also help with figure these carbs out!

Generally, my car runs pretty good, so I’m a little afraid to touch the carbs! They look pretty complicated!

I have had the whole manifold & carbs off for cleaning…..

F047D519-49C7-46FE-90B9-5A63A54C9BC9.jpeg
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Those are the Spanish version, produced after emissions standards were enacted. Bit more fiddly but the principles are the same.

The cover on the #3 accelerator jet looks a bit crusty! Is its O-ring perhaps leaking?

...and I don't see the choke cable on that carb.
 

Grantura_MKI

Darth Vader
Gold
Silver
Country flag
Offline
Wow. Those need a good cleaning IMHO. Would move the petrol hose for easier access to the tubes.
may not need the choke, just a pump and hit the key?
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Wow. Those need a good cleaning IMHO. Would move the petrol hose for easier access to the tubes.
may not need the choke, just a pump and hit the key?
Been my experience as well. In all but really cold weather there should be no need for the choke, just pump once and start it up.
 

Rocky_LC

Jedi Hopeful
Country flag
Offline
I agree on the choke comments…. I live in Arizona, and the car starts easily with no choke after just one throttle pump…

Since it’s a TVR Vixen 2500 that had two SUs originally, only the back two (of three) Webers have the choke hooked up, but that has never been a requirement to get the car started..

My picture isn’t the best, and may be before I cleaned up the carbs, but I only cleaned the outside of them…. I’m too scared to take them apart - the car runs well as it is…

Better pictures to follow!

Rocky
 

Tybalt

Jedi Warrior
Country flag
Offline
Since the thread has been risen from the BCF dust, another "stumble" on acceleration may be due to the choke tubes being too large an I.D. Drop those down to the next smaller size and see what happens. Pierce Manifold or Summit should be of help supplying the smaller chokes.
I'm with the good Dr on this. The later 40 DCOE units (40 DCOE 18 IIRC) fitted to the TR6 conversion kits have a 30mm venturi as opposed to the 28mm venturi fitted to the earlier kits that used the 40 DCOE 2 (IIRC). When I was going through the set up calculations I kept coming up with the primary veturis being 27mm or 28mm depending on exactly what RPM I used for the maximum horsepower point. It was relatively easy to find 28mm venturis, difficult to find 27mm but, hey were made so there are some out there somewhere. Odds are unless you are running the early TR6 US spec camshaft, the 28mm is probably the better choice. The venturi size would be the the first place I would look if those are anything other than the 40 DCOE 2.

TRF used to offer the John Passini book on Webers, I don't know if it is still available from them or not. Brooklands out of the UK did a reissue of the Passini book about a dozen years ago, but again don't know about availability. Plus there is the Haynes Weber book and a Pat Braden book on Webers that go through the various circuits in these carburettors as well as graphs and general calculation information for the various jets as a function of venturi size.
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
There was a lot of the "just bolt 'em on and go" with 40 & 45 DCOE so-called "kits" in the past. We've had to go thru some and re-jet from the supposed "right setup" out of the box more than once...
Brooklands out of the UK did a reissue of the Passini book about a dozen years ago, but again don't know about availability.

The Passini book is about the best, IMHO. And there was a "Part 2" as I recall. I can't seem to put my hands on them at the moment though.

The Haynes one would be my last choice.

Rocky: The sizes are in raised numbers on the inside lip of the tube, not difficult to pull out from the front of the carbs while still on the engine if you want to check the size. The venturi and choke tubes are "indexed" in a slot in the carb body, so you can't get them back in the wrong position. It's worth a look! (y)
 
Last edited:

Rocky_LC

Jedi Hopeful
Country flag
Offline
Thanks for all your suggestions. I had heard about the 30 mm, and 28 mm Chokes (actually Venturi), But hadn’t gotten to the point where I was ready to start messing around with them. It would be definitely good idea to know what exactly is inside my carburetors.

The system was installed by the previous owner. I have a receipt that shows he spent about 40 hours on a dyno tuning it.
 

Tybalt

Jedi Warrior
Country flag
Offline
The Passini book is about the best, IMHO. And there was a "Part 2" as I recall. I can't seem to put my hands on them at the moment though.
The Passini book from TRF was Part 1 and Part 2 combined into one book. The Passini book I have was purchased from TRF and is effectively the combined reissue of Weber Carburettors 1: Theory and Weber Carburettors 2: Tuning and Maintenance from Motor Racing Publications Limited with a 1992 copyright date. It looks like the Passini books are on Amazon, 1 & 2 in paperback at reasonable prices but the hardcover Passini book that I have was shockingly high with used prices ranging from just shy of $300 to $550. On another used book site I saw one for over $750, yikes!

Amazon also has the Brooklands Weber book in paperback at a much more reasonable price range for both new and used ones. It does not list Passini on the cover but if look at the preview, it is identified as the Passini combined book.

The Pat Braden book looks to be readily available. One I forgot about earlier is the Veloce Publishing SpeedPro series book from Des Hamill on Weber DCOE and Dellorto DHLA. Des Hamill had done a bunch of stuff regarding BMC and Triumph engines as well but I don't think any of the Triumph stuff is readily available anymore.

I concur that the Haynes book is the weakest of the bunch but if that is all you can get your hands on, it's better than having nothing.
 

DrEntropy

Great Pumpkin
Platinum
Country flag
Offline
Rocky: Any progress on this?
 

billspohn

Jedi Knight
Country flag
Offline
I like Webers when they are set right - do a great job and never go out of tune (if you leave them alone) but getting them perfectly tuned can be a real bear.

I hate seeing TR6s with those horrid downdraft Webers, so at least the OP opted for the right Weber model.

Not sure why I haven't seen more set ups like this (on my MGC, but triple 1 1/2" or 1 3/4" would work well on the TR6 engine).

mgc2.jpg
 
Similar threads
Thread starter Title Forum Replies Date
bravenrace WTB - TVR 2500M TVR 0
O TVR 2500m weatherstrip source needed TVR 2
Z Just Restored 1973 TVR 2500M, Barn Find TVR 25
T Tvr 2500m For Sale, Nice Original Solid Example. TVR 1
Jastx TVR 2500M tires - what are you running TVR 7
M TVR 2500M Model TVR 4
J TVR 2500M Shop Manual TVR 9
D TVR 2500M Parts Car.......For Sale Other British Cars 6
Slider748 TVR 2500M vs TR6 Other British Cars 6
D TVR 2500M wheel question? Other British Cars 3
R For Sale Nice TVR 280i For Sale Other British Classifieds 2
P TVR Big Valve 4.3 TVR 0
T I added another TVR to the fleet. TVR 10
R Old History - List of USA TVR Authorized Dealers TVR 10
J 1985 TVR 280i Speedometer Cable TVR 4
JoeO 72 TVR Vixen hybrid restoration TVR 1
JoeO 71 TVR Vixen V8 Conversion TVR 26
Grantura_MKI TVR owners. TVR 3
M 1963 TVR Grantura TVR 6
2 1972 TVR Vixen 2500 Radiator TVR 6
Grantura_MKI New TVR TVR 2
arcom For Sale TVR T-Slot 14" Rim and Tire Other British Classifieds 0
JPSmit TVR Typhon Spotted 0
V TVRCC National Drive your TVR Day UK TVR 1
V Le Mans Classic 2016 Early TVR Road trip Adventure TVR 6
Mickey Richaud TR2, TVR Chimaera, MGB... Spotted 8
V TVR Vixen S2 New Pictures TVR 1
V TVR Tuscan Restoration TVR 8
V Changes in TVR Parts Supply TVR 1
V TVR Tuscan headlining Bows TVR 3
V Nice looking TVR Vixen S2 For sale TVR 1
J TVR engine advice please TVR 7
I TVR shop manual TVR 7
glemon Great Wheeler Dealers tonight, Lamborghini and TVR Other Cars 1
T TVR Vixen TVR 3
B TVR with Essex V-6 engine question TVR 5
Z TVR Tuscan Spin Mid Ohio 2012 Racing 0
Marvin Gruber TVR Value TVR 1
T 1972 tvr 2500 TVR 3
aeronca65t TVR EBay-MD TVR 2
Z Mid Ohio TVR / Watkins Glen GT40 Racing 15
aeronca65t TVR for sale TVR 0
aeronca65t Turkey Bowl-TVR TVR 12
Tullamore Rearended in TVR Vixen TVR 16
aeronca65t Another TVR-NH TVR 1
C Very nice Triumph-Powered TVR 2200 Special Racing 9
R Great Showing of TVR's TVR 4
Jastx Greetings from new TVR owner TVR 7
G Early TVR's@ Amelia Island Concours TVR 2
JPSmit TVR Tasmin Spotted 0

Similar threads

Top