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I know this has been posted before, probably numerous times, but here is what seems to be a pretty definitive guide on Webers for TR3s and 4s:

http://www.tr3a.info/WeberDCOEinfo.htm (this is the "TerriAnn" guide)

She is basically saying that for fast road use-case the 'best' choke size is going to be 34 which is the one option common to both 40DCOE (for best overall power curve up to 5000rpm) and 45s (if you need to run higher revs eg racing).

Or 42s if you happen to find a pair, they were used on the Works TR4s although given the rarity I guess may not be worth searching for unless you're trying to create the ultimate 'tribute mobile'.

(If any of this sounds like I know what I'm talking about by the way, beware. :) )

Stuart: which Dellortos did you go for? 

Nigel

Edited by Bleednipple
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3 hours ago, Bleednipple said:

I know this has been posted before, probably numerous times, but here is what seems to be a pretty definitive guide on Webers for TR3s and 4s:

http://www.tr3a.info/WeberDCOEinfo.htm (this is the "TerriAnn" guide)

She is basically saying that for fast road use-case the 'best' choke size is going to be 34 which is the one option common to both 40DCOE (for best overall power curve up to 5000rpm) and 45s (if you need to run higher revs eg racing).

Or 42s if you happen to find a pair, they were used on the Works TR4s although given the rarity I guess may not be worth searching for unless you're trying to create the ultimate 'tribute mobile'.

(If any of this sounds like I know what I'm talking about by the way, beware. :) )

Stuart: which Dellortos did you go for? 

Nigel

Ive got DHLA40 they were originally on a 2.1 Pinto but theyve been seriously re-jetted and with larger chokes since, I have a wide band sensor plus a gauge in the car so I can keep a good eye on how it runs.

Stuart.

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2 hours ago, stuart said:

Ive got DHLA40 they were originally on a 2.1 Pinto but theyve been seriously re-jetted and with larger chokes since, I have a wide band sensor plus a gauge in the car so I can keep a good eye on how it runs.

Stuart.

+1 for the Dellortos.

The story goes the Weber came out first and all the "why didn't they do that" and "this is a pain" problems were learned from and the Dellortos engineered to be better. The Webers carry the mystique but the Dellortos are better value and if you scan e bay you'll readily find them at much lower prices than the Webers. From the Lotus Elan club writings these observations.

 

...Once set up, there's probably little difference between the performance potential of Weber DCOE and Dellorto DHLA carbs; however, they're not simply different flavors of the same taffy. There are differences between them, and for my money, I prefer Dellortos. I'm not trying to start a debate. If you like Webers, use them.

Dellorto calibration parts, like jets and mixture screws, offer much finer resolution. Weber Main Jets are available in size steps of five (130, 135, 140...) while Dellorto's are available in steps of one (131, 132, 133, 134...). Same with Idle Jets, Accelerator Pump Jets, etc...

The Weber Idle Mixture Screws have blunt tapers and coarse threads, while Dellorto's have long slender needles and fine threads. Then later, the "E" models (40E & 45E) got even longer tapered needles and finer threads. Weber mixture screws usually end up adjusted about 1 1/4 - 2 1/4 turns out, while Dellorto screws end up 2 3/4 - 3 3/4 turns out.

Overall, it's much easier to sneak up on a very exact mixture setting with Dellortos, while you just sort of take big steps with Webers.

The Weber progression circuit often has only 2 or 3 holes, while Dellortos have 5 or 6. The Dellorto 6-hole progression is a Lotus development for their own models which Dellorto later adopted across it's own main product line.

The 6-hole setup gives the Dellorto a much smoother progression off-idle so the carbs depend less upon a heavy shot from the accelerator pump. The Weber, on the other hand, uses a big pump shot. So much so that Weber carbed engines often deliver significantly shorter piston ring life compared to their Dellorto/ Stromberg counterparts due to the Weber pump shot washing down the cylinder walls all the time.

The Weber accelerator pump's piston runs in a bore machined into the body. It's metal to metal, is subject to "blow-by" do to clearances, tends to wear over time, and the bore can't be repaired. On the other hand, the Dellorto diaphragm pump has no blow-by and clearances don't wear with use. Then when it does get old, the pump is easily rebuildable back to 100% spec by simply replacing the diaphragm and gasket.

Weber's are more prone to leak. I'm not saying that they all leak, just that they're more prone to leak. I have three Lotus engines with pairs of DHLAs, and they "never" leak, and they don't smell of gas any more than is typical of a normal carb (ie, vented float bowls). The Webers in the other car are always having leak issues and the car wreaks of gas.

Someone I know at Lotus Cars once told me switching to Dellortos was Lotus' answer for solving persistent fuel leak issues.

 

...So individual preferences for both makes of carb exist and are championed by their users, your money your choice.
 

Mick Richards

Edited by Motorsport Mickey
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On 2/21/2021 at 8:01 AM, North London Mike said:

 

. You can cruise, keeping the second choke closed but its counter intuitive. The price is about 5mpg

20200806_152006_resized.jpg

That would be some trick, to keep one choke closed as they're on the same shaft ^_^

The idle circuit handles cruising up to ~3000 rpm. So 70mph with O/D. One step in size of this jet can affect fuel economy as much as 20%.

Tom

 

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21 hours ago, Bleednipple said:

I have SUs on my TR4 and will probably keep them, but while there are some Weber experts on here... I have a pair of 40DCOEs on another car I recently acquired (an Alfa). They have no cold start circuits fitted I think (certainly have no actuation cables), so are a minor pain to start - I have to resort a quick spray of Easy Start when cold. I'm not going to fiddle with them myself but can anyone explain in simple terms the cold start gadgetry on sidedraught Webers?

(Or maybe I'm just using a poor starting technique!)

Nigel

I've always employed cold starts on my Webered '250s, maybe because they're " there ". Like Neil says, push in once they fire and keep at 1500 rpm for a few secs or more if quite cold. TR4 choke cable, sections of sheath fitted between carbs to armor the strand.

The cold start on DCOEs is a separate circuit with its own jets and air intake through a superfine brass screen facing below. They have a distinctive sound when open.

 

 

Tom

TR PCV AND SILENCER SHOTS 009.jpg

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8 minutes ago, Tom Fremont said:

That would be some trick, to keep one choke closed as they're on the same shaft ^_^

The idle circuit handles cruising up to ~3000 rpm. So 70mph with O/D. One step in size of this jet can affect fuel economy as much as 20%.

Tom

 

Sorry Tom. Technical error :wacko: Lets settle for light throttle opening ;)

Ps. No cold start, garaged when cold, never been a problem but appreciate cold start could be an issue, especially if not properly set up

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1 hour ago, Motorsport Mickey said:

From the Lotus Elan club writings these observations.

 

.
The Weber progression circuit often has only 2 or 3 holes, while Dellortos have 5 or 6. The Dellorto 6-hole progression is a Lotus development for their own models which Dellorto later adopted across it's own main product line.

The 6-hole setup gives the Dellorto a much smoother progression off-idle so the carbs depend less upon a heavy shot from the accelerator pump. The Weber, on the other hand, uses a big pump shot. So much so that Weber carbed engines often deliver significantly shorter piston ring life compared to their Dellorto/ Stromberg counterparts due to the Weber pump shot washing down the cylinder walls all the time.

The Weber accelerator pump's piston runs in a bore machined into the body. It's metal to metal, is subject to "blow-by" do to clearances, tends to wear over time, and the bore can't be repaired. On the other hand, the Dellorto diaphragm pump has no blow-by and clearances don't wear with use. Then when it does get old, the pump is easily rebuildable back to 100% spec by simply replacing the diaphragm and gasket.
 

Progression holes are the " black box " of these carbs and messing about will ruin them; the nightmare scenario of buying used is to get some that have been tampered with ( I never have, fortunately ). Adding holes would have to affect the jet and emulsion tube sizes dramatically - essentially starting from square one on the calibration exercise.

 

The Weber pumps can be tailored to a gnat's eyebrow with the various strokes, sizes and bypass orifices available. This is the first claim I've come across that Weber accel pumps wear out piston rings. I guess I've been lucky on my driver's ( brass throttle shafts, truly ancient ) which have preserved the rings so far with 135,000 miles under their belt and 3000-4000 miles per US quart of oil with no valve guide seals AND an auxiliary rocker oil feed line. I'll have to peek at the bores of the pump wells but if they're worn they exhibit no symptoms at all.

Weber came out with the DCOM which I think has diaphragm pumps. No one wants them; they languish on ebay. 

Being Italian, I am sure Dell'Ortos ( " from the garden " ) are well made. They should be better as they had to beat an icon at their own game; if they succeeded it would be by token amounts IMO  ( e.g.  the 1/100 mm increments in jet sizes which seems more of a symbolic effort to trump the original ). Weber owns the cachet, and with all our beloved TRs in the antique category I daresay they will always fetch more - which is why for performance purposes the Dellortos may be a bargain.

My Webers leak a tiny bit and reek of fuel indeed. I would love to come up with a nice airbox I could cap off between runs to address it, a real challenge due to the early wheel arch notch.

 

Tom

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It is important to consider the decision to fit Webers or Dellortos in the context of an overall performance upgrade. The bottom end, cam and head work may all be influenced by whether or not the you are intending to stick with SU's or Weberise. To get the best out of Webers or Dellortos you probably have to be willing to explore the North end of the rev range and some cams work better with SUs and some work better with Webers.

Slapping the wrong carbs on the wrong set up may lead to disappointment.

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  • 5 months later...
On 2/22/2021 at 8:05 PM, Tom Fremont said:

Progression holes are the " black box " of these carbs and messing about will ruin them; the nightmare scenario of buying used is to get some that have been tampered with ( I never have, fortunately ). Adding holes would have to affect the jet and emulsion tube sizes dramatically - essentially starting from square one on the calibration exercise.

 

The Weber pumps can be tailored to a gnat's eyebrow with the various strokes, sizes and bypass orifices available. This is the first claim I've come across that Weber accel pumps wear out piston rings. I guess I've been lucky on my driver's ( brass throttle shafts, truly ancient ) which have preserved the rings so far with 135,000 miles under their belt and 3000-4000 miles per US quart of oil with no valve guide seals AND an auxiliary rocker oil feed line. I'll have to peek at the bores of the pump wells but if they're worn they exhibit no symptoms at all.

Weber came out with the DCOM which I think has diaphragm pumps. No one wants them; they languish on ebay. 

Being Italian, I am sure Dell'Ortos ( " from the garden " ) are well made. They should be better as they had to beat an icon at their own game; if they succeeded it would be by token amounts IMO  ( e.g.  the 1/100 mm increments in jet sizes which seems more of a symbolic effort to trump the original ). Weber owns the cachet, and with all our beloved TRs in the antique category I daresay they will always fetch more - which is why for performance purposes the Dellortos may be a bargain.

My Webers leak a tiny bit and reek of fuel indeed. I would love to come up with a nice airbox I could cap off between runs to address it, a real challenge due to the early wheel arch notch.

 

Tom

Edoardo Weber was Italian and before relocating to Spain, the factory was in Bologna (Reggio Emilia) Italy.

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On 2/21/2021 at 9:17 PM, ntc said:

Single fuel and air delivery to each cylinder is more efficient simple 

if you add "at high revs." that statement is correct,

 otherwise David Vizard would argue against that statement. He argues that if you can get a single carb to do the job it is a much more efficient way of getting fuel & air into an engine ;

4cyl engine with 4 carbs = 1 suction event per carb every 2 revolutions of the engine, air flow constantly stopping and starting.

4 cyl engine with twin carbs= 1 suction event per carb every revolution of the engine, air still stopping and starting but pulses closer together.

4 cyl engine with single carb = 2 suction events per revolution of the engine, almost constant flow through the carb.

Hence a single carb is more efficient, but falls short at high revs when increased volumes of air are required.

That`s why  shopping cars have single carbs and sports cars have 2, and racers have 4 or more..

Also the reason why bolting a set of Webers on to your mums Ford Anglia will do nothing other than increase fuel consumption (although it will undoubtedly sound better)

Ralph

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11 minutes ago, Ralph Whitaker said:

if you add "at high revs." that statement is correct,

 otherwise David Vizard would argue against that statement. He argues that if you can get a single carb to do the job it is a much more efficient way of getting fuel & air into an engine ;

4cyl engine with 4 carbs = 1 suction event per carb every 2 revolutions of the engine, air flow constantly stopping and starting.

4 cyl engine with twin carbs= 1 suction event per carb every revolution of the engine, air still stopping and starting but pulses closer together.

4 cyl engine with single carb = 2 suction events per revolution of the engine, almost constant flow through the carb.

Hence a single carb is more efficient, but falls short at high revs when increased volumes of air are required.

That`s why  shopping cars have single carbs and sports cars have 2, and racers have 4 or more..

Also the reason why bolting a set of Webers on to your mums Ford Anglia will do nothing other than increase fuel consumption (although it will undoubtedly sound better)

Ralph

Also why a Frogeye Sprite back in the day would go better on a single 1 1/2" rather than original twin 1 1/4"

Stuart.

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1 minute ago, stuart said:

Also why a Frogeye Sprite back in the day would go better on a single 1 1/2" rather than original twin 1 1/4"

Stuart.

Also why I have a re jetted 1 1/2 on my MG engined, cooper cammed, and gas flowed A35 van. (and it keeps the insurance company happy).

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I thought Frog eyes had twin 1 1/8" carbs.  I fitted just such a pair to my first car a 1098cc Morris 1000.

13: CR, gas flowed & ported head. clocked at 103 MPH !

Bob.

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2 hours ago, Lebro said:

I thought Frog eyes had twin 1 1/8" carbs.  I fitted just such a pair to my first car a 1098cc Morris 1000.

13: CR, gas flowed & ported head. clocked at 103 MPH !

Bob.

+1 All Frog Eyes were 948cc A Series were H1  1 1/8” twin I believe. The later squarer shaped Sprite were 1 1/4” on the 1098cc. One of nicest A Series was the 1071cc but only seen I believe in the earlier Cooper S ‘64 ish for a limited production run. Don’t think the 1071 was fitted to any other BMC/ Leyland model afaik?

Kevin

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