Weber vs. Dellorto

[summerinmaine]

I searched but did not find. Is there a thread that covers the differences/advantages between the two?

Not trying to start a DinoWine vs. synthetic type controversy, but I imagine that this comparison has been done before.

Thanks.

[kenny]

Have used them both on numerous applications. Currently running a set of DHLA 45's on a VX 16v and a set of 45 DCOE's on another 16v albeit in a higher state of tune.

In all honesty I could not say one is better than the other especially if both sets are fully serviced,clean and jetted correctly for the given engine.

I've often heard bar room stories about Dellortos "staying in tune" better than Webers but I always maintain these carbs don't go out of tune..............it's the throttle levers that may cause the problem by bending or by the lever adjustment screw not being secured properly and moving thus causing the imbalance between the two.......which is an easy fix.

I guess it comes down to whether you want to see a nice shiny wingnut on top of the body or not

Cheers

Kenny

[summerinmaine]

Thanks Kenny,

I've heard some similar claims about the DHLAs, but have never been sure whether to chalk them up to Weber envy.

[Elanintheforest]

The only difference I've found betwen the two is after they've not been used for a while. I've always been able to get a weber car going quite easily, even after not being run for many months or even years. After the same sort of time, the Dellortos seem to need stripping / rebuilding...everything seems to freeze up quite easily. A mate who rebuilds twincams for a living has the same experience.

Of no interest if you're using the car regularly, but may be an indication of quality / design differences?

Mark

[Esprit2]

The only difference I've found betwen the two is after they've not been used for a while. I've always been able to get a weber car going quite easily, even after not being run for many months or even years. After the same sort of time, the Dellortos seem to need stripping / rebuilding...everything seems to freeze up quite easily. A mate who rebuilds twincams for a living has the same experience.

Mark,

Interesting. I have exactly the opposite experience. My three sets of Dellorto DHLAs combined don't give me the putzy cleaning workload my one Weber DCOE carbed engine does.

Regards,
Tim Engel

[Esprit2]

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.

Regards,
Tim Engel

[summerinmaine]

So, am I right in now thinking that this topic hasn't already been done to death?

If so, then I'm glad to see the experiences of others. Please share what you've got.

[Esprit2]

It's an old topic that was done to death before it started. Just browse the archive.

Regards,
Tim Engel

[summerinmaine]

It's an old topic that was done to death before it started. Just browse the archive.

Regards,
Tim Engel

I suspected it was, but my search of the archive was less than fulfilling.

Perhaps my browse-fu is weak.

[bill308]

summerinmaine,

I think a lot of the differences are model specific. Not all DHLA40's are the same and not all 40DCOE's are the same. Early versions of both the DHLA40 and the 40DCOE were pretty similar feature wise, including 3-progression holes. The DHLA40's are reported to offer better low speed atomization, that is, the ability to effectively vaporize the liquid fuel, especially at low air flows. This promotes better mixture adjustment of the idle and transition circuits where most of my driving occur's. Once on the mains, the carbs are pretty much the same. Classic versions the DHLA40 (no suffix) and 40DCOE18's were tuned to get on-the-mains as soon as possible and do most of your driving in this regime.

Later performance versions of these carbs added some useful features, an idle air balance circuit and up to 6-progression holes (ex. DHLA40C thru E). Added progression holes enabled an extended transition zone so cut in of the mains could be delayed, but when they come in, they should come in with more than adaquate atomization. Full tuneabilty of the idle, progression, and main circuits,were retained by these carbs, unlike some of the later emission versions of the Dellorto.

I like my 40DCOE18's a lot, but while crawling around the neighborhood, there was often a premature misfire under some low flow conditions, like when you're rolling to a stop, in gear, at a congested intersection and maybe you just want to maintain speed a little longer before braking. Perhaps with the use of a portable A/F meter, the mixture could have been better. Maybe this would have overcome this small annoyance. In the end I opted for a nice set of rebuilt DHLA40E's with extra tuning bits.

Bill

[davidj]

Hi,

One of the problems with the Dellorto was the diaphragm pump, which tends to leak over time dripping petrol onto the dizzy and starter. I have heard this was the biggest cause of fires in the Elan. While our cars are pampered and checked on a regular basis the average owner when the cars where new probably never opened the bonnet one month to the next, and the leaks were not noticed.

David

[Esprit2]

David,

Strombergs, Webers and Dellortos each have their own ways of leaking onto the distributor and starter below them. The fire risk wasn't isolated to Dellortos, but common to them all, and had more to do with the relative positions of the electrical bits below the carbs rather than any one of the carb's unique propensity to leak.

While a torn Dellorto accelerator pump diaphragm will result in a leak out of the bottom cover, overall, Dellortos were less prone to leak than Webers. Dellortos were Lotus' solution to the problems they had with Webers.

Any leaking carb would be a fire risk on any Twink (907 as well since the starter and distributor are similarly located), but I believe the greatest fuel leak fire risk was due to the plastic T-connector used between a pair of Strombergs. That was a very bad idea that reduced a number of cars to ashes. I certainly hope no one running Strombergs still has a plastic fuel T installed.

Regards,
Tim Engel