I've just rebuilt my DHLA 45.
34 choke, 160 main jet, 180 air corrector, 50 pump jet, 55 idle jet, 7772.6 emulsion tubes

Its a 1340 with ported Redline 12-3005 manifold and 12G1316 ported head.

Vizard recommended 45 idle jets and 45 pump jets, but the car wouldn't even run until I put the 50 pump jet and 55 idle jet in.

The car has heaps more power now, but if I punch it off idle, it cuts out badly before the power comes back on again. Once going, there are no flat spots, just on initial acceleration.

Should I be looking to go bigger on idle jets, pump jets or emulsion tubes?

Cheers

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One reason webbers are used over dellortos on minis is because of flat spots caused buy the accle pump on the bottom of the carbrettor getting too hot from the exhaust and causing fuel to vapour only found that out yesterday from a good source.Also is is the accle pump lever adjusted enoungh to pump a good supply of fuel

Cheers
Mason

If you are converting from SUs to a sidedraught one thing to remember is that with a sidedraught carb (be it a DCOE or a DHLA) the throttle action is much me progressive. You cant just punch it in at low revs and expect the engine to respond like an SU, as you will inevitably flood the carb. Add a performance cam to this mix and the power "cuts out badly" as you said. The many cars here that run an RE13 cam with a sidedraught carb will not produce much power below 2.5-3k rpm. Press the trottle progressively and the carb will produce excellent power.

Oh and re: the statement that Dellortos suffer from fuel boiling from exhaust heat - again many people here run DHLAs w/o any issues. just touch the accel pump of you carb after a run and it'll be no hotter than the rest of the carb body. You can fit a simple alloy heat shield (like the SUs had) if you are still concerned.

I found that the same thing happened on my 998 when I first went over to them. With the Dellortos, the trick is to try a setup, write it down and then go for a drive. Then it is trial and error with the pumps and the Idles - change the idles first and then go for a drive, if that doesnt work go back to the originals and then change the pump jets and so on. Its a bit fiddly but I eventually squared up the balance after a few hours of trial and error.

Webers are good however they dont have the jetting range of the dellortos. However the dellorto stuff is hard to come by nowdays and a lot of the tuners have the micro files and "make their own" type of thing. The weber stuff is plentiful and the setups aim at a band of operation and are a better all round setup if you just throw it on and get it within a ballpark then let the dyno tuner have his way with it(tried both and I prefer the Dell as I have a lot of the jetting for them).

The emulsion tubes are not numbered in a sequential order so a larger number doesnt necessarily mean a larger emulsion tube. The book says 3 tubes(7772.5 - 850/998, 6 - 1275 and up and 7 - 998/1100)are good for the minis and the chokes make a sizeable difference to the setup too. According to Des Hammill(Tuning Webers and Dellortos )the choke size should be 35 or 36mm(yes they do come in odd numbers)but then you would also be remaining with the idle and main jet setup as you have. The 1340 would probably benefit remaining with the 7772.6 emulsion tubes and maybe go to 190 air correctors.

As I said it is all trial and error with these as each setup and engine is unique. I run a completely different setup than that of vizards and the dyno guy said I had it pretty well spot on. The pump lever shouldnt be touched if at all possible as it is set and usually glued there.

Check while you have you noggin under the bonnet and move the throttle and see how much range of movement there is - the pump arm should move immediately when you move the spindle - this gives you your "pump " of fuel as the carb comes up to its progression phase. If it moves a little after the spindle is moved, then you may be starving the engine during that transition phase before the carb comes up on the progression phase.

It shoots petrol clean across my garage when I tested mine - but if you are getting an intermittent spurt, check the diaphragm or adjust the arm itself

Have a play with it though - I knew nothing about them until I bought Makkas Dell and stripped the thing...I played with it for a while and familiarised myself with it - good fun but the Ex hated me smelling like petrol all the time. Have fun.

BTW - I disagree with the heat thing completely - I have the opposite where the carb actually ices up on me. If i leave Canberra I get to the second exit to Goulburn(3 times in a row this happened!!)and the car splutters and misses. I pull over, pop the bonnet and look at the white lump that was the dellorto. 5 mins of heat soaking and all is well again and I have no problems all the way to sydney and beyond - must be the southern highlands thing happening...lol. I have runn the Dell for 3 years and never had a heat issue - more a COLD issue(bastards of things!!!)

Hooroo

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Rob Forsyth
Miniot!!

Craig,
I have had a 1310 with a 45DHLA on a redline 3005, when I got it, it had 34 chokes.
Back then I ran 50 idle jets,50 pump jets, 155 main jets, 170 air correctors, 7772.6 emulsion tubes.
Unlike a Weber, you can easily vary the pump stroke on a Dellorto.
UNSCREWING the 2 nuts INCREASES the pump stroke.
If carb was never set up on a Mini, pump stroke may be too short unless nuts adjusted out.

BTW I found 34 chokes too small after I ported the Redline, it went way better with 36s in, settings as above but 160 main jets and 180 air correctors.

I've run a Dellorto for 13 years, never had this `flat spot due to heat' problem. With a variety of LCBs, currently a Maniflow one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Hi, I agree with Kev check the pump stroke & is petrol actually coming out of the nozzles
I have got a 45 DHLA with 3 1/2" manifold on a 1330
It has got 55 idles, 45 pump, no flat spot

One problem i have noticed is that on RH corners the fuel surges & it stumbles/misses until the corner straightens out.
I will be playing with the fuel regulator pressure to try & solve this

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1275

Here goes again...

Thanks for all the replies. Heat is not the issue because the flat spot is new since the rebuild, new manifold, jets, etc. I was running a gooseneck before, so the whole thing was choked off from air.

I think you may have something with the pump stroke. This is something I haven't been able to find much out about on the web, or in Hammill's book. It looks like the pump is driven by the pressure against the spring which is controlled by tightening or loosening the nuts, not direct linkage to it. The nuts on mine are silver soldered to the rod, so I'm going to have to break out the torch and wick up the solder. Loctite will be going back on after I've adjusted it up.

By the way, my idle adjustment screws are out about 8 to 9 turns, so that means my idle jets are still too small right?

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Yepp - 8-9 is a wee bit too far - I have mine out just 2 and a half on both. Try the jetting mixing and see what you come up with.

Hooroo

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Rob Forsyth
Miniot!!

As someone has said earlier, you can't floor a weber too low in the rev range, it needs to be progressively "stomped" when it is off the cam.

For example in my car 1330 running a Dellorto and RE13, I can't stomp on the pedal between idle and about 2300rpm. it results in a gurgle and that's about it. Above 2300rpm or more it's fine. Hope that's not what you are talking about.

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Lillee - 1969 Morris Mini K

I have found that adjusting the F value as well as size for idle jets on webers corrects this flaw. I went from a 50F2 idle jet to a 45F9 (I think anyway, 10 years ago!). The idle jet size (ie 45/50) is the hole size and the F value is the air correction. As with the main circuit, the air correction has more effect at higher air flows so changing this will affect progression more than idle which is adjusted by the screw.

I would adjust the idle mixture screws to see if you can correct the stutter. Start from say 1/2 turn richer and see if it wants this or weaker setting than idle and change jet accordingly.

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

When I bored the 1310 to 1360 and fitted 38 chokes I found the 50 idle jets too small, so I now run 55s.
If you have yours so many turns open, I'd say it wants bigger idle jets.
Dellorto jets go up in 1s, so you can get 51, 52, 53 etc.
Remember the idle jets work (via the progression holes) up to about 1/8 throttle, and this is where flat spots often happen. As said, do check both pump jets are spraying- but usually if not, the engine will `sneeze' when you open the throttle.
Best way to check this is on the bench- open the throttle (with fuel in bowl) and both jets should spray well past the throttle plates.

I recommend Des Hammill's book `How to build and power tune Weber and Dellorto carburettors' it's cheap, and a wealth of information.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Good info here. I'm starting as I said by adjusting up the pump stroke (if it's too short), and then in the following order replacing:
1. 180 air correctors with 190
2. 50 pump jets with 53 pump jets
3. 55 idle jets with 60.

As mentioned with examples by Kevin and others, I shouldn't need to increase any of the above based on what my Dellorto is set to now. In other words, it should be big enough. Still, the number of turns on my adjustment screws has me confused. It started running really smoothly at about 8 turns, and before that had a slight stumble. I blew out the idle screw holes in the carb body with carb cleaner just to make sure they were clear, and put copper grease on the screw threads to make sure they were seating all the way down to start. Increasing the stroke of the pump shouldn't have anything to do with the 9 turns out of the screw. It would be idle jets, and I'm already running 55 idles.

The other thing to say is that I really stomped it all the way to the floor from idle when it cut out. I'd never drive this way regularly, and ever since I've had this Dellorto it cuts when I stomp it. As mentioned, they need to be feathered until around 2.5k, then they really take off.

Edit: Checked the pump stroke tonight and the pump lever moves the instant the throttle is activated, and it reaches it's full stroke. I'll probably try the 3 things above, and get the 36mm chokes sometime in the future and call it good.

For those who say they get no cut out or stumble, does that mean you can floor it from a dead stop and the motor just revs up smoothly through the power band? This is the situation where I get the cut out. If I ease into it and get past 2000 rpm before full throttle, then it takes off with no hesitation. Many people say that Dellortos have to be eased into, so maybe my carb is going good.

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Disclaimer - I'm not 100% on dellortos but my knowledge of webers is pretty good so you'll have to figure out if what I say makes sense...

The air corrector on the end of the main jet emulsion tube is for wide open throttle, high speed use. It won't really change anything at low air consumption, going bigger will result in high engine speed detonation/lean out - the worst kind (one you can't hear) if you are not careful.



it may be a dellorto thing but as I said above I could bang the throttle open from low engine speed with no hesitation from changing the idle jetting.

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

As Doz says, the air corrector jet affects the top end only. This applies to Dellorto as well as Weber.
Most Dellortos I've set up on road cars seem to prefer a 180 air corrector.

If taking Dellortos off an Alfa for a Mini, you can bin their emulsion tubes. They will NOT work, too many holes in `em.
I find either a 7772.5 or a 7772.6 is the biz.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Well I took it out for a good flogging last night and after it warmed up for about 10 minutes of driving, the stumble on acceleration was gone. Interesting though in that even when the temp gauge got up to where it normally sits after a few minutes of warming up, the car cut out/ stumbled on hard acceleration. After 10 minutes on the road though, I could stomp it at idle and it picked right up.

Still, the 9 turns out of the screw tells me that I need to give my idle jets some attention. I've ordered size 60 idle jets and size 53 pump jets and will play with that. Hopefully I can get the screws down to 2 or 3 turns out.

All in all its running better than ever. A little fine tuning, and 36mm chokes once I find some will get it right where I want it.

Craig

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