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Dellorto side draft carbs

850 Combat

850 Combat

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Past Site Supporter
I've been running dual Dellorto side drafts on a '68 Ford Cortina, since 1993. Lately, it has begun to exhibit softness in part throttle transitions between idle and mid range. It is worse than a hesitation. I rebuilt them a couple years ago.

Unlike Webers, these have diaphragm type accellerator pumps. Anybody have any ideas?
 
Nice ride...I'm currently considering another car for a daily driver - an MG midget {another midlife crisis/bucket list item}, so it's nice to see the lil cars represented.

My last old car {70 cougar/351C} had a similar issue.....rebuilt the carb when it got here but 2 years later the accelerator pump went bad due to the diaphragm getting ate up from modern gas.....I'd suggest replacing the diaphragms and see how she runs then.
...I'll trade ya troubles...I've got to deal with a carter ball and ball carb on a flathead 6...spare motor is a larger flathead six with twin carter AS carbs on an ellis manifold cause it'll look cooler{lol}....I like to be different!
 
I was suspecting the diaphragms, but the used ones it had when I bought it lasted 20 years without failing. I bought a set from CB Performance products. I switched the car to an electric fuel pump, and I always disconnect it and run it dry prior to parking the car for an extended period. I did reduce the stroke adjustment of the accellertor pumps when I rebuilt them.
 
Gas has gotten more ethanol thru the last few years, and I have no idea what the difference is between the "summer blend" and "off season blend", let alone any of the other additives they throw in.....the conspiracy theory is that they do it on purpose to kill off the old vehicles{chuckle}....leaded to unleaded and so on...
If you reduced the pump stroke, I'd assume it ran fine then...so if it did, I'd figure it wasn't that.
-Did you check all vacuum hoses for cracks or leaks?...that might do it too....
-Fuel pump pressure up to snuff? {gauge to read off of?}...I remember my old GLH turbo - end of 1st year she started running bad. Turned out the fuel pump was bad and a new one fixed it.....just remembered my 25th anny camero had that same issue and fix {well, that car had all sorts of issues...shoulda kept the GLH}.
 
Genuine OE diaphragms could be used with methanol - I've done it. But i have no idea if they're available now.
I'd second the diaphragms - with a strong caveat that all the vacuum hoses get checked too.
That's a long time to run the same setup and hoses do go porous...
 
It doesn't have any vacuum hoses. It has a new re-curved distributor with a Luminition trigger. Mechanical advance only. This problem started a year or so after the after the o;d Alden /Lucas/ Luminition distributor that I had installed 20 years ago.
 
850 Combat said:
It doesn't have any vacuum hoses. It has a new re-curved distributor with a Luminition trigger. Mechanical advance only. This problem started a year or so after the after the o;d Alden /Lucas/ Luminition distributor that I had installed 20 years ago.
Click to expand...

Fair enough. It may need a session on a dyno to redo the advance curve to suit your current gas. I've found that here in NZ where ethanol levels are still low, the big 2V race engines like a lot more agressive advance to fatten up the midrange. In a car, I'd just advance it till it pinks - then back it off a tad...
 
That is that I replaced the old Lucas /Alden mechanical advance distributor with a new re-curved distributor from JAE (One of the larger and best known Lotus parts sellers in the USA) which came with the Luminition pre-installed. The older distributor had the Lumination installed by me. Luminitions are notorious for failing if the ignition is left on without the engine running, which I had done more than a few times over the years, for one stupid reason or another.

The distributor is curved for a modified Lotus twin cam, but the Aldon was curved for a Formula Ford. They both are a pretty quick curve.
 
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It was simple. The air needles were open too far, and it had a lean transition off idle. One of the air needles is slightly bent, and I haven't been able to source a new one. The bend is outside of the carb. The metering part is fine, but it doesn't feel right threading it. Now I'm having trouble with the DCOEs on my Lotus Seven. I think the pilot circuits are clogged. A dip in the carb cleaner made them worse though. Maybe my 5 gallon pail of Berryman's has gone bad. I want to get the 7 running right and sell it. I did use the Cortina as a daily for a couple weeks in Oregon. I didn't take the Esprit out at all.
 
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