Just Fitted Twin 40 Dellorto

[Guest THE COACH DRIVER]

I have just fitted twin 40 dellorto carbs but is backfiring through the carbs and flames coming out of the exhaust,I have the standard dissy just not conneced the advance pipe iso what do i set the timming to, it is 1.6 pinto running manual fuel pump

any help would be much appreciated

Regards

Mick

[Guest salty_monk]

That's a lot of carb for a 1.6 pinto.... you can run a modded 2.0 off a set of 40's. What jetting do you have in the carbs? Timing shouldn't change from stock unless you have a different advance curve.

 

Dan

[Guest THE COACH DRIVER]

That's a lot of carb for a 1.6 pinto.... you can run a modded 2.0 off a set of 40's. What jetting do you have in the carbs? Timing shouldn't change from stock unless you have a different advance curve.

 

Dan

The carbs came of a 1600 xflow so should be jetted ok, i have turned the dissy always but still popping through the carbs and running rough

Regards

Mick

[Guest salty_monk]

I've seen them run on Xflows before, usually pretty highly tuned 1600's or Vulcan 1700's or similar..... What spec is your engine?

 

If it was running fine before & all you did was change the carb then you know what the problem is......

 

Set the dizzy up with a timing light & leave it alone if I was you...

 

Dan

[Snapperpaul]

Dellorto DHLA Carb set up for standard 1600 Pinto (also recommended for 1800 and 2000)

34mm chokes

140 main jets

7772.10 emulsion tubes

180 air correctors

7850.1 idle jet holder

40 idle jets

7848.1 auxiliary venturis

40 pump jets

float level shut off height - 15mm

float level at full droop - 25mm

 

12 degrees of advance at idle 600 rpm

38 degrees of total mechanical advance at 3600 to 3800 max

[Guest gavinc]

had some fun setting up dellortos on the pinto....

 

hers some info i collected of the net...

 

stolen from other people so please forgive me..

 

Ian,

 

Set-up and tuning Dellortos is about the easiest carb work out there, much more so than webbers.

 

There are basically 4 steps to the process; (1.) check/set float heights (2.) adjust each barrel for optimum performance (3.) balance each carb (4.) balance the pair of carbs.

 

Using a Unisync tool isn't the best way to go about it as the Unisync goes into and affects the very airflow you are trying to adjust.

 

A CO meter isn't really very good either. There are two reasons for this; First, tuning for performance vs CO are usually two different things. Secondly, because the CO meter samples the exhaust, it is sampling the net result of all 4 carb barrels and cylinders. You could have two opposing errors cancel each other out, achieve a proper CO reading and still have lousy running carbs. In other words, you may be adjusting one carb barrel to compensate for the maladjustment of another putting them both out of whack, with the CO meter totally oblivious to it all.

 

The best way to tune Dellortos is by using a 4 column manometer, which I see in your pictures. I used to use an Hg manometer, but several years ago I switched to a mechanical manometer, because it is less inconvenient (smaller) and there's no Hg to worry about. It's made in the UK by Mogan and is called the CarbTune II, an excellent quality tool.

 

First set the float heights according to spec., 14mm I believe. Pull the carb covers, the floats are attached to the underside. Hold the carb top perpendicular to the ground, allowing the float arm to just contact the needle valve, then measure the gap between the top of the float and the underside of the carb cover, make sure to allow for the thickness of the gasket in your measurements. Adjust to the proper gap by gently bending the float arms. Be sure to check the gap on both floats.

 

Once the floats are properly adjusted, secure the carb covers (take care not to disturb the float heights).

 

Start the car and let it come to operating temp.

Then, hook up your manometer to all 4 test ports.

 

Start the car and set the idle at 900 using the idle speed screw to adjust the engine speed.

 

Close (turn clockwise all the way) all 4 air adjustment screws. Take care not to agressively tighten down, you want to avoid 'grouching' these needle screws. Note, there should only be one screw open on each carb, if not, they were previously improperly adjusted.

 

Next, using the idle mixture screws, adjust each barrel on a single carb (doesn't matter which) to produce the highest column on the manometer. In this entire process, the values graduated on the manometer are meaningless, you are seeking the highest column regardless of value. Take care to mind the RPMs during this process and continually adjust them back to 900RPM using the idle speed screw. Do this for all 4 individual carb barrels. All 4 air adjustment screws must remain closed for this process.

 

Once all 4 barrels are set to yield the highest level possible on the manometer, you will synchronize the barrels of each carb to their 'mate'. First, select a carb to balance. Note which of the two barrels produced the highest manometer column. This is the barrel you will adjust. In small increments, open the the air adjustment screw of the strongest barrel until it's column drops to match that of it's 'mate'.

Be sure to give the engine about 5 sec. between each adjustment to allow it to adapt to the new setting.

 

You use the stronger of the two barrels because you can weaken it, but you cannot strengthen the weaker one. Do this for each carb. When done, you will have only 1 air adjustment screw open per carb, and each carb will have two matching columns, although they will most likely not match the columns of the other carb. Again, be mindful to hold engine speed to 900RPMs throughout this entire adjustment.

 

Finally, you are going balance the two carbs to each other. This is done using the carb balance screw on the linkage between the two carbs, engine running at 900 RPMs. Once again, you must weaken the stronger carb to match the weaker one. You turn the balance screw in whatever direction is necessary to drop the column levels on the stronger carb to match the weaker one. Again, allow 5 sec. for the engine to respond, and maintain 900RPM throughout the process. When done, you will have all 4 columns equal.

 

Voila, your're finished!

 

If you still have poor performance and/or idle, things to check are;

 

Clogged Carburettor fuel filters - Dellortos possess a fuel filter (a simple screen filter) attached to the underside of the needle valve seat. If these become clogged or varnished, they will affect carb performance.

 

Leaks in the carb mounting insulators - Check these by holding a propane torch to each intake runner, open the torch valve releasing some propane, if engine revs differ, you have a leak. Replace rubber insulators, do not merely tighten them down as these are set to 'float'. If tightened down, engine vibration will cause foaming of the fuel in the carb bowls.

 

Worn air adjustment or idle mixture screws - Check to see that their 'needle' points are not 'grouched', if so, replace.

 

Clogged jets - Remove the jet access cover on top of the carbs, unscrew the jet tubes and place in a solvent, such as Tolulene a couple minutes to dissolve any varnish and blow dry using compreseed air. You can also buy canned pressurized carb cleaner to do this job.

 

Worn Carbs - The carbs may simply require a rebuild. A broken spring or leaking accelerator diaphram, varnish build-up, or failed gaskets and seals may be to blame.

 

Fuel Pressure Regulator - misadjusted or faulty, this will also affect the carbs performance.

 

Fuel Pump - in the extreme, this may be faulty.

 

Hope this helps. Happy Motoring! ...Jim'85TE

[Guest gavinc]

and another..........

 

 

DELLORTO

 

 

Assuming that the carbs have been rebuilt or are in good shape (emphasis on good), you need a 4-pot manometer to properly tune them. Either an actual Hg manometer, or a manual one such as the CarbTuneII. Make sure the float levels are between 14mm & 14.5mm which is nearly double what a Weber float is set at.

 

Turn all air bleed (or air balance screws) closed and turn down all the mixture screws, taking great care not to grauch the needle screws.

 

Then turn out each mixture screw 3.5 turns (this will be sufficient to start the car). Start the car and let it warm to operating temp., set idle speed screw until car maintains 1000RPM.

 

With the manometer connected to the test port on each barrel, turn each mixture screw while observing the manometer level and the tach. Turn each screw until the idle increases and level in the manometer reaches it's maximum, then turn the screw the opposite way 1/16th to 1/8th turn (allow about 5 sec. between screw adjustments so the new metering can take place). Do this for all 4 mixture screws, all the while using the idle speed screw to maintain 1000RPM. You will now have each barrel set to it's optimum mixture, yet the levels of each barrel will not necessarilty match each other.

 

Next, working on a single carb (doesn't matter which), maintain 1000RPM and observe which of the two barrels reads a higher level than the other (this is the strong barrel). Open the air bleed screw of the stronger barrel until it reaches the level of the weaker one. Do this for both carbs, maintaining 1000RPM. When done, you will have only one air bleed screw per carb open and will have two pairs of equal levels, but not necessarily equal to each other.

 

Finally, using a 7mm wrench, adjust the carb balance screw between the two carbs so that the stronger of the two pairs of manometer levels drops to match the weaker one (the reason being that you can weaken the strong one, but cannot strengthen the weaker one).

 

Assuming that your carbs are in good order, no leaks, leaky soft mounts, clogged filter and proper regulator pressure, your carbs will now be perfectly balanced and the backfire should cease. If not, look for leaks in the exhaust system starting at the manifold and everything to the tailpipe. Hope this helps. Happy Motoring! ...Jim'85TE

 

PS Not to cast aspersions on your mechanic, but if he, or anyone, says that Dellortos are like Webers or Weber Clones, than it's a pretty good bet that they don't really understand Dellortos. Dellortos and Webers are both side-draught carburettors, but that's about where the similarity ends. Dellortos are unique and do require different methods to properly tune them. If they have gotten good results in the past using an EGM or CarbSynch, they merely stumbled into it.

[Guest gavinc]

and some more...

dellorto.zip

[Guest THE COACH DRIVER]

and some more...

Thank you very much will have a play and see how i get on

Regasds

Mick

[Guest salty_monk]

Good luck with it... Give you something to do on New years day. You can make something similar to the Morgan tune yourself, I think I have a link to plans somewhere if you're interested.

 

Dan

[Guest Stuartl]

Good luck with it... Give you something to do on New years day. You can make something similar to the Morgan tune yourself, I think I have a link to plans somewhere if you're interested.

 

Dan

 

 

>>>>>Give you something to do on New years day.

 

Ah yes, the neighbours will love the revving of a Pinto with the occasional backfire on New Years Day!!!

 

It reminds me of when I hooked up Weber 40's to my Sylva Striker xflow, what a nightmare although the problems were down to worn carbs and engine. A mate put twin Dellorto's on his zetec engined Striker and the car ran like a dream so best of luck

 

Oh, and Happy New Year Everyone!!!