Dellorto Issues

I just replaced my EMPI EPC34 Carbs with Dellorto DLRA 40's.

I love the new linkage, the idle is much smoother, the carbs are more responsive and the car just runs better.

I do have a couple of minor issues and wondered if anyone can make some suggestions.

First, it's a little flat on acceleration and it's actually a bit slower than the EMPI's on acceleration.

Second, it pops pretty good on deaccelleration, which I'm told can be a bit of a fire danger.

Any suggestions?

Thanks!

Have you synchronized the carbs? Have you made sure your valves are adjusted properly? Is your timing set to 28- 30 deg total advance (at 3000 RPM)? Do you have a wide-band A/F meter? Is it rich, or lean?

It's pretty hard to diagnose something without some specifics.

Carbs synched, valves newly adjusted, timing good. Don't have one of those meters.

Thanks.

Might have to adjust the accelerator pumps (stroke volume) on each carb.

Cole -- before blindly adjusting things, tell us:
What size engine?
What size jets on carbs: idle, main gas, main air, accel pump; and what size venturi.
If you've got something like a 1.9 liter, you are looking for the neighborhood of 34mm venturi. Then 140 main gas jets are as big as you want to go, and use 180 main air jets. Your idle jets should be 60 mm.

Once you have all the right size "holes" and the carbs are air and mixture balanced, and it idles well and smooth GENTLY accelerating from 1000-2000 rpm, then look at your accelerator pumps. If your accel pumps are not pumping enough, then you will get a very noticeable (loud) bang from the exhaust when you stab the throttle.

I don't have a scientific method for adjusting the pumps. But I have started with adjusting them all the way off. Then stab the throttle and notice the bang (you Will notice!). Then adjust them On until it doesn't bang any more. Then give it another turn or two, to be sure. I think it is ok to over-rich it a little. It is never ok to be lean.

If you blindly crank on more accel pump, you don't know if it is already cranked on too much. Too much pump kind of floods the engine and it bogs down until the excess fuel is burned away (in black exhaust).

Cole - If you do need to goof with the accelerator pumps for stroke volume, you can make your own gauge with an eye-dropper (with increment markings) and wire. Verify the proper volume of fuel your accelerator pump should be putting out when fully activated (example: 0.8cc), then make that volume determination on your eye-dropper. Volume can be measured with a simple syringe (with cc markings). Use the syringe to draw up water in the volume desired, squirt into eye-dropper, mark eye-dropper with pen. Voila!

With engine off and using the wire, position the eye-dropper below the accelerator pump jet in the carb throat. Activate accelerator pump with full stroke. Measure volume of fuel in eye-dropper. Adjust pump lever as needed.

...or you can order this from Stoddard...

http://www.stoddard.com/shop/shopexd.asp?id=9734

Best of luck! Oh, and of course "Welcome to The Madness"!!

Success! Thanks for the tips and ideas.

I bought these from Italy and the seller was to jet them for my altitude, 5000 feet. However I found the air was 200 and the mains at 135. I've opened them to 145 and things are SOOOOO much better. Acceleration is so much better, it's like a different car!

I'm going to bump them 150 and see how that does. I can tell when they are too lean, but how can I tell if they are too rich? I don't have that piece of equipment that was mentioned.

Don't forget the Idle jets!
The carbs run mostly on the Idle jets until somwhere around 2500 or 3000 rpm.
Example:
I'm running a 2074 type 1 with dual 40 dellortos, 8.5 compression vacuum advance dist.
With 55 idle jets (Checking with a wide band AFR system) it runs around 15 - 16:1 AFR. That's a little lean.
With no changes but Idle jets at 60 my AFR changes to around 13 or 14:1. That's about perfect and it runs a little richer and cleaner. It used to pop (in the exhaust system) at constant rpm around 2000 and pop on decel.
That's all gone with the 60 mains.

The difference in MAIN jet changes are hard to see until you run at Freeway speeds or higher.
Greg

Good news Cole. It sounds like you are on the right track -- and may already be where you want to leave it.

I can see what your guy in Italy did in trying to jet for your altitude (smaller main gas, larger main air). Since he is not intimate with your particular engine, the best he could do is an educated guess, and he guessed quite close.

This article explains the "theory": http://www.racetep.com/weberaltitude.html

It is written for the poor pitiful blisters who only have Webers, but the "theory" applies to those of us higher on the food-chain with Dellortos as well. Just don't try to use those Weber jet sizes in your Dells!!

Oh! I'm sorry . . . . was it something I said? lol

Greg, you old biker......

How do you get enough manifold vacuum to run a vacuum advance disti?? I would LOVE to trash this "009"!!

You running an equalizer tube or sumthin?

Gordon,
The left carb on Dellortos has a vacuum port. It's the port at the base with the little black rubber on it.
As I recall, when I checked that port I was seeing 8.5 - 9.0 in. of vacuum there at idle. I was going to tee to the other side, but that one side is good enough to pull full vacuum advanced on the distributor.
The distributors vacuum advance pulls aprox 30 degrees, plus it has centrifical weights. The company (WWW.Hot-Spark) recommends no more than 42 degrees with vacuum advance hooked up @ 3500+ RPM.
I've got mine set a little less than that. No ping, runs great. I'd be hard pressed to say it's way better than the 009, but so far, my eng. runs lots smoother. However, some of that may be the tuning I've been doing with the aid of a Wide Band AFR set up.
I've gone from 55 idle jets to 60's for a big improvement. Next step is to go to 58 idle jets (CB Performance claims to have them) to get the AFR a little closer to Lambda. It was pretty lean 15-16:1 AFR, now it's just a tad rich @12-13:1 AFR.
NOTE: Both readings are an average of all around driving including expressway 65+MPH runs.
I got the distributor from here:
www.Hot-Spark.com/Hot-Spark-SVDA034.htm
The distributor is not quite the quality of German stuff, but so far no troubles with it. I'm running the Bosch Blue Coil that I've been running all along.

Greg

Thanks for the info. I had installed 60's for idle and it was still showing a lack of response in the mid-range so I used a torch reamer on them and reamed them out to 62.5. Not 100% cured, but improved.

Greg, I installed one of those distributors on a sand rail, along with Solex 35 PDSITs(or whatever they're called). Works very well, no stumbles, good idle, easy warmup, and more power than the Bugspray/009 he was running. Wish he had a different exhaust, but other than that all is good.

FYI: I got a Mallory SVDA w/ point replacement module from A/C.net (good people) and you need a port that shows '0' vacuum at idle and then starts to read vacuum as you open the throttle. If you get vacuum at idle then you've already started to advance your timing before the centrifugal part starts to do it's job. This was one of the best investments I've made so far to the engine. IE: It's smoother, more responsive, NO flat spot, and best of all..... Better mileage by 3mpg.
Also if you read the 'Wideband' thread on the Samba or do an author search for john@aircooled.net you'll find that 16/1 is a good setting for part throttle. It will actually let the engine heads run cooler. That said some changes to the timing will be needed since a leaner mixture does NOT need as much advance to start burning an overly rich mixture.

Been running the mains at 45 and it's running sweet! Looked at the plugs and the color is perfect.

Then one day, last Friday, it just all fell apart. Poor idle, hesitant accelleration and backfiring like crazy. At higher RPM's it runs fine and accellerates fine.

My mechanic called it right, a clogged idle jet. I had the fuel regulator go bad and replaced it recently. A small piece of rubber tubing from the change was clogging one of idle jets. Cleaned it out and it's running great again.

My mechanic says the clue was that it was running fine at higher RPM's (2500 or so), the mains apparently don't kick in until about then.

Cole, I hope your Wrench showed you how easy it is to access and clean those idle jets. All you need to have in your kit is a standard screwdriver, long tweezers and a two-inch piece of thin wire.
The idle jets are inside the top of the carbs, and have what look like ordinary brass slotted screw heads in them.
Loosen the idles with the screwdriver, remove them carefully with the tweezers and pull the two halves of the jets apart, then ream them with the wire. Re-assemble and re-install, careful to only snug them into their sockets with the screwdriver. Don't crank down on them.
I keep a stripped bread tie in my tool kit for just that purpose; it takes all of five minutes to clear all four of them out, and it's the first thing I check when my car seems a little off. It'll save you some cabbage being able to do that yourself.

Cole, if you don't have the book; get it! It is mandatory for becoming a Dellhead: http://www.cbperformance.com/catalog.asp?ProductID=2

I have personaly watched Corey clean all four idle jets in something like 15 minutes flat..... Of course, not having to stand on your head in the engine compartment helped cut the time down.....

Yes, I can clean the idle jets now, thanks!

I ordered the book, looks good.

Ordered and received a set of "Jet Doctors" and will install soon. They are suppose to help keep the idle jets from clogging.

I have dells on my envemo...when they are running right they are great...issues I have had are plugged jets...they are very sensative to even the smallest amount of dirt...run two filters one before the fuel pump and one after. when ever they are running "off" it almost always was an issue of a tiny piece of crap plugging a jet. oh, and check for exhaust leaks for those decel pops.

I don't think the popping is due to an exhaust leak, simply because it wasn't there with the old Carbs. I am thinking it's running a bit lean and that I should open up the idle jets.

Try backing out the mixture another 1/2 turn..... It might get 'er done....