Dellorto Experts - Check me out Options

[bandjoey]

Car has a 1.8 that was rebuilt before I bought the car. The PO doesn't know what was done or size of the rebuild...he just paid the bill to make it run.

It has DRLA carbs. It came with a Tomlinson Tech book, and in the back of the book is written:
140 Main
9164 2
60 Idle
34Mm Main Venturi

I bought a Pierburg rotary fuel pump from a local shop and was told it didn't need a pressure regulator at the time - it had an internal regulator that put out 3.5lbs. Can anyone confirm this or do I need to get a fuel pressure gauge to test the pressure? If I need a regulator, what's the right one to get.

The motor runs strong and pulls with torque from 3000 up to 5000. Occasionally, I'll hear a small single pop from the carb when I step on the pedal, but it's not often.

However, my gas mileage stinks, and when I start the car after it's been sitting for a few days, there's the distinctive smell of the old lawnmower starting up - that pukey gas smell out the exhaust. Within a couple of minutes, the smell is gone.

I'm going to go through the entire trouble shooting process this weekend from the book. Valves, timing, sync the carbs, and adjust the mixture etc.

??? Exactly what do the numbers above mean and mean to me? Are these carbs a good size for a 1.8ish motor? Suggestions of what to look for with bad gas mileage? Any DFW Dellorto experts that want to supervise? Thanks All.

(yeah Clay, I'm going to work on the FI back on this winter (IMG:style_emoticons/default/smash.gif) )

[70_914]

I ran the DRLA 34's on a mean 1641cc bug motor and it ran great. Rich of idle, great at high RPM. I ran an MSD coil, 009 distributor and my Bosch Super copper plugs gapped to .060" to keep from fouling anything. I imagine these carbs are a much better fit on a 1.8. I did not run a fuel pressure regulator.

The single pop could be one cylinder out of sync with the rest and loading up.

What kind of fuel economy are you getting? "Poor" economy is kinda vague... Dual 2 barrel carbs on these engines don't like to putt around town, there is going to be a trade-off. If you tune the engine to make good power from 3-5k rpm, then it will run poorly at idle and at 2k rpm when you are cruising around town.

If you want to get in, start your car and just drive then you need to put your fuel injection back on. If you want your car to run good around town and have good throttle response but limited high end power, get single barrel carbs. If you like to rev the (IMG:style_emoticons/default/stromberg.gif) out of your car and scream around at high rpm, keep the dual barrel carbs and deal with the limitations.

There will be 20 different answers if 25 people respond to this thread...

[nathansnathan]

I bought a carter rotory pump that claimed to put out 3.5 psi, but my gauge puts it at over 5psi. Yours is probably about the same. I got a holley regulator, and put it to 3.25psi.

Those numbers are your main gas jet, emulsion tubes, idle gas jet, and main air venturi sizes, which sound about right for a 1.8.

The pop to me sounds like a problem with one of your accellerator pump diaphrams. You can check that by taking off the air filters, and pumping the llinkage while looking down the carb throats, the car turned off. You should see a squirtgun like stream down each barrel, a shot past the butterfly valves. Probably 1 or so is not firing on account of a dry/ brittle/ cracked diaphragm, and that makes it lean then, thus the pop.

[ahdoman]

Your distributor is going to matter also. If you're using something like a Bosch 009 you won't get enough advance and you have to compromise on the curve. The car will either run good at low idle and stumble over about 4500 or stumble at low and then run good over 3500 RPM. You will get the carbs right at either one end of the curve or the other but not both if you are using the 009. I agree with Nathansnathan on the accel pump as well.

[bandjoey]

Thanks guys. Is the distributor marked somewhere visible to know what I have?

[anderssj]

Hi Bill,

FWIW . . .

I'm running a pair of Dellorto DRLA 40, purchased at CB Performance in 1982. They originally came with the venturis and jets as you listed, but I made a few changes as follows:

30mm venturi (down-sized from original CB setting @ 34mm)
55 idle jet (down-sized from original CB setting @ 60)
135 main jet (down-sized from original CB setting @ 140)
180 air correction jet (original CB setting)
9164-2 emulsion tube (original CB setting)
35 pump jets (I think--but they're the original CB setting)

I have a fuel pressure regulator on it, but can't remember the brand name. I think it's set for 3.25 or 3.5 psi.

The engine is a 73 2.0 (GA) rebuilt with a euro PC set and an Elgin cam (7008-4). It's running a re-curved Bosch 050 distributor w/ about 12* to 13* initial advance with 30* full advance (unfortunately I've lost the spec's on the recurve, but am planning on going back and figuring it out soon). We put it together back in 1981.

I made the changes to carbs as they were running rich when I first installed them. Also, it seemed that the venturis were a little too large for my displacement (stock 2L (1973cc?)).

The car now has 234+K miles (turned 234,567 miles last Sunday), over 124K with the Dells.

I've got some tech articles I can e-mail to you if you send me a PM w/your address.

Hope this helps.

Best,

Steve A-