Keep Dellorto DRLA 45s and Bosch 009? Options

[MarkV]

In your carb pic the vacuum advance port isn't capped off ??

I don't believe those ports are active on Dellortos. Mine were not.... I put rubber plugs on them but when I put a vacuum gauge on them I never got a reading.... I think the carbs have to be drilled for those to work.

[Elliot Cannon]

My carb experience has been with Webers but your symptoms to me indicate what in my case were clogged idle jets. Also possibly an intake leak. I use the Petronix Flamethrower distributor and have had good service from it for 5 years now. The body of this Petronix is also very wide and took some tweeking of the cooling tin to install.

[Mark Henry]

I think the black and red caps are interchangeable and the red came on the newer models.

No, they're not interchangeable.

[porschetub]

In your carb pic the vacuum advance port isn't capped off ??

I don't believe those ports are active on Dellortos. Mine were not.... I put rubber plugs on them but when I put a vacuum gauge on them I never got a reading.... I think the carbs have to be drilled for those to work.

Some carb sets come with only 1 port in the pair,can't remember if its the left or right one ,the 2 ex- Alfa sets I have are that way,if they ports are there they are drilled and will have vacuum....least mine are.
However I read on a UK forum some sets had vacuum ports on left and right ones as supplied new.
There are 2 hex screws on each carb below the height of the throttle shaft these for balancing maximum vacuum when tuning,I believe this is because the carbs never came with velocity stacks so couldn't be balanced with a conventional synchrometer.

Not sure this engine would idle as per the supplied video with blocked idle jets....seemed to run to smooth for that.

OP needs to pull a carb and see what he has...I think that's also a good starting point also.

[MarkV]

I think the black and red caps are interchangeable and the red came on the newer models.

No, they're not interchangeable.

I think you are correct. The red has a different rotor that may only work with a red cap. The black cap rotor is round at the back and the red rotor is triangular at the back. The red cap looks like it could be taller so maybe that the difference..... the distributors all look identical. one of my distributors has a different part number ... YL-570 A2.

[Mark Henry]

Well ...I know I'm correct.

Black the can (body) is taller, cap is shorter and clips sit lower on the cap. The caps centers on a notch on the can.
I believe all the black tops must be oiled with a pin oiler.

Most red tops have an oil hole machined (auto oiling) near the drive gear, the lip of the cap fits over the can like a stock bosch dizzy cap and centers on a pin on the outside lip of the can. The notch is on the cap.
Both styles have different rotors, in fact IIRC there's about 5-6 different rotor styles.

I've had many of each style in my hands over the years.

[98101]

I don't believe those ports are active on Dellortos. Mine were not.... I put rubber plugs on them but when I put a vacuum gauge on them I never got a reading.... I think the carbs have to be drilled for those to work.

I don't have a vacuum gauge (actually there's one in the dash but I don't know whether it's hooked up to anything or if it even works) but I tried covering it with my finger and couldn't detect any suction. Then I tried squirting a little water into it and didn't hear any change in how the engine was running. If I had any rubber plugs I guess I'd put those over them.

[98101]

Not sure this engine would idle as per the supplied video with blocked idle jets....seemed to run to smooth for that.

In case anyone missed it, three things the engine seems to do well: start, idle, pull like a clydesdale at wide-open throttle. Poor running seems to happen at certain combinations of part throttle and engine load. The backfires might be most common after a hard run. Temperature is in the 40s (Fahrenheit) here, and the oil temp takes a long time to reach 170ºF.

OP needs to pull a carb and see what he has...I think that's also a good starting point also.

Thanks -- I'm reading the Dellorto Tech Book now about how to do that so I don't screw something up. I'm not clear whether I can easily check the main venturi size without removal.

The book suggested I should not trust the numbers on the jets, if they are even legible, as they may have been reamed. It suggested using jet gauges. I don't have those yet. Is this taking it too far?

I ordered the carburetor synchrometer from Pelican, part # PEL-TOL-STESK.

I ordered what I think are the same 3 1/4 inch air filters MarkV is using from CB Performance, their part #3301. A lady at CB Performance named Marieanne was knowledgeable and kept me from ordering the wrong filter.

Regarding the CSP linkage, she said CB Performance doesn't carry it. It looked like MarkV had no complaints about the same hex linkage I've got, so I may hold off on changing that.

No one suggested keeping the Bosch 009, or any reason not to get the 123 distributor I'm so intrigued with. I ordered the Bluetooth 123 distributor using the group buy code. I don't think I've changed a distributor before, so thinking I might seek help with this.

The roughness at part throttle and sensitivity to engine load make me want to experiment with vacuum advance, hence the interest in the configurable distributor.

[Mark Henry]

Vacuum advance doesn't play well with dual carbs, as they have poor vacuum. If you add a hotter cam Vac becomes even worse.

[MarkV]

I didn't realize that dual carbs don't produce a good vacuum signal but it makes sense. I didn't find a port on the DRLA's with a vacuum signal and I didn't want to drill them.

I have a cross bar linkage because it came with the car and it was at one time all that was available. It's probably harder to set up but once it's set it works fine. Just make sure that both sides open at the same rate.

The jets are marked ..... easy to enough to read. You can pull a venturi with out having to remove the carb by just pulling the top off the carb. They have a cone shaped set screw on the end of the barrel. The venturi are marked. I am running 34's you made need something bigger. If you take the top off a carb be careful not to damage the gasket or inadvertently bend the float tangs and change the fuel level.

Do a search here I am sure there are a bunch of threads concerning dialing in carbs. This one is pretty useful: http://www.aircooled.net/synchronize-dual-...arburetors-103/

[thelogo]

Sorry but just want to make sure all the facts are there

You are running premium gasoline ? Correct

[98101]

Sorry but just want to make sure all the facts are there

You are running premium gasoline ? Correct

I think so. Previous owner said he was. I finally saw the low fuel light yesterday and filled it with 92.

I didn't ever hear anything resembling pinging. In Arizona both my 914s pinged a lot unless I retarded the timing so far the cars were slow.

[thelogo]

Sounds like you have a lot more experience with these cars then i do

But ive always heard dellorto s are supposed to be the
Technicallly superior carb because of their
Behavior when not at wot
Like a partial circuit or something.

So they are smoother , more street oriented then
Webbers

Thats not necessarily the story here but then again
Did the guy who built it use dellorto for a reason
Or thats just what was available

[98101]

As y'all advised, I bought an air-flow meter. I was able to measure what was happening at idle. At the time the engine was warm and idling fast, around 1200 RPM. It often idles lower than that.

With only one meter, I didn't see a way to compare the behavior at speeds other than idle. Is there some trick to this that I don't know? If not I guess I'll buy another meter(s) to watch more than one throat at a time while revving the engine. Sometimes when I'm driving, I'm wondering whether it's running right at slight throttle, just off of idle.

At idle I noticed slightly less flow from cylinder #3. It reads 5 while the others read almost 6. Is this a significant difference?

Cylinder #4 below:


Cylinder #3 below:


Idling fast at the moment:


Cylinder #2 below:


Cylinder #1 below:


I also got more legitimate looking air filters from CB Performance to replace the foam things the previous owner had for some reason. But I still have the long studs, so removing the air filters is more of a hassle than it should be. I don't know if it's easy to find shorter studs. I'm tempted to buy taller filters just to reduce the hassle.

[MarkV]

I always disconnect at least on carb from the linkage. You don't need 2 meters just move it from throat to throat. I set my idle at like 900....1200 is too fast. You adjust the idle screws on each carb to get the flow to match. Slow the idle on the carb that is flowing the most air. When you first start playing with them it can be frustrating but one you get the hang of it it's really pretty easy. Then set the mixture screws.

Get the timing set up where you want it before you set the carbs. If you change the timing after you adjust the carbs it will change your idle speed.

No reason to by new studs just measure them and then cut them with a hack saw. The studs are an american thread size I believe. I was able to buy a set at the local ace hardware.

If you cut them with a hack saw remove them first.

[MarkV]

The studs are #10 X 32 thread size.

[98101]

No reason to by new studs just measure them and then cut them with a hack saw. The studs are an american thread size I believe. I was able to buy a set at the local ace hardware.

If you cut them with a hack saw remove them first.

Cool -- thanks!

I don't know why it was idling so high this time. Usually it's idling around 900. But usually I don't get to drive it long enough to warm up much.

[MarkV]

I fought with mine when I first set them up. Make sure that the linkage on both cars are symmetrical. The rods that attach from the linkage to the arm on the carb should be the same angle... otherwise one carb is going to open at a different rate than the other. You can operate the linkage with the car running manually to check the flow at higher rpm. I try to hold it at 2500 rpm and compare one carb to the other to ensure the linkage is working correctly. Set the idle with one side disconnected and then reconnect and make sure that there is no change in rpm when you reconnect... adjust the rod if you have to so that the rpm doesn't change.

I noticed in your photos that there is a spring on your throttle cable. I have never seen that before. My carbs have springs built in to the throttle shaft. That extra spring may be causing your idle to change with engine temperature. I have my cable adjusted so that there is a little bit of slack in it so that as the engine heats up it doesn't pull on the cable and change the idle. You might try eliminating the spring on the cable.

[MarkV]

Maybe this will help you:

https://www.youtube.com/watch?v=5tigMg-Fn94


He doesn't go into making sure the linkage is set up correctly or how to check it at rpm. It is a simple explanation of how to set the idle.

[thelogo]

Yeh that throttle cable spring is intresting

And id say idle speed varies a little bit
But 1200 is on the high side

Once again ive heard dellortos
Are the smoothest as far as partial throttle is concerned