Weber DCOE Dizzy issue

[SIVAllan]

I've been installing a Holbay clone motor in the Airpine on a piece by piece basis.

The motor has Coltec flat top pistons, a Holbay head, performance exhaust header and a fast road cam.

It dyno tests at 70 bhp at the rear wheels using twin WIP Zeniths and is under carbureted.

Next step was to install dual 40DCOE35 carbs but I decided on a single, large carb instead to avoid the hassles of stuff in the engine bay being in the way.

So, using a custom intake header from Bill Atalla, I installed a 45DCOE151.

The big Weber is idling but not idling great.

One issue may be the distributor - it's a vacuum advance dizzy but the Weber and intake have no connection for the dizzy vacuum line.

Currently the vacuum line is hanging in space, connected to nothing.

What are the options?

The h120 motors used a mechanical advance dizzy but I've been unable to find one.

Thanks in advance,

Allan

 

[RootesRacer]

You almost surely will have to go fully mechanical since the weber will not have an equivalent vacuum progression holes and since your intake has no plenum it wouldnt function the same anyhow.

What you need to do is to recurve the dizzy to have fewer degrees mechanical advance (16 to 18 crank degrees at 3500rpm where the mech adv hits its stops) will be about right, then set the timing so that you get 32 degrees at 4000 RPM.
Your idle timing is what it is, but will be at 14 or so degrees. The high RPM timing is what matters.

To recurve, you will need to have the timing advance stop tang welded so it doesnt move as far as it did, you will have to measure the unmodified movement range (knowing its cam degree advance number which is stamped on the mechanism) and interpolate to the 16 to 18 crank degrees you will end with. Keep in mind the cam degree number stamped on the mechanism is doubled for crank degrees and depending on the distributor year will be a number that is 11 to 13 or 22 to 26 mechanical crank degrees.

You then will test the actual advance rate and if needed, increase the spring tension to get the 16 to 18 crank degree change at 3500 RPM.

Hope this was clear enough.

 

[Mike snyder]

I ran into the same problem with 2x 40DCOE. I had advanced distributors (advanceddistributors.com) rebuild my distributor for full mechanical advance with a pertronix electronic ignition. They were not cheap but did a stunningly good job and I highly recommend them.
mike Snyder

 

[RootesRacer]

I ran into the same problem with 2x 40DCOE. I had advanced distributors (advanceddistributors.com) rebuild my distributor for full mechanical advance with a pertronix electronic ignition. They were not cheap but did a stunningly good job and I highly recommend them.
mike Snyder

Did they tell you the timing specs on what they provided?
Thats not something you want to take a cookie cutter approach with.

 

[Mike snyder]

yes, Jeff Schlemmer, (the owner) had me fill out a full sheet on all the mods I did to the engine. He also called me to clarify some details before doing the recurve and all the other mods needed to make the distributor work properly.
Mike Snyder

 

[jumpinjan]

Couldn't a vacuum hose fitting be installed in the manifold? Or is there not enough thickness in the tube runners?

 

[SIVAllan]

I suppose the metal is thick enough but
there is no plenum - just runners.

I don't know but had assumed that
Fitting to a plenum would be
necessary...?

Allan Ballard

 

[RootesRacer]

yes, Jeff Schlemmer, (the owner) had me fill out a full sheet on all the mods I did to the engine. He also called me to clarify some details before doing the recurve and all the other mods needed to make the distributor work properly.
Mike Snyder

It would be nice to see the timing numbers that the dizzy was built to.

Since the drive spindle actually needs replaced or modified by welding, it wouldnt surprise me if the timing numbers are far from what is needed for decent light load performance and fuel economy.

 

[jumpinjan]

I suppose the metal is thick enough but
there is no plenum - just runners.

Make a synthetic plenum by connecting all the runners with 1/4" tube. I'm thinking of Parker nylon tube & fittings would make it easy,

 

[Jay Laifman]

A few comments.

When I did mine (Holbay head, H120 cam, dual DCOEs, Jahns pistons), I had the help of a top Lotus mechanic. He actually ended up changing the weights and springs to what he uses in his Lotuses. Unfortunately, that was about 20 years ago and I no longer have any contact with him and don't know what he did other than that. The thing does idle all day long.

I will say though that what weights and springs you have should not cause you to have problems with idle. Idle is a constant advance point. So, it's either holding that advance or it's not. How is your distributor shaft and points? I'm actually using the Lumination set up and it has been flawless for those 20 years.

Also, while I do agree you should set up the advance at total advance, I think that having the right advance lower in the curve is also very important. I have experienced this more with one of my Porsches, which has 30 degrees of advance. Without going into a full story, the car ran much better, much more spirit and character, less odd pops from the carbs, and with even better blips of the throttle on downshifts, when I had a well set up 30 degree advance distributor than the non-stock 17 degree advance distributor many put on, simply because the 30 degree distributor is so expensive to rebuild.

The big problem is as pointed out: the correct advance curve, or the best advance curve is very engine/cam/carb specific. Many car companies spent a lot of time and testing with their engines to determine the best one. It isn't something that can really be pulled out of the air when cars get modified (as my Lotus springs and weights are a perfect example of the wrong thing to do). So, assuming Rootes spent time and money on it, I would suggest trying to get it sprung to match what they did for the H120. The problem there being, how the heck do you find out what the H120 distributor curve was? I'm not saying that their curve was the optimum curve. I just think it is likely better than all the other guesses out there. With one caveat. If Jarrid says otherwise, or has a better way to come up with a curve, go with that!

 

[SIVAllan]

I found a Lucas distributor that may be
the one needed.

The string of model numbers:

Lucas 4 | 454 A 43D4 >>>> 11/73

Can anyone verify if this is the needed distributor
for a DCOE setup?

Thanks in advance,

Allan

 

[Dodgealpine]

http://www.mgaroadster.co.uk/Technical_Information/lucas.pdf
Hope this helps, its a pdf file that lists all lucas distributors and their applications. Its a bit heavy going but it appears the 43 D4 is off a 1300 Avenger GLS. Regards.

 

[SIVAllan]

http://www.mgaroadster.co.uk/Technical_Information/lucas.pdf
Hope this helps, its a pdf file that lists all lucas distributors and their applications. Its a bit heavy going but it appears the 43 D4 is off a 1300 Avenger GLS. Regards.

Nice spreadsheet - thanks!

I put it in a browser, then did a "Find" on 43D4.

A few entries appeared, including this one:

43D4
No vacuum
1972-76
Sunbeam
Hunter GLS 1.7

I think this may be the one

Now to call advanced distributors concerning a rebuild.

Thanks!

Allan

 

[sunbby]

Allan, there are a few with H120 in the model and one with Holbay, did you see this one? If you are sending it to Advanced Distributors anyway, I think he can set the curve appropriately, even if you don't have the exactly correct dizzy to start with.

-Todd

Service number - 41239A
Model - 23D4
rot'n - CCW
ECM curve -
RPM 1 - 3000 Advance1±1° - 13
RPM 2 - 900 Advance2±1° - 11
RPM 3 - 400 Advance3±1° - 2
RPM 4 - 250 Advance4±1°
no advance below - 250
vacuum code - No vacuum
Connection -
years -
make - Sunbeam
models - Rapier Holbay H120 engine
Comments -

 

[SIVAllan]

Allan, there are a few with H120 in the model and one with Holbay, did you see this one? If you are sending it to Advanced Distributors anyway, I think he can set the curve appropriately, even if you don't have the exactly correct dizzy to start with.

-Todd

Service number - 41239A
Model - 23D4
rot'n - CCW
ECM curve -
RPM 1 - 3000 Advance1±1° - 13
RPM 2 - 900 Advance2±1° - 11
RPM 3 - 400 Advance3±1° - 2
RPM 4 - 250 Advance4±1°
no advance below - 250
vacuum code - No vacuum
Connection -
years -
make - Sunbeam
models - Rapier Holbay H120 engine
Comments -

Hi Todd,

Thanks - I wanted to see if the model number on the no vacuum dizzy that I have matched to a no vacuum Holbay 1.7, which it does as the Hunter GLS was a Holbay 1.7 engine.

Maybe other distributors were used as well on the Holbay motors?

Where did your curve info come from?

It is specific to a Holbay distributor?

Thanks again,

Allan

 

[sunbby]

That curve info just came from the lucas.pdf that Dodgealpine posted (and you loaded into your spreadsheet).

 

[SIVAllan]

Todd,

Thanks again; I see it now.

Allan

 

[Jay Laifman]

Hi Allan,

What did you end up doing?