engine and drivetrain Dcoe Tuning On New Engine -

[felix_666]

Depending on vintage, those can jam, the linkage can be mis-installed as a result

of changing the orientation of the cable pull, etc etc etc. 

 

 

I'm trying to get my head around the cold start circuit. The orientation is of concern. The levers are currently tensioned by their springs, I assumed this position to be off, as it appears they are snapped back, or shut, but it would certainly explain why the car starts so well and then runs like crap... A potential major oversight - I'll check this weekend amongst other things. Learning, learning, learning....

 

Thanks for your persistence Toby. 

 

Ok, upon checking other things I noticed a difference in the alignment of the butterfly relative to the progression holes for the idle position for the rear carb.

 

I'm guessing this is a bent shaft? How bent is bent? I'm guessing these need to be exactly the same, right?

 

 

 

 

 

Edited August 21, 2014 by felix_666

[Preyupy]

If these carbs were on a different engine before there is a very good chance that the jets have been drilled by someone. YOU NEED TO MAKE SURE THEY ARE WHAT YOU THINK THEY ARE! I recomend 45F9 idle jets to start with, the idle mixture screws should be 1-1.5 turns open. Be very careful about tightening the mixture screws down you can damage the carb body (this may have already happened) and it will really mess up your ability to get the idle mixture adjusted correctly.

It looks like you are running the thick rubber O ring style isolator style carb>manifold gaskets, if they are not torqued down correctly they are prone to air leaking. Be very careful you can over tighten them and break the ear off the carb!

Make sure the floats are working correctly and set properly. If they are Brass take them out and shake them, make sure they don't have any fuel in them. Brass floats should be set at 8.5mm, plastic at 12.5mm.

[felix_666]

If these carbs were on a different engine before there is a very good chance that the jets have been drilled by someone. YOU NEED TO MAKE SURE THEY ARE WHAT YOU THINK THEY ARE! I recomend 45F9 idle jets to start with, the idle mixture screws should be 1-1.5 turns open. Be very careful about tightening the mixture screws down you can damage the carb body (this may have already happened) and it will really mess up your ability to get the idle mixture adjusted correctly.

It looks like you are running the thick rubber O ring style isolator style carb>manifold gaskets, if they are not torqued down correctly they are prone to air leaking. Be very careful you can over tighten them and break the ear off the carb!

Make sure the floats are working correctly and set properly. If they are Brass take them out and shake them, make sure they don't have any fuel in them. Brass floats should be set at 8.5mm, plastic at 12.5mm.

 

As per my earlier post, the jets mentioned are what I've pulled out of the carbs after having them cleaned up and all new gaskets and some new jets.

 

Carbs were previously on another 02.

 

I can only assume the numbers on the jets to be correct, or is this incorrect?!

 

Cheers

 

 

Edited August 26, 2014 by felix_666

[Preyupy]

I have been working on DCOE carbs for about 35+ years and I can't tell the difference between a 125 and a 140 just by looking at it if I don't have one to compair it too. ASSUMING they are what they say they are is a very bad way to trouble shoot your problem.

When I find jets that have been drilled, I throw them away!

[FB73tii]

I have inspected the jets with my own eyes.......I can only assume the numbers on the jets to be correct?!

 

As Byron said, numbers on jets will not be correct if they were later custom drilled. Only way to be sure is to measure the holes with a wire gauge or set of wire drill bits. While one might think a very small increase in diameter won't mean much, since the cross sectional area and thus flow are proportional to radius squared, a small diameter change has a noticeable flow effect.

 

As a side note, I feel your pain! I inherited a set of 45DCOE's on a car I bought and they have been nothing but trouble for the past 2 years. Though they are Italian, they are not a proper 15/16 matched set. They are both 15's, and one has been worked on because the lead passageway plugs have been drilled out, then filled with epoxy to close. I rebuilt them but they still won't tune. New floats/jets/emulsion tubes/different float settings, etc. I have seriously contemplated just crushing them. But that's a story for another day! --Fred

[TobyB]

Your back throttle shaft is not quite properly square.  Bent?  Maybe.  Or the throttle plates are....

 

They need to be identical like the front ones are.  You can easily bend the shaft with 2 crecent

wrenches on either end of the carb BUT that's pretty scary.  You can also bend the throttle plates

just a bit, and that's scary too.

 

But it needs to be done.

 

I suppose you could REPLACE the rear throttle shaft, but that's a ton of work.  And I'm lazy.

 

Keep at them- you find that you learn more every time you work on them, and that you get

them to run a bit better incrementally.  Suddenly you realize 'shit, I actually know what's going on here'.

But that takes months, at least.

 

hth

 

t

And Fred, I think we should get together, make a big pile of magnesium dust, light it,

and throw my Spanish  disasters and your Italian fiascos onto it.

 

And wear welding goggles to watch.

 

t

[Guest_anonymous]

Both pump jet sets say 40, jet on top from a used set of 40DCOE 151, jet on bottom from a set bought from Pierce Manifolds.

[visionaut]

Both pump jet sets say 40, jet on top from a used set of 40DCOE 151, jet on bottom from a set bought from Pierce Manifolds.

"Hey, those don't look alike at all..." 

[TobyB]

I think the upper one lies...  holy cow, hogged out with a 1/16" drill bit?

 

t

[felix_666]

Ok, I got it. I need one of these huh?

 

[felix_666]

Did a little more digging today. Here's what I found:

 

Idle jets: F9/55 are brand new, so I can only assume these to be true to their size.

 

Floats: 8.5 mm - they were within 1 mm of spec to begin with. No sound of fuel inside the floats.

 

No obvious leaks, first used smoke and then ran the engine and sprayed carb cleaner about.

 

Cold start circuit seems good, no binding, no gum, etc. The starter valves appear to be seated when the levers are "off". When I pushed the valves up they came back into the seat neatly. One of the arms of the levers that pushes the valve up is broken, see picture. This shouldn't effect anything as I'm not using them.

 

I was really hoping the cold start circuit was the culprit as it would have explained things well. The search continues...

 

Edited August 24, 2014 by felix_666

[M3M3]

As a side note, I feel your pain! I inherited a set of 45DCOE's on a car I bought and they have been nothing but trouble for the past 2 years. Though they are Italian, they are not a proper 15/16 matched set. They are both 15's, and one has been worked on because the lead passageway plugs have been drilled out, then filled with epoxy to close. I rebuilt them but they still won't tune. New floats/jets/emulsion tubes/different float settings, etc. I have seriously contemplated just crushing them. But that's a story for another day! --Fred

 

this is where folks not familiar with sidedrafts get in trouble (not you fred...).  just because it says "40DCOE" on both carbs, does NOT mean they are the same.  the number to the right of the DCOE is important and the provenance of the carbs is important.  the value of a matched, known set is huge.  I was lucky enough to have had a matched set of 40's come on one of my cars, then found a NOS set of italian 45DCOE 15/16's.  they were about as turn key perfect as carbs can be.  both of those carb sets are now in the hands of FAQ'ers doing resto's.  40's on a 2002 and the 45's on a NK.  someday i hope to get to see them running again! 

[felix_666]

UPDATE:

 

JETS:

Measured all the jets, everything seems to size up, except barrel 4 has a different air corrector, but I don't think this probably has much to do with my issues, none the less I have replaced it with a 180 and have a set of 190's on the way, for comparison.

 

Not sure how big the emulsion tube holes are meant to be, does anyone have a reference?

 

 

 

FUEL PRESSURE:

Hooked up the gauge and found pressure to be between 3.5-4 psi, too high right?

 

 

I've ordered a regulator: 

 

 

FLOATS:

Float measurement after idling = 23 mm (YES I know, too high)

 

I'm guessing this is partially responsible for the poor idling conditions which appear to be from a very rich idle mixture, even though the idle mixture screws are 3/4 of a turn from seated - or are they compensating for the excess pressure/fuel...

 

 

 

 

SPARK PLUGS:

NGK: BP5ES

 

Super fouled.

 

I'm guessing this is partially from the overzealous pump pushing excess fuel into the bowels, but I also think that due to the idle mixture screws being so close to seated the idle jets are far too rich.

 

 

 

NEXT STEPS:

• Install regulator
• Run engine
• Check again for leaks, but I'm pretty certain I don't have any - all spark plugs are equally fouled.
• Check balance again
• Try to set all in timing
• If still rich then I'll stick the new set 50/F8's in

 

Edited September 17, 2014 by felix_666

[TobyB]

 

pushing excess fuel into the bowels,

Oh, that's just not a good image for troll week, that isn't...

 

Yes, if the fuel level in the carb is too high, fuel will leak into the

throats by a number of methods, none too good for a nice, lean idle.

 

So did you notice any pulsation in the gauge when the engine was running?

If pressure is spiking, it'll push past the needles and flood the bowls pretty quickly,

even though the average pressure isn't particularly high.  3.5 ISN'T too high, exactly,

but it's way up beyond what most of us like.

 

Hey, that said, the float valves aren't particularly huge, are they?  That makes 

a carb more sensitive to fuel pressure.  And they're sealing well, too, right?

 

As to Marshall's concern about matched bodies, your pictures of the progression

ports would lead me to consider them 'matched' as much as the bodies can vary.

Once the progressions are matched, the rest of the thing can be coaxed and 

blugeoned into behaving, more or less...

 

So drop the fuel levels, get a regulator on it, and see what happens.

I have to warn you, when I had a problem with a 'pulsy' fuel pump, it

beat the crap out of a generic Holley regulator in short order...

...I wonder if that's what's going on with yours...

 

hth

 

t

[felix_666]

Oh, that's just not a good image for troll week, that isn't...

 

 

lol

 

Yeah I noticed plenty of pulsation in the needle, especially at idle. I figured it was cause the pump is mechanical, like an oil pressure gauge without something to smooth it out each stroke of the pump.

 

I was wondering what happens to the excess pressure between the pump and the regulator. If the single speed pump keeps on pushing fuel but the regulator is trying to limit the flow, something must not be happy, right?