DCOE help
01-16-10, 06:06 PM
#1
DCOE help
Ok, what I have. stock 12a, 45 DCOE 9 (70's model), Gen.2 alt. and fuseblock, DLIDFIS w HEI, RB dual exhaust header to muffler, Holley "red" type fuel pump, ebay fpr w/gauge, inline clear fuel filter, Gilmer drive,all new but motor and Gen.2 stuff, new plugs, wires, coils, and hoses. No rats nest or emissions. Here's what the carb has.
F11 E-tube
175 Main jets
55 Pump jets
65F9 Idle jets
36 Chokes
160 Air Correction jets
I've followed the "lean best idle" procedures and the car idles fine. But when I give it gas it stumbles/bogs and tries to die. I bought an assortmnet of jets in case I wasn't right on my first shot, but not sure what this condition indicates. Where to start, up or down on which jets? Is it jets to begin with?
F11 E-tube
175 Main jets
55 Pump jets
65F9 Idle jets
36 Chokes
160 Air Correction jets
I've followed the "lean best idle" procedures and the car idles fine. But when I give it gas it stumbles/bogs and tries to die. I bought an assortmnet of jets in case I wasn't right on my first shot, but not sure what this condition indicates. Where to start, up or down on which jets? Is it jets to begin with?
01-16-10, 08:26 PM
#2
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i dunno what reading you've done, but basically there are two circuits in the carb.
the idle circuit, and then main circuit.
the idle circuit is supposed to be under the throttle plate, and it supplies a fuel and air mix at low throttle openings.
as the throttle opening becomes bigger the main circuit starts metering fuel.
the emulsion tube controls how fast the main circuit comes on.
soooOOOoo
#1. verify the timing.
#2. start trying stuff. pull the choke and see if the motor likes it more, or the stumble gets worse.
#3. verify that the idle speed and mixture screws are within range. i'm not sure about the DCOE, but an IDA needs the screws in a certain range to work. for example if you have the idle speed too high, the throttle plates get so far open that it uncovers the transition ports
#4 check for vacuum leaks.
off the top the jetting looks like it should work, or be close enough. you don't have to worry about detonation/pinging on an NA, unless the spark timing is wrong
the idle circuit, and then main circuit.
the idle circuit is supposed to be under the throttle plate, and it supplies a fuel and air mix at low throttle openings.
as the throttle opening becomes bigger the main circuit starts metering fuel.
the emulsion tube controls how fast the main circuit comes on.
soooOOOoo
#1. verify the timing.
#2. start trying stuff. pull the choke and see if the motor likes it more, or the stumble gets worse.
#3. verify that the idle speed and mixture screws are within range. i'm not sure about the DCOE, but an IDA needs the screws in a certain range to work. for example if you have the idle speed too high, the throttle plates get so far open that it uncovers the transition ports
#4 check for vacuum leaks.
off the top the jetting looks like it should work, or be close enough. you don't have to worry about detonation/pinging on an NA, unless the spark timing is wrong
01-17-10, 12:02 AM
#3
i dunno what reading you've done, but basically there are two circuits in the carb.
the idle circuit, and then main circuit.
the idle circuit is supposed to be under the throttle plate, and it supplies a fuel and air mix at low throttle openings.
as the throttle opening becomes bigger the main circuit starts metering fuel.
the emulsion tube controls how fast the main circuit comes on.
soooOOOoo
#1. verify the timing.
I've timed it as close as I can with the gilmer, and between the archives and what other info I've found, seems to be some conflicting info about what the timing should be with my setup.
#2. start trying stuff. pull the choke and see if the motor likes it more, or the stumble gets worse.
DCOE's have no choke. The reason for this posting was to get advice on what/where to start trying stuff. There are ALOT of possible adjustments.
#3. verify that the idle speed and mixture screws are within range. i'm not sure about the DCOE, but an IDA needs the screws in a certain range to work. for example if you have the idle speed too high, the throttle plates get so far open that it uncovers the transition ports
That's why I specified that I'd followed the "best lean idle" procedure, meaning the idle and mixture screws are within suggested range. Idle is fine as stated, but when given more than a litlle throttle, it stumbles and tries to die.
#4 check for vacuum leaks.
DCOE has no vaccuum ports and as I specified, I have no emissions/rats nest etc. The only vaccuum I have are 2 lines from the intake to the brake booster and the crankcase ventilation.
off the top the jetting looks like it should work, or be close enough. you don't have to worry about detonation/pinging on an NA, unless the spark timing is wrong
the idle circuit, and then main circuit.
the idle circuit is supposed to be under the throttle plate, and it supplies a fuel and air mix at low throttle openings.
as the throttle opening becomes bigger the main circuit starts metering fuel.
the emulsion tube controls how fast the main circuit comes on.
soooOOOoo
#1. verify the timing.
I've timed it as close as I can with the gilmer, and between the archives and what other info I've found, seems to be some conflicting info about what the timing should be with my setup.
#2. start trying stuff. pull the choke and see if the motor likes it more, or the stumble gets worse.
DCOE's have no choke. The reason for this posting was to get advice on what/where to start trying stuff. There are ALOT of possible adjustments.
#3. verify that the idle speed and mixture screws are within range. i'm not sure about the DCOE, but an IDA needs the screws in a certain range to work. for example if you have the idle speed too high, the throttle plates get so far open that it uncovers the transition ports
That's why I specified that I'd followed the "best lean idle" procedure, meaning the idle and mixture screws are within suggested range. Idle is fine as stated, but when given more than a litlle throttle, it stumbles and tries to die.
#4 check for vacuum leaks.
DCOE has no vaccuum ports and as I specified, I have no emissions/rats nest etc. The only vaccuum I have are 2 lines from the intake to the brake booster and the crankcase ventilation.
off the top the jetting looks like it should work, or be close enough. you don't have to worry about detonation/pinging on an NA, unless the spark timing is wrong
01-17-10, 10:01 AM
#4
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1. timing, if you're using the stock distributor, it should be right at TDC at idle. for the Leadings
2.3 ah ok, try richening the idle up, see if it changes. too rich and too lean can feel the same, so its really helpful to try both, especially right off idle. don't be afraid to change jets either, its super simple.
4. most vacuum leaks occur at gaskets, especially the intake to engine gasket. you may also wanna make sure its not the PCV or the booster really quick too.
5. does the accelerator pump work?
once you've made sure that there arent any mechanical problems, don't be afraid to jump in and change jets, the idle circuit is working from idle to 2000-3000rpms depending.
i'm not sure what you have but try a different one, its either going to be better or worse...
this tuning process is faster with a wideband oxygen sensor, or even a narrow band one, but you can do without, its just a longer
2.3 ah ok, try richening the idle up, see if it changes. too rich and too lean can feel the same, so its really helpful to try both, especially right off idle. don't be afraid to change jets either, its super simple.
4. most vacuum leaks occur at gaskets, especially the intake to engine gasket. you may also wanna make sure its not the PCV or the booster really quick too.
5. does the accelerator pump work?
once you've made sure that there arent any mechanical problems, don't be afraid to jump in and change jets, the idle circuit is working from idle to 2000-3000rpms depending.
i'm not sure what you have but try a different one, its either going to be better or worse...
this tuning process is faster with a wideband oxygen sensor, or even a narrow band one, but you can do without, its just a longer
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01-25-10, 10:13 AM
#8
Float level?
Ok, found out most of the original problem was ignition related. Adjusted the floats and problem got no better, then I found out that with the "high output" ignition modules you have to swap the trigger wire polarity from the dizzy. They will idle ok wired "correctly", but won't run. After swapping polarity, runs fine. Got idle set and sounds good, but if I blip the throttle it bogs and wants to die. I'm assuming it's my float settings. What height sre you guys setting your floats? Stock seems to be somewhere from 5mm to 9mm.
01-26-10, 04:06 PM
#9
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you could also put bigger chokes in. ive got 40mm. depending on your elevation. stumbling through the rpm progression is caused by too little air. or just an improper mixture. the best way to tune your dcoe is to get a wideband or fuel air ratio guage. is it sidedraft or downdraft?
01-26-10, 09:07 PM
#10
you could also put bigger chokes in. ive got 40mm. depending on your elevation. stumbling through the rpm progression is caused by too little air. or just an improper mixture. the best way to tune your dcoe is to get a wideband or fuel air ratio guage. is it sidedraft or downdraft?
01-27-10, 12:00 PM
#11
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on the IDA, we want the float as high as we can get it without gas dripping in when its running, on a DCOE i would set it to the higher end of the factory range, so the bowl is more full.
anything like an 02 sensor, will help you figure out whats going on faster, although its possible to do it without..
01-27-10, 10:32 PM
#13
Thanks guys. I decided to back track, go back to basics and elimate suspects one at a time. Dropped tank and inspected it. Ran new braided stainless hoses and blew out lines. Going out to test later. Next will be bypassing fpr and fp with old one, then floats/jets. Gotta be one of em'.
01-28-10, 01:39 AM
#15
When I was at Pick N' Pull yesterday I spotted a 45 DCOE on a VW. Does the 45 DCOE work with a IDA manifold? I also thought that DCOE didn't come as a downdraft but I have seen a few DCOE downdraft manifolds on ebay. Good Luck and keep us posted.
Last edited by Jibaro 12A; 01-28-10 at 01:41 AM.
01-28-10, 05:04 PM
#16
Yep, guys use em on VW's
The DCOE and the IDA have different mounting, so you can't interchange the intakes. If someone on ebay had an intake that was "downdraft" and said it was for a dcoe carb, BEWARE! There are intakes for piston engines,(might even be some for rotaries) that have the carb mounting on an intake horizontally, but it still sits sideways that way. If you mounted it "downdraft" style, the floats and etc. would be worthless, as the gas would just pour past and into the carb.
