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chaseincats

DCOE 40 "burn your eyes rich"

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Question for you guys - I have a friend who bought this: https://www.ebay.com/itm/Weber-DCOE-Kit-fits-Datsun-240Z-260Z-280Z-Triple-Performance-40-DCOE-K659/272778769560?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649&fbclid=IwAR1-Pa61k0L6wA2H0mXxTlwqbQ5MLFtBQT5KGbX4TlrUgjEMWnvBwIyfpWE

Even with the air mixture screw set to max-lean, the exhaust out of this car is so rich it burns your eyes within a few seconds.

Are the jets this kit comes with too aggressive?

 

-chase

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Can you post up the jets? Its as easy as popping the inspection cover and using a flathead to back out the jets.

Idle jet, main, and emulsion tube at the minimum please.

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Is your friend running a mech or electric fuel pump? Either way, a pressure regulator may be needed as Webers only need 3psi or so of fuel pressure.

Sent from my SM-G981W using Tapatalk

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16 hours ago, jitenshakun said:

Is your friend running a mech or electric fuel pump? Either way, a pressure regulator may be needed as Webers only need 3psi or so of fuel pressure.

Sent from my SM-G981W using Tapatalk
 

Since it's a 260 it has both - a mechanical pump in the front and an electric in the back.  It has an in-line pressure regulator on there set to 2.  I believe this is the regulator he has: https://www.oreillyauto.com/detail/b/mr--gasket-4367/performance-16477/engine-16841/fuel-system-16571/fuel-pressure-regulators-17798/37354b4805ef/mr-gasket-fuel-pressure-regulator/9710/4514726/1978/nissan/280z?pos=1

 

EDIT: He only has an electric fuel pump in the back set to 2.5 psi

Edited by chaseincats

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At 2 psi he isn't flooding the bowls. I'm surprised it runs rich with the idle screwed in all the way. That practically shuts the fuel off. Screwed in for lean, out for rich...

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2 minutes ago, jitenshakun said:

At 2 psi he isn't flooding the bowls. I'm surprised it runs rich with the idle screwed in all the way. That practically shuts the fuel off. Screwed in for lean, out for rich...

Sent from my SM-G981W using Tapatalk
 

Yeah, that's what's so strange about it and leads me to believe maybe the jets that kit comes with are too large?

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Check fuel levels.

- Remove one main jet assembly in each carb.

- Measure distance from top of fuel to the bridge where the main jet screws in.

 

At 23mm, the fuel will pour into the carb throat.... not good.

At 25mm down, the fuel will slosh into carb throat on bumps and such

29mm down is recommended.

31 to 27mm is a range for tuning.

 

 

fuel depth.jpg

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1 minute ago, 240260280 said:

Check fuel levels.

- Remove one main jet assembly in each carb.

- Measure distance from top of fuel to the bridge where the main jet screws in.

 

At 23mm, the fuel will pour into the carb throat.... not good.

At 25mm down, the fuel will slosh into carb throat on bumps and such

29mm down is recommended.

31 to 27mm is a range for tuning.

 

 

fuel depth.jpg

Thanks, I'll pass the message along.

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For stock 240z to 260z, here are approximate fueling need sizes:

 

Idle Jets are typically 45 to 55 (fuel hole in bottom is 0.45 to 0.55mm)

Main Jets are typically 115 to 125 (fuel hole in bottom is 1.15 to 1.25mm)

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1 minute ago, 240260280 said:

For stock 240z to 260z, here are approximate fueling need sizes:

 

Idle Jets are typically 45 to 55 (fuel hole in bottom is 0.45 to 0.55mm)

Main Jets are typically 115 to 125 (fuel hole in bottom is 1.15 to 1.25mm)

Will he have to measure the opening hole, or will the size be stamped on the jet?

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He's out of town until Monday - I'll get back to you then.  Thanks for all your help so-far.

@240260280 Gotcha on the main and idle jets, any recommended stats for emulsion tube?

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18 minutes ago, chaseincats said:

He's out of town until Monday - I'll get back to you then.  Thanks for all your help so-far.

@240260280 Gotcha on the main and idle jets, any recommended stats for emulsion tube?

E tube changes do not make a big differences except for the diameter of the tube. If you have F2 tubes then that would be very rich.  F11, F16 are typical and should be fine for initial tuning.  

Jet sizes and fuel depth would be the first things to check.

Also mechanical linkage is Very important. The throttle plates should all be closed as much as possible at idle before you attach the mechanical push rod ends.

One tuning tip to ensure the linkage is right is to pull each plug one at a time and measure how much the idle drops.... you can quickly find out if one carb is working more than the others due to the mechanical linkage incorrectly opening the plates on that carb too much. This should be done at idle and off idle to cover the bases. 

Edited by 240260280
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Have some main/idle jets & emulsion tube pictures.

It looks like they say:

  • main jet/emulsion tube: 60F6, F11
  • idle jet: 125

Any ideas?

121965577_376356930167370_7332607211011308949_n.png

122085809_442405140057192_3839834731424488345_n.png

121805916_964061447440952_8510008425318405035_n.png

121805916_964061447440952_8510008425318405035_n.png

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Idle jet lean to rich goes:

 

F3, F1, F7, F1, F4, F2, F13, F11, F8, F9, F12, F6

 

At 60 I'd say the pig rich is because it's the richest possible AND too big.

 

 

Lean to rich on Emulsion goes:

 

F11, F15, F16, F2, F8 and F7.

 

The F11 you have is a lean choice, but emulsion tubes are a bit tricky. They change how and when you main jets work under acceleration, so impact how much the idle has to do.

 

The 125 main jet might be about right.

 

For now, I'd scale way back on the idle jet, like 55F2, and leave the main and emulsion. I prefer to go one step at a time but 60F6 is way out there.

 

I run a 55F13 on my L28 block.

 

 

 

 

 

 

 

 

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1 minute ago, jitenshakun said:

Idle jet lean to rich goes:

F3, F1, F7, F1, F4, F2, F13, F11, F8, F9, F12, F6

At 60 I'd say the pig rich is because it's the richest possible AND too big.

For a L24 try a 55F2.

Lean to rich on Emulsion goes:

F11, F15, F16, F2, F8 and F7.

F7 is a pretty safe bet, so the F11 you have is an interesting choice.

The 125 main jet might be about right.

For now, I'd scale way back on the idle jet.

Sent from my SM-G981W using Tapatalk
 

Awesome info, thanks!

The car has an L26 instead of an L24 - would that change any of these ratings or are those pretty universal for all L-series engines?

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Awesome info, thanks!

The car has an L26 instead of an L24 - would that change any of these ratings or are those pretty universal for all L-series engines?

The "book values" sometimes lump the L24 and L26 values together, which doesn't make complete sense. No engine runs exactly the same so I'd always be prepared to move "off book" with Weber jetting.

 

I run an F7 emulsion tube and the only place that said that was the way to go was the Deshammill book; all the online Datsun stuff said I should run a leaner emulsion tube.

 

In this case I'd have a hard time believing the 60F6 idle jet is the right one for the L26. I'm sure it guarantees the car will start when you bolt on the Webers by virtue of being so rich, which might be why they spec the kit with them.

 

Sent from my SM-G981W using Tapatalk

 

 

 

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