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280z With Brand New Triple Webers, Baseline Jetting?


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Hello everyone, I just completed building my 1978 Datsun 280z Motor with pretty much all new or rebuilt parts besides the block. I'll run down everything I have and have done.

-Stock L28 N42 Block with dished pistons (not rebuilt or anything)

-Rebuilt Late E88 Head, Ported, 1.2mm head gasket

-Brand new Triple Weber 40 DCOE from TopEndPerformance with the Canon manifold

-Brand new 3-2-1 headers from TopEndPerformance which I also wrapped with header wrap

-280zx Dizzy "upgrade" with E12-80 box

-Carter fuel pump

-Also fully rebuilt 5 speed Transmission (Long gear ratios)

-Planning on getting the MSD Ignition Soon

I got the car running (extremely loud as its open headers atm) didn't have to adjust the Weber's really besides to get the idle down, drove the car and definitely have to ease into the gas, straight full throttle the car stumps for a second, could just be the car wasn't fully warmed up. My questions is if the Jets TopEndPerformance provided with the Weber's are perfect for my setup and what some of you guys think should be changed? I am very new to the Weber game and plan on learning how to tune these things properly in the future but for now I definitely would like some guidance before I get tuned. I will list below the Jets provided with these Webers

Main Venturi - 30

Aux Venturi - 4.5

Main Jet - 115

Emulsion Tube - F11

Air Corr Jet - 200

Idle Jet - 45F9

Pump Jet - 40

Pump Exh - 50

Needle Valve - 1.75

 

I will keep this post updated as I get my webers tuned and change out the jets

Edited by Ownallday
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That's a fair bit different than what works for me on a L28 e88 combo. DCOE 42 though...

Choke 32mm
2nd vent 3.5
Main 135
Emulsion F7
Air 165
Idle 55F13
Pump 40
1.5" air horns
Elevation 3,500'

A stumble off idle was my main problem and what most of my changes were made to address. The 1,100rpm to 2,000rpm was atrocious when I started.

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Main jet of 115 would be too small for andL28. 120 to 125 would be a start.

Idle jet of 50F9 may help.

Q. Is your 40DCOE a 151 and are all 3 carbs the same?

 

The first 5 things to check before you tune are:

1. Screw all idle screws in and back out the same number of turns. ~ 2.5 full turns for 40DCOE151

2. Ensure throttle valves are closed all the way and rest on the throttle stops with out pressure from the push rods.

3. Ensure all linkage and push rods move the throttle valves at the same time and the same amount.

4. Ensure the fuel level is the same in all carbs and is ~ 27mm below the jet bridge.

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3 minutes ago, jitenshakun said:

That's a fair bit different than what works for me on a L28 e88 combo. DCOE 42 though...

Choke 32mm
2nd vent 3.5
Main 135
Emulsion F7
Air 165
Idle 55F13
Pump 40
1.5" air horns
Elevation 3,500'

A stumble off idle was my main problem and what most of my changes were made to address. The 1,100rpm to 2,000rpm was atrocious when I started.
 

Wow that changed real quick, and here Top End states their baseline Jetting is about 80-90% there lol. Thanks for the input

4 minutes ago, 240260280 said:

Main jet of 115 would be too small for andL28. 120 to 125 would be a start.

Idle jet of 50F9 may help.

Q. Is your 40DCOE a 151 and are all 3 carbs the same?

 

The first 5 things to check before you tune are:

1. Screw all idle screws in and back out the same number of turns. ~ 2.5 full turns for 40DCOE151

2. Ensure throttle valves are closed all the way and rest on the throttle stops with out pressure from the push rods.

3. Ensure all linkage and push rods move the throttle valves at the same time and the same amount.

4. Ensure the fuel level is the same in all carbs and is ~ 27mm below the jet bridge.

Thanks for your input. I'll look into both Main Jets as when it comes down to tuning I can have both sizes ready.

Ill see if If its worth while to get the idle jet before the tune

Yes it is a 40DCOE 151 all 3 of them are the same and brand new

My friend helped me with the webers install and after installing I can confirm the first 3 from your list were already done and working perfectly as explained. 4 will come when I get them tuned. I won't be tuning them.

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I made a number of incremental changes back and forth on ilde jets and mains trying to get it right. It got me into the ballpark, but I only nailed it down once in added an AFR meter.

My main "ah-ha" was when I switch to an F7 emulsion tube, which allowed me to find a sweet spot between way too lean and way too rich. It moved my progression point and let me run a bigger main jet and a smaller idle jet.

I haven't dyno'ed my final setup, but it was driving great.

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5 minutes ago, jitenshakun said:

I made a number of incremental changes back and forth on ilde jets and mains trying to get it right. It got me into the ballpark, but I only nailed it down once in added an AFR meter.

My main "ah-ha" was when I switch to an F7 emulsion tube, which allowed me to find a sweet spot between way too lean and way too rich. It moved my progression point and let me run a bigger main jet and a smaller idle jet.

I haven't dyno'ed my final setup, but it was driving great.
 

Thanks for the input! Seems like most people are running F7 Emulsion tube on 40s even my friends so I might have to get that. Are you running 40DCOE?

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