Looking for opinions on my engines jetting from all you weber gurus

[68Datsun510]

Looking to see what the DGV gurus of Ratsun have to say about my carbs jetting. To say the least, the jets seem...extreme...for such a mild street engine...

 

I have a recently built L19 , its an L18 block, L16 rods, and Z22S pistons, with a closed chamber A87 head with port work and a valve job by Rebello Racing. It cc'd at 1858cc's with a CR of 10.1:1. Cam is a Cal Cams 27-D, beyond that, i know nothing about it except its a bit angry under 2k and has a lumpy idle.

 

Induction is a weber DGV 5A on an L16 manifold.

 

Jets are: (primary/secondary)

Idle 50/50

E-Tube: F50/F6

AIr Corrector: 160/190

Mains: 160/220

 

It starts ok, runs well, but im getting atrocious gas mileage, despite correcting ignition issues. Also, you can smell that its quite rich. I know locals with 44 mikunis getting better in town mileage :/

 

 

Whats 'normal' jetting for an L18/20B?

[jefe de jefes]

http://www.retrospeed.org/carburadores-weber-tabla-de-reglajes/

[ggzilla]

Your engine sounds neither mild nor normal.

 

But in any case the normal jetting for stock L16, L18 and L20B that RedlineWeber supplies is:

Main Venturi: 26/27

Aux Venturi: 3.5/3.5

Main Jet: 140/135

Em Tube: F50/F6

Air Corr Jet: 165/160

Idle Jet: 55/50

Pump Jet: 50

Needle Valve: 2.00

 

First thing you should check is the venturi size, because if you don't have 26/27 venturis all the other numbers do not apply.

[68Datsun510]

Oh ok so its not 'mild' per se, but its definitely not a fire breather like those 2.3L L motors out there :P

 

Installing a Pegasus bearing kit tonight, Ill come back with more info.

[Stoffregen Motorsports]

Cody, this is not an opinion issue. It's trial and error.

[Stoffregen Motorsports]

If you're looking for mileage, you could always hook up the vacuum advance. But be careful...

[68Datsun510]

Im just lookin to see if other people who have tuned webers for specific engines in the past may look at my jetting and say, WHOA, thats not right, or whatever. I dont have any jets to swap, just testing the 'waters'.

 

Im actually in the middle of that right now, but dont worry, im going to be using a whole different dizzy anyway. THe one i have is a race dizzy. Theres no way to make the vac plate work, as that late model EI conversion pretty much jammed everything up tight.

 

I have a nissan blackbox dizzy, with 11 degrees mech advance. Set initial at 21, +11, =32 degrees max. The vac has a 15 degree swing. As you said, trial and error, need to knock test, that adjust accordingly.

[Stoffregen Motorsports]

Just be careful. You can't always hear the high RPM knocks. You know, the ones that break rings.

 

I would set up another dist with the same amount of advance, but a stronger spring and hook vacuum up to it and see what you get. That way the total advance is limited mechanically.

[hang_510]

with a CR of 10.1:1.

 

beyond that, i know nothing

 

 

Mains: 160/220

dont ever expect to gain much in MPG w/that CR.

 

start 1 size smaller in the mains.

read some more.

 

 

:ph34r:

im shooting for 20 on the canby ride. i can use 87 when i just cruise... :rofl:

 

 

are you running E85?

[yello620]

Looking to see what the DGV gurus of Ratsun have to say about my carbs jetting. To say the least, the jets seem...extreme...for such a mild street engine...

 

I have a recently built L19 , its an L18 block, L16 rods, and Z22S pistons, with a closed chamber A87 head with port work and a valve job by Rebello Racing. It cc'd at 1858cc's with a CR of 10.1:1. Cam is a Cal Cams 27-D, beyond that, i know nothing about it except its a bit angry under 2k and has a lumpy idle.

 

Induction is a weber DGV 5A on an L16 manifold.

 

Jets are: (primary/secondary)

Idle 50/50

E-Tube: F50/F6

AIr Corrector: 160/190

Mains: 160/220

 

It starts ok, runs well, but im getting atrocious gas mileage, despite correcting ignition issues. Also, you can smell that its quite rich. I know locals with 44 mikunis getting better in town mileage :/

 

 

Whats 'normal' jetting for an L18/20B?

 

I am a little surprised that you have not needed a larger primary idle jet, and your primary main seems a little big and the secondary main seems huge. But it is all trial and error, being able to read the plugs helps a lot.

 

Remember that every motor is a little different and every carb is a little different, so jetting for one carb or motor May not work on the next carb or motor that seems identical.

 

Good Luck

[68Datsun510]

Hang510, E85 isnt even available anywhere near here. ANd im glad. Your shootin for 20? mpg?

 

Im doin Canby too this year, highway fuel mileage will be tested this weekend, goin to Ginos swap meet!

 

 

And back on topic, oh the joys of carburetors :P

[ggzilla]

The higher the compression ratio, the better the MPG. If you can't get 20mpg after tuning the jets, change the gearing to keep the engine RPMs to where it works best.

[68Datsun510]

Hondas (gag, i know) are running, what, 11:1??? 30+mpg easy. AND 200HP!!! Crazy whats possible with tech.