weber throttle plate and jet sizes gas mileage

[Chance]

rebuilding my weber 32/36 Dgav the primary throttle plate has gaps (see picture) im think inking of replacing it. are these gaps going to affect the way the carb runs.

secondly jet sizes I got 135 primary main jet, 160 primary air corrector, and 60 primary idle jet.      then      140 secondary main jets, 170 primary air, and 50 primary idle. then what got be asking questions was the rebuild kit came with a 200 needle and seat but the one that was in my weber was 250 and I got to reading and some said the 250 make it run real rich and should be used for higher power applications. the car was running real rich so any info on all this would be greatly appreciated. 

Edited July 19 by Chance

[datzenmike]

That's normal. The small air gap is to let in enough air to idle. It's adjusted with the idle speed screw.

 

Engines will run on various air/fuel mixtures specially those that are over rich. The left over unburned gas just goes to waste out the tail pipe. Generally it will run with what ever is put in them but conditions vary as to where they are being used. Sea level has the most air pressure compared to say mile high Denver so a larger jet for sea level and a smaller one for Denver. Performance isn't really affected by too rich but mileage is. You could drop your jet size slightly, save gas and have little effect on performance. The best way these days for dialing in your a/f ratio is a wide band 0² sensor and gauge.

 

14.7 is optimum air fuel so try to get that or just above 15 for idle to be sure all the fuel has more than enough oxygen to completely burn. Light throttle and cruise 14.7 for maximum mileage. Part throttle low 14s high 13s and reaching high 12s low 13s at full throttle.

[Stoffregen Motorsports]

One simple thing you can do to a DGV to gain efficiency is to remove the secondary choke butterfly. Some people just remove the plate, but I cut the shaft short too.

 

It's not much, but every small thing adds up.

 

Like this -

 

[Chance]

1 hour ago, datzenmike said:

That's normal. The small air gap is to let in enough air to idle. It's adjusted with the idle speed screw.

 

Engines will run on various air/fuel mixtures specially those that are over rich. The left over unburned gas just goes to waste out the tail pipe. Generally it will run with what ever is put in them but conditions vary as to where they are being used. Sea level has the most air pressure compared to say mile high Denver so a larger jet for sea level and a smaller one for Denver. Performance isn't really affected by too rich but mileage is. You could drop your jet size slightly, save gas and have little effect on performance. The best way these days for dialing in your a/f ratio is a wide band 0² sensor and gauge.

 

14.7 is optimum air fuel so try to get that or just above 15 for idle to be sure all the fuel has more than enough oxygen to completely burn. Light throttle and cruise 14.7 for maximum mileage. Part throttle low 14s high 13s and reaching high 12s low 13s at full throttle.

with everything out it still had the gap in the throttle plate, ill look into the a/f guages

[datzenmike]

I would do that if there is a problem with jetting. It's unlikely. For now I would read the plugs. Take for a 20 minute drive on the highway with a plug wrench. Pull over safely and check them. Bright white porcelain is way too lean, black or very dark is too rich, off white, cream, light tan is good.  

 

 

 

I put motorcycle carburetors on my car and re-jetted them. Turns out the original jets would have been good enough. I ended up just slightly smaller.

[Stoffregen Motorsports]

There's a hard stop on the baseplate that contacts one of the linkage pieces. It's normal to have a gap of light around there.

 

Does it idle too high? If not, then it's working the way it should.

 

[Chance]

appreciate the info, do y'all know anything about the size needle and seat? 

[datzenmike]

You say running rich but there are lots of things that can cause this that should be looked at first. Did you look at the plugs for a rich indication? Is the choke on? Could the float be set too high? is it flooding?

[Chance]

4 minutes ago, datzenmike said:

You say running rich but there are lots of things that can cause this that should be looked at first. Did you look at the plugs for a rich indication? Is the choke on? Could the float be set too high? is it flooding?

yea I have a previous post on the plugs with pictured that's the reason im rebuilding it I haven't put it back in yet to tune it and do all that stuff just curious on what the different size needle and seat do 

[Stinky]

Running rich..

The 1st thing that I think of is excessive fuel pressure.  I don't know the amount, but Webers need about 2-3#.

[datzenmike]

On 7/19/2024 at 11:55 AM, Chance said:

the car was running real rich so any info on all this would be greatly appreciated. 

 

 

Like how 'too rich'. This is rather subjective. Are the plugs black??? Black smoke out the tail pipe??? Do you have a wide band and have numbers??? Just asking what you consider too rich.  

 

Is the choke on?

Air filter badly plugged with dirt?

Excessive fuel pressure pressure, sunken float, dirt caught in the needle valve, jets can loosen and fall out. All these can over fill the carburetor float bowl. What happens is it over flows into the intake.