Weber Carb Adjustment Thread

JohnnyC · 03-28-08, 12:39 PM

At one time I was quite good at tuning Weber carbs...so I figure i'll share some knowledge and maybe some of you can have some good insite also...because lets face it ...there are many weber questions

Some info i'll pull from other sites and i will note that as i go along.

JohnnyC · 03-28-08, 12:40 PM

These are observations and can be used as a base to start at:

Looking for real life applications for these #’rs

Weber cab jet sizes:

Main Jets 38/38:
Elevation:
SL (sea level) 1250ft 2500 3750 5000 6250 7500 8725+
F 150 145 140 135 135 130 130 125
2F 155 150 145 140 135 135 130 130

Air Correction 38/38:
Elevation:
SL (sea level) 1250ft 2500 3750 5000 6250 7500 8725+
F 180 180 185 185 190 190 195 200
2F 180 185 185 190 190 195 200 200

Idle jets 38/38:
Elevation:
SL (sea level) 1250ft 2500 3750 5000 6250 7500 8725+
F 60 60 55 55 50 50 45 45
2F 60 60 55 50 50 45 45 40

These jets in most cases go up incrementally 5 points…I have seen some odd in-between sizes 138’s 132’s ect.

(+/-) 5 points would be fine tuning from these points.

JohnnyC · 03-28-08, 12:43 PM

DCOE style carbs: (side draft) i have only see one cruiser this way...but...a good sight regardless:

Tuning your DCOE-Style Carburetor

JohnnyC · 03-28-08, 12:44 PM

taken from: Weber Carburetors Carbs 40 DCOE 45 DCOE 32/36 32/34 Jeep. Top-End Performance 818 764-1901

32/36 DGV, DGEV, DFV and DFEV
These carbs have fixed venturis so the choke size is not an issue. The pump jets are also not a problem. Do not mess with them. If you have a flat spot or hesitation when you first take off then it is likely that the idle circuit is too lean. If you know you have the idle circuit right then the primary main jet is too small. Increase the main jet size 2 steps at a time. (150 main is a 1.5mm hole...Main jets are in steps of 5. eg: 150, 155,160,etc.) Keep checking the plugs after driving it for a few minutes (Do not let it idle when checking the spark plug color for the main jets. Drive the car above 2000-3000 RPM for a few minutes then shut the engine off before letting it idle then check the plugs. If the car then transitions fine but hesitates or falls on it face when the secondary is opened you need to work on the Secondary main jet....
A good option to playing around with your 32/36 Weber jetting is to just get one of our Custom Performance Jetting Kits....We offer these for all Single 32/36 DGV and DGEV applications operating from Sea Level to approx 4000 Ft...Above 4000 Ft you start having more altitude problems and the vehicle needs to be tuned as outlined here. Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...

38/38 DGES
These carbs have fixed venturis so the choke size is not an issue. The pump jets are also not a problem. Do not mess with them. If you have a flat spot or hesitation when you firts take off then it is likely that the idle circuit is too lean. If you know you have the idle circuit right then the main jet is too small....Increase the main jet size 2 steps at a time. (150 main is a 1.5mm hole...Main jets are in steps of 5. eg: 150, 155,160,etc.) Keep checking the plugs after driving it for a few minutes (Do not let it idle when checking the spark plug color for the main jets. Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...

JohnnyC · 03-28-08, 12:45 PM

good weber adjustment site for samies:

Adjusting a Weber

and good adjustment site here:
Weber Carburetors Carbs 40 DCOE 45 DCOE 32/36 32/34 Jeep. Top-End Performance 818 764-1901

JohnnyC · 03-28-08, 12:47 PM

weber jets:
Weber Carburetors, Jets, Components APT Advanced Performance Technology Mini Cooper Parts

JohnnyC · 03-28-08, 12:54 PM

from here on tech mud:

MAF Technical Info

mphtower.com - Weber DGAV Conversion

go to tech info:
REDLINE - Serving the U.S., Canada, Central and South America for over 30 years!

JohnnyC · 03-28-08, 12:58 PM

remember OEM is the best carb IMHO

...for these rigs...but...if your already into it and/or have already got one of these on your rig...this info might help

Poser · 03-28-08, 03:04 PM

Quote:

Originally Posted by JohnnyC

remember OEM is the best carb...

That is your opinion...

Redline Weber carburetor tuning/adjusting information can be found

HERE <---- this is a link

And for those of you who like to own books, here are a couple that I have found helpful when working on these carburetors:

Weber Carburetors, HP books <---- this is a link

Haynes Weber Carburetor Manual <---- this is a link

tyama · 03-28-08, 09:25 PM

Here's a question for you guys who've got a bit of experience:

I'm running a weber 38 on my 2f. When I start it cold, the choke kicks in and it revs up pretty well. When I hit the gas to kick the choke down (off?), it starts to stumble a bit and will sometimes slow down till the engine cuts off. It didn't do this when i first installed it (about 9 yrs ago). Once it's warm, it does fine. Any thoughts? Thanks, ty

Poser · 03-28-08, 10:26 PM

When it starts acting up like that, spray some ether, or carburetor cleaner around the adapters and mounting flange for the carburetor, and report back as to what happens.

I am betting that you have a vacuum leak, that when the engine is cold it is more pronounced and when the engine is warmed up, the leak is not as severe due to things expanding as they get heat into them.

The bolts shipped with the adapter, that attach the top adapter plate to the lower plate are too long, and if not shortened up before installing, will pass through the lower adapter that they thread into, and cause the lower adapter to be pried up off the intake, creating at the very least a vacuum leak, and more likely than not, fracturing the lower adapter plate. This has been the case since the very first Weber I installed on my junk back in 1992, and is something that I have addressed with every Weber I have installed since. (At least 25, the most recent being last spring, and the bolts are still too long)

Post up what you find out...

JohnnyC · 03-29-08, 02:14 PM

32/36 adjustment

JohnnyC · 03-29-08, 02:19 PM

38 dgas adjustment

JohnnyC · 03-29-08, 02:21 PM

weber trouble shooting

JohnnyC · 03-29-08, 02:23 PM

weber carb trouble shooting

JohnnyC · 03-30-08, 11:56 AM

I am now fine tunning my rig.

I just replaced the main jets...running really well ( for those that dont know me i just put a 60K mile engine in with a redone head) stock weber was set for 155 mains I went to 142 (i had a set laying around) I am at sea level. I was running 135 for my 430,000 mile engine before replacing it.

the mixture screws are exactly (edit:just under) 1/2 turn off baseline...which is one turn...so to full in i am out 1 1/2 turns ....just right

I was running 10mpg with the 155's ....now with the 142's If I dont like the fuel economy...i can tweak it just a bit more and put a larger air correction jet...i have in now 180...i will go to 185....we'll see how it goes

3doghouse · 04-01-08, 09:21 PM

Johnny,

What size idle jets are you running?

JohnnyC · 04-02-08, 12:39 AM

Quote:

Originally Posted by 3doghouse

Johnny,

What size idle jets are you running?

i am running 60

BC40 · 04-02-08, 11:29 AM

Don't know if it will be useful information to others, but I run a 32DIR progressive openning manual choke carb on my truck. I adapted it to the F engine since I had a box of them from my Renault parts cars, and the single barrel carter that was on there was seized.

When my truck was otherwise stock and settings quite lean I managed about 16MPG with the 32DIR. Now after tuning for acceptable power, bigger tires, large roof rack, I rarely get better than 12-13MPG. I live at sea level.

Jets:

venturis: 23/24
idle jet: 55/60
main jet: 135/137
Air corrector: 180/170
Emulsion tube: f20/f6
Aux venturis: 3.5/4.5
Accel. pump jet: 50

As I mentioned the carb has a manual choke and a fuel cut off solenoid. The carb is probably too small but so far I have about 45k miles on it and am not really dissapointed.

When I was setting the carb up there wasn't a lot of baseline setting info around so I had the top off the 32DIR many,many times. A larger main works better for power at sea level but is very sensitive to elevation changes. We'll see how far off it is when I swap in the 2F before summer.

tyama · 04-18-08, 09:52 PM

Sorry for the loong delay in getting back. I did the test and the only thing that happened was a small slow down in rpm-prob because the ether cooled the carb down. I adjusted the fast idle and it seems to be good now. Thanks for all the input, ty

Quazii · 04-19-08, 06:47 AM

Quote:

Originally Posted by tyama

Sorry for the loong delay in getting back. I did the test and the only thing that happened was a small slow down in rpm-prob because the ether cooled the carb down. I adjusted the fast idle and it seems to be good now. Thanks for all the input, ty

Negative. When spraying the ether, any change in RPM indicates a vacuum leak at the point you are spraying. Th e vacuum leak is pulling the ether into the intake system where it blends with the air/fuel mixture thus changing engine RPM.

Chris

tyama · 04-23-08, 09:04 PM

Wow, Sounds like I need to put in some smaller bolts on the carb. What size works? Just cut off 1/4"? Also, what gaskets work well when I replace them? Any tips on where the gaskets should be placed. IIRC, the original ones were thin paper and went between all the metal spacers. Thanks! ty

tyama · 04-24-08, 09:54 PM

One more question...does anyone ever put sealant/silicone on the gaskets? Thanks much, ty

JohnnyC · 04-25-08, 04:32 AM

Quote:

Originally Posted by tyama

One more question...does anyone ever put sealant/silicone on the gaskets? Thanks much, ty

i have put ultra-copper on the base gaskets before....but...only when i had no choice...like if its got a rip or a large enough scratch thru it.

on the carb gaskets i normally use white litheum grease...an old trucker trick i guess you can say...to help seal an old dry carb gasket.

JohnnyC · 04-25-08, 04:41 AM

Quote:

Originally Posted by tyama

Wow, Sounds like I need to put in some smaller bolts on the carb. What size works? Just cut off 1/4"? Also, what gaskets work well when I replace them? Any tips on where the gaskets should be placed. IIRC, the original ones were thin paper and went between all the metal spacers. Thanks! ty

a 1/4 " is a bit much....just a 1/16 to 1/8 should be fine..

replacement gaskets work well when replacing them

you can alwyas get at most Auto stores...a base gasket from a Holley 5200 (a weber copy carb) (then cut out the center like a weber gasket) .........or................just get a roll of paper gasket material....also from any auto parts store....and cut out you own...and your will have extras then

all gaskets should and will go between any two metal surface...so between each manifold plates...and between the base of carb and plate and also between the intake manifold and plate...there are three base gaskets in total.