Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ Adjusting Dual Webers

Posted by: black914 Mar 14 2005, 06:20 PM

I purchased a 75 2.0 liter this past November and have been working on the electrical gremlins. They are now all corrected and I am now concentrating on the mechanicals. My question concerns adjusting dual webers (40IDF's). The previous owner converted from fuel injection but I have no information on how to correctly adjust the carbs. I am getting occasional backfire through the carbs during normal driving conditions. Is there any book I can purchase that will give me a good outline of how to correctly adjust the carbs? Can anyone refer me to a tech article that will help?

Posted by: MarkV Mar 14 2005, 06:38 PM

Try this one: http://www.aircooled.net/gnrlsite/resource/articles/dualcarb.htm

Posted by: ws91420 Mar 14 2005, 06:49 PM

Buy a synch tool for air flow best money I have spent on a tool for my car so far.

Posted by: black914 Mar 14 2005, 06:52 PM

Thanks for the reply MarkV-I will check out the article.

Posted by: black914 Mar 14 2005, 06:54 PM

Thanks Welby for the advice! I have been tracking a synchrommeter on E-bay...do they supply sufficient user instructions when you purchase one?

Posted by: ws91420 Mar 14 2005, 07:07 PM

No major instructions with it. Used tech articles from the bird board about its use and instruction w/ the carbs I installed. Basically you want the air flow to be the same in all barrels. Then make idle adjustments and recheck the flow. This is what mine looks like and I think the one of the better versions out there.

Posted by: ws91420 Mar 14 2005, 07:07 PM

Hit wrong button

Attached image(s)

Posted by: jwalters Mar 14 2005, 07:22 PM

Do it all: adj timing, idle, balance, and repeat at least 3 times to get it all dialed in right-
Make sure your valve lashes are correct--very important.

Posted by: trekkor Mar 14 2005, 07:28 PM

This is a real raw, "get it close" method.

Disconnect the linkage between the carbs.

Turn in the idle and air by-pass screws all the way.

Back out the idle screw 1 1/2 to 2 turns.

Start the motor and get an idle rpm speed of 1k.

Using the sync tool to check the flow of each hole. Note which one draws the most. Call that baseline.

Adjust the airflow to the baseline cylinder's CFM by backing out the air bypass screw on each of the lower pulling ones.

As the idle creeps up, keep it down to 1k by adjusting the idle speed screws on the shafts the linkage attaches too.

Blip the throttle between adjustments to "clear" the carbs. Go around and adust the remaining barrels to the baseline cylinder.

Tighten up the jam nuts on the air by-pass screws and reconnect the linkage. If the idle speed increases when the linkage is clipped on, it needs to be adjusted so it is not binding.

Now double check that all cylinders are pulling the same CFM at idle. If not, keep trying, if so, drive it!

Hope that helps.

KT

Attached image(s)

Posted by: black914 Mar 14 2005, 07:47 PM

Thanks, Trekkor, for the info! That is what I was looking for! When you purchase a car with no manuals, etc. you have to begin researching somewhere. That is the great value of this 914Club! I will use this info along with all the useful tidbits I have received and begin attacking the tune up this weekend, weather permitting!

Posted by: Joe Ricard Mar 14 2005, 07:56 PM

It is just my opinion but I do proclaim victory on my carbs.
DON"T TOUCH THE BY PASS SCREWS
they should all be closed snug. If the carbs won't balance out, it is because of another problem. Most likely valve lash. or a jammied up plug wire.
Everything else Trekkor said is pretty good. Now you got to figure out which one of us is full of shit.

Posted by: trekkor Mar 14 2005, 08:04 PM

QUOTE
DON"T TOUCH THE BY PASS SCREWS

They have to be for something...

Seriously, it doesn't take much to change the CFM with a 1/4 turn of the ABP screw.

KT

BTW, if the car still doesn't come round, then the jets could be wrong, and that's part of the advanced "Weber Dance" I never learned.

Posted by: jwalters Mar 14 2005, 08:58 PM

Go to aircooled.net and look at the tech articles--explained in detail...

Posted by: tat2dphreak Mar 15 2005, 09:10 AM

great step-by step trekkor!! you rock!

Posted by: morphenspectra Mar 15 2005, 10:06 AM

best money you will ever spend when it comes to understanding webers.
james
appearance & perfomance

Attached thumbnail(s)