Author Topic: AFB /AVS Tuning  (Read 4638 times)

Offline Chryco Psycho

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AFB /AVS Tuning
« on: November 15, 2003 - 01:16:07 pm »
These are very simple carbs to work on but actual tuning is made difficult by the lack of tuning parts available for them.  The Edelbrock carbs are very similar & use the same parts for tuning though

Step1 - Check the float level , this requires removal of the top of the carb , once removed invert the top & use a drill bit to check the distance between the top of the float at the end away from the pivot & the body with the gasket in place , Most AFB & AVS Carbs use a 7/32 float setting, the 383 avs seem to use 5/16 instead , with the EDDYS there should be a spec in the manual with the carb  > this should be checked even with new carbs as they can bend during shipping , bend the tab that touches the bootm of needle to adjust the settings. While you have the top off also set the float drop , this is the measurement from the top of the float to the body when the top is the right way up , there is a tab behind the needle that can be bent to adjust the drop , the spec for drop is 1/2".

Step 2 - reassemble the carb get the engine running & warm , make sure the dist vacuum hose is connected to the port 1/3of the way up the carb on the right side of the front of the carb ,adjust the mixture screws & get the car running as good as possible now take a manifold vacuum reading,  at idle , in gear if it is an automatic tranny, [you can remove the cap above the metering rod & watch to see if the rod stays in the down position at idle ] there is a spring under the metering rod which will need to be changed if the rods do not stay down at idle , springs are available in 3,4,5,7or8" increments & you need to uise a spring at least 1" below the vacuum reading you get.

Step 3 - adjust the jetting, take the car for a drive at a steady cruise & resonable speed 30 mph + for 5-10 miles & using a new spark plug check the color you want tan -orange color  if it is Chocolate or darker you want to down jet,  if it is light orange to white you need to upjet . This not as easy as it seems , you need to remove the top of the carb & change both the jets & metering rods to move one step at a time , you will need the chart & the tuning kit part#1480  [Hopefully someone can scan the chart for us , hint hint] I have commonly found the Eddy carbs to run lean even with the biggest available jets installed , you may need to drill them with # bits to get enough flow I have also modified & made metering rods to try to get both steps correct [up position & down position]

Step 4 - Floor the car a dead stop upto the speed limit shut off & check the plug color again if it is darker or lighter adjust the rear jets the same way as the front jets

Step 5 - adjust the accelerater pump arm , by adjusting the rod away from the body you decrease the amount of fuel delivered , you want as little fuel delivered as possible  without creating a bog. if it bogs immediatly move closer to the body again, there are only 2 holes or sometimes 3 depending on the model of carb you have so you cannot adjust it much.
If it bogs 1/2 a second after the throttle is floored you will need a larger squirter which can be a problem I have not been able to get new ones of different sizes  but you can drill them with # drills & if you go too big you will need to solder the tube & redrill. You wil have to remove the top of the carb to get at the squirter

Step 6 - for maximum performance you need to adjust the rear air door ,on the AVS this is esay , you can undo the outer lock screw & adjust the center screw 1/4 turna at a time counterclockwise until you can feel the secondaries bog as the air door opens  then tighten the screw 1/4 turns until no bog can be felt. With the AFB this is much more difficult, you need to remove the top of the carb again & remove the rear boosters & remove the air door , at the bottom of the weights you need to drill 2 holes [1 each side] & try the carb out if no bog is felt you can make a second hole 1 side at a time , or enlarge the first hole now you can either play chicken & say to yourself , it is better I quit or keep going until a bog is felt , at which point you either need to weld a hole back in or tap the hole & put a screw in to add weight again , my experience is that you can drill 2 3/16" holes in virtually any application & not bog after that it will depend how much converter & gear etc you have as to how much more can safely be removed    
 
 

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Offline BIG MIKE

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Re:AFB /AVS Tuning
« Reply #1 on: November 15, 2003 - 10:43:01 pm »
i have AFB rejet kit i'll post a picture tomorrow if my net connection lets me, i've been having trouble so i'll post as soon as i can.

i'll have it monday,
« Last Edit: November 16, 2003 - 07:57:49 pm by BIG MIKE »

Offline BIG MIKE

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Re:AFB /AVS Tuning
« Reply #2 on: November 17, 2003 - 10:51:23 pm »
here is the jet sizes i'll look more.

[attachment deleted by admin]

Offline BIG MIKE

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Re:AFB /AVS Tuning
« Reply #3 on: November 17, 2003 - 10:53:09 pm »
top

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« Last Edit: November 17, 2003 - 10:53:29 pm by BIG MIKE »

Offline Chryco Psycho

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Re:AFB /AVS Tuning
« Reply #4 on: November 18, 2003 - 12:16:08 am »
I am looking for the actual tuning guide from the edelbrock carb book Still if someone has it

Challenger - You`ll wish You Hadn`t

Offline BIG MIKE

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Re:AFB /AVS Tuning
« Reply #5 on: November 18, 2003 - 12:20:45 am »
i think i got it(came with carb) but this was all i could find today  

Offline BIG MIKE

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Re:AFB /AVS Tuning
« Reply #6 on: November 19, 2003 - 10:12:41 pm »
i'm still looking, i would have bet that it was in my tool box with the carb. gasket

Offline Chryco Psycho

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Re: AFB /AVS Tuning
« Reply #7 on: June 23, 2014 - 01:11:18 pm »
too bad the pix were deleted  :banghead:

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Offline Racer57

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Re: AFB /AVS Tuning
« Reply #8 on: June 23, 2014 - 01:36:10 pm »
too bad the pix were deleted  :banghead:

11 year old thread. WTF you expect ?  :D

Glad its here. I'm needing to do some find tuning to mine.

This winter I installed a new Eldebrock intake and 650 AVS carb on my 383. Its had a surging problem and I found that the metal plate that Eldebrock supplies with the carb to block off vacuum ports on the bottom of the carb had a slight warp to it and that's where the leak was at.  :pullinghair: