AVS2 upgrade
- Thread starter brandvdub
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The idle mixture screws are all you can adjust on those as far as mixture (rich/lean) Other adjustments are made by metering rod springs, metering rods, and jet changes. I have read that AVS2's are kind of noted for having incorrect float level adjustments which can cause rich/ bleed over issues. They are pretty finicky about fuel pressure as well. (I prefer 4#)
66 Monaco 500 365
Member
Maybe your vacuum advance was on a full time vacuum port and now it is on a timed port, making the idle timing lower that it was, causing it to have less idle torque.
My $.02
My $.02
Did you plug up the rear vacuum port, if it's not being used? I forgot to do that once, not paying attention to what I was doing, and you can definitely hear it, and it will run terrible.
On a more general note, don't expect the carb to be tuned optimally for your engine out of the box. My 77 NYB w/ stock 440 has an AVS2 that was installed by the previous owner. The secondary flap was so loose it would open just blipping the throttle (which it definitely should not do). The effect on the road was when you'd tromp on the pedal it would bog terribly. I also had to install much leaner rods in the primary and smaller jets in the secondary.
This was not seat-of-the-pants tuning. I used a tailpipe wideband O2 sensor, so I was able to dial it in pretty good.
On a more general note, don't expect the carb to be tuned optimally for your engine out of the box. My 77 NYB w/ stock 440 has an AVS2 that was installed by the previous owner. The secondary flap was so loose it would open just blipping the throttle (which it definitely should not do). The effect on the road was when you'd tromp on the pedal it would bog terribly. I also had to install much leaner rods in the primary and smaller jets in the secondary.
This was not seat-of-the-pants tuning. I used a tailpipe wideband O2 sensor, so I was able to dial it in pretty good.
Agree on the fuel pressure issue. I find they are quite sensitive to pressure and the new pumps are all over the place in pressure compared to specs. I purchased a stock spec'd Carter fuel pump and was having fuel at the bottom of the intake manifold after shut down. A gauge indicated i was getting 5 plus PSI, maybe 6, when I think the AVS2 is 4 or lower.
My friend had bleeding over issues on hos 440 so he bought a new pump from the local Car Quest. It was worse with just a tick over 10#. Crazy!
AVS2 calls for 4-5 psi minimum (it's wierd that they'd indicate the minimum as a range), 6.5 max. And I agree, the fuel pump that was on my car when I got it was pushing 7 psi sometimes.
Make sure you follow the install guide and also download the tuning guide for this carb from Edelbrock.
Make sure you follow the install guide and also download the tuning guide for this carb from Edelbrock.
You have a fuel pressure gauge, yes?
carb cheater setup? or just a wideband O2 sensor only?
It's a hand-held unit. The cables are just long enough that I can have the sensor in the left tailpipe and run the cable in through the back window. It's a bit pricey but it was a good investment imo because I have several cars that need to be tuned. I know experienced people can get good results with their eyes, ears and butts, but for myself I like being able to verify rich/lean/just right.
You and me both. When I get my exhaust overhauled I'm going to ask the shop to install a bung for an O2 sensor; some people can just tune it by ear but I like to increase the precision with the tools we have at our disposal now.
As @WissaMan mentioned, confirm you don't have any open ports that would cause a vacuum leak. My AVS2 800 cfm ran fine out of the box but it did idle rich, an easy fix with a vacuum gauge.
What is your idle RPM when in Park? Is it so low that when you put it in drive it kills the engine?
What is your idle RPM when in Park? Is it so low that when you put it in drive it kills the engine?
Fury1969WI
Member
I recently installed AVS2 800 CFM on my warmed over 440 and like @WissaMan said in their reply i had to lean it out considerably. I have a wideband O2 sensor installed and while it started and ran great it was super rich (even with an open air cleaner). Anyway, that's just tuning. Your carb should start and run out of the box - period (assuming the car was working well before the change). This leads me to ask; "why did you replace your carb?"
Also, someone (Mark Twain?!?) once said; "90% of carburetor problems are electrical!"
Also, someone (Mark Twain?!?) once said; "90% of carburetor problems are electrical!"
So true!
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