cagotzmann

I am looking at doing a final tune for my GM ZZ383.
Carb is a 770 Street Avenger on a 7516 Air GAP.
Its running rich at WOT 10.1 - 11.2 which I believe smaller jets will bring this back in line. The strange thing is with throttle response.
Slow throttle accel works fine, quick throttle the afr goes 19+ a very quick spike then down to 10.1 - 11.2.
What adjustments will bring the AFR spike down to better numbers ?

76CSRvette

does the car bog or jerk when it spike or drops. is it drag racing or street conditions. sorry I cant help but im looking into getting a/f gauge meter. Did you make your own or buy a set or is it a hand held device.

dugsgms74

If the spike isnt accompanied by a bog or ping I wouldnt worry about it, it takes a bit of time for the fuel from the accelerator pump to catch up to the sudden rush of air. Also, be careful with the AFRs posted on the internet, most of those are for EFI vehicles and carbs need to be a bit richer due to the fuel not being as well atomized.

cagotzmann

It bog's and sometimes sounds like a miss / backfire.

cagotzmann

http://www.zeitronix.com/ connected to my laptop only. No displays.

CanadaGrant

You probably have to come down on the jetting with that big a carb. I went small and used an Edelbrock 650cfm thunder series on my wife's ZZ4 crate motor and it worked perfect right out of the box. I have the GM "hot cam" and am using 1:6/1 rollers. I always found that going with a big carb caused me more problems than it was worth.

Günther-C3

Did you adjust the acceleratorpump correctly?

dugsgms74

Hmm, youll need to make sure that youre getting accelerator pump squirt as soon as the throttle blades start to open. If not, youll need to adjust/bend accelerator pump linkage to get that to happen.

Haggisbash

JMPO I'm no carb guru but I would suggest going down two sizes on the secondary main jets first and see what your WOT is before tackling the acceleration problem. You may need to do this to the primaries as well. Usual procedure is to change jets two sizes at a time and then once you have established when you have gone too far you can go back one size.
Best to tackle one problem at a time. How is your timing advance curve? Too quick a curve can cause the problem you describe when accelerating. Check the accel pump is working properly as dugsgms74 says. Next option may be to change the accelerator pump cam to give a quicker shot or you may have to put a larger squirter in the accel pump. Best thing is you have the A/F gauge to quickly see what changes make and best of all you can check things out on the road in real load conditions.

chevymans 77

can you post the list # so we can look up the OEM setup for this carb.

These carbs have an inherent bog issue and with some minor adjustments should be able to resolve them.

Start with the accelerator pump slack, work with the pump cam. Sometime the pump arm is in a position that it is not riding on the cam but on the spring. Working with the pump cam may resolve the slack in the pump arm.

Neal

cagotzmann

Holley street avenger 83770

garygnu

you could drill out your air bleeds ,001 at a time until you reach a better AFR .I have a race demon carb ,and make my own screw in air bleeds.I also have a AFR gauge .

dugsgms74

I think Neal is on the right track here, very common with these carbs.

bluedawg

I hear this slot about the steer avenger series.

oops!

F22

Good timing on this article and I'm glad to see the comments,.as.I'm getting my motor back next week and have the AFR gauge, brand new in the box. Hope the OP can fix the bog. I agree with the accelerator pump adjustment and thinking it might be a combination of when the secondaries open up. Is it possible, that the acc. pump is squirting the fuel into thd carb, before the secondaries are opening up? Or is the pump, not the problem and the OP has the lightest spring in the carb and it's opening up too soon? Just thinking out loud. Unless I missed it, it'd be nice to know what spring is in there.

Haggisbash

Holley tend to put in a heavy spring out of the box because they don't know how heavy the vehicle the carb will be fitted to will be. At least that is what they used to do. Its easy to check if the secondary is opening fully.

Danish Shark

What gauge did you get?
I'm looking at this one:
http://www.summitracing.com/parts/inn-3822

I've been looking for pictures of cars that had the clock replaced with an AFR gauge, but the threads I've found are so old that the pictures have been deleted.
Any experience with a built-in gauge in the center gauge console?

cagotzmann

http://www.zeitronix.com/

connected to my laptop only for data logging. No displays.

cagotzmann

Running altitude is at 2200ft.

I currently have the yellow spring for the vaccum secondaries.
Stock jets 70 / 75 and a 31 Discharge nozzle.

Just changed to 67 / 72 and a 35 discharge nozzle. (testing later today to see results)

The problems I have is during quick throttle open I get a lean spike 18-20 AFR then I get a very rich afr during accelleration 10.1 - 11.2 approx.

F22

I didn't get the Innovate, as the reviews.indicated, because the O2 sensor needed calibrating, periodically, versus the AFR, which uses a more expensive, Bosch sensor. I haven't mounted.mine yet. I have the external gauge housing for now, and a vacuum meter, where the clock used to be.