"Super Tuning" the OEM Chrysler 4133S 575cfm Carter AFB?

I have the Carter 4133S AFB off of my '66 Coronet 383-4 barrel car due to some trash in the needle and seat. The car runs good on the idle circuit however the secondaries are lean (.083 stock jet) and I suspect the primary could be a little fatter to richen up the transition. We did have really good luck drilling out the factory squirter to .035 otherwise it's pretty much stock sans the orange metering cup springs.

The engine is a very mild .040 over 383 with 9.5:1 measured compression, replacement 383-440hp cam, stock manifolds, etc.

Anyone have a good baseline for tuning the common 575cfm AFB found on many of our muscle cars? It's hard to find parts for tuning these so I figured I'd ask if any of you guys attempted to make one run on a hotter than stock engine.

.089 primary jet
.083 secondary jet
orange metering springs
stock metering rods
.035 squirter, middle hole on pump arm
1/2" composite Edelbrock dual plane spacer for E10 garbage

As I said above it runs pretty good sans a lean spot in the transition and by the look of the plugs (checked properly) the WOT AFR is a bit lean.

Any thoughts/insight much appreciated as always.

ps I have replace the upper radiator hose and clamps lol

Can you use the rods out of an Edelbrock strip kit or do they have be the old 3 step style rods?

I have had really good luck with the three step rods but would be willing to try anything.

I still have a bunch of Carter jets, metering rods, maybe some metering rod spring kits and some squirters in my race trailer. Tell me what you need, there yours

The next heavier step up spring (possibly even heavier after testing). Move the accelerator pump rod to the rear hole. Where is the float level? Is it at the factory setting? If so I'd raise the float level about 1/8, you may be able to get away with even more depending on fuel pressure. E10 will probably require one size up in jet all the way around.
Doug

Are you sure it's lean, or is the secondary air valve opening too early?

The later JY snorkel type A/C probably fits, allows cold air @ WOT and hot air for cruise, run a duct from the snorkel to the radiator support.

I will be in touch sir! Thank you for the support as always.

Floats are set at 5/16+ on both sides, 3/4" float drop per FSM.

Accelerator pump rod is on the middle setting. I'll try to move it back to the rear hole.

I did open up the secondary jets to .086 measured with a pin guage. I was hesitant to open up the primaries before I see what parts Cab has stashed away. Thanks for the advise.

Also of note, my issue was not needle and seat but rather a sunk float.

I had considered the secondary air valve being an issue. I figured I start with jet and go from there. In my travels I did find a 4130S AFB so I do have some extra parts to try as time allows.

As absurd as it it sounds the *only* reason I am still running this old AFB is to keep that goofy little air cleaner. I have a few we could try either way thought. Thanks for the suggestions.

Are you using a wideband? If not, good luck with the plug reading.

If you are experiencing a tip in stubble you may need to go to a smaller size squirter. This seams to be opposite from what one may think but what it does is changes the deration of the squirt. The position of the rod on the accelerator pump arm controls the amount. What is happening with the large squirter is you get a big gulp of fuel then a dead spot. With the smaller one the stream of fuel last threw out the entire stroke.

I had considered the secondary air valve being an issue. I figured I start with jet and go from there. In my travels I did find a 4130S AFB so I do have some extra parts to try as time allows.

As absurd as it it sounds the *only* reason I am still running this old AFB is to keep that goofy little air cleaner. I have a few we could try either way thought. Thanks for the suggestions.{quote}



I believe a 4133 S AFB has a weighted air door, not a spring controlled air door.
Doug

You are correct, it is a weighted air door. We are headed out for a test drive, I'll check back in with some data.

At this point I have not put the wideband on it however the bungs are installed. Over the years I have worked my way into a pretty good tuning strategy with carbs that seems to work okay. It's fun to see how close we can get and then verify our results with the LM-2.

I honestly figure someone had a recipe for this common 575cfm AFB that came on many 383's and 440's.

The carb is back on and seems to run good again and is very responsive. Jake might be correct on the too big of an accelerator pump shot. I moved the arm to the inside hole and it made a rich stumble when I tested idle to WOT in the driveway. I'll put some heat in it and see what it does.

Thanks again for all of the advice!

How I stumbled on this was Dave Dudek had some modified carbs for one of his hemi's in fast and on my Dyno he had a bad stumble. He sent the carbs back to the builder and he put larger squirters in it only to make the problem worse. So I got out the old carter tuning book and read it and that is what they said to do. So I pulled the squirters out and apoxied the hole shut and then re drilled them to over half the original size and bingo it worked. I now am a believer. Hope all works out for you. Jake

Verify the fuel level in the bowls.
I have had issues where the fuel level was too low (after setting the floats to spec.) This resulted in a bad tip-in stumble.
I did the larger squirter shot, richer jets, and such which only helped a small amount.
Once I re-adjusted the floats so I have fuel in the carb bowl at least as high as the notch in the plates separating the pri/sec jets, then it ran great, but I had to undo the changes I made (larger pump shot, and larger jets.)
With the E-10, I would change to a size larger jet front and rear.
The Edelbrock parts will work in a AFB with two step rods.

All the AFB I've seen except some of the early 273 AFB, they didn't have any thing above the venturi , have weighted doors. Only the AVS and Thermoquad carbs. have the spring loaded doors
As far as having a decent tune up for todays fuel and the different altitudes and weather conditions, your probably going to need EFI to get that done

You are correct on the air door. We have a few of those kicking around too.

To catch you all up to date we sid take a 20 mile ride and it appears the tip-in hesitation is gone. The roads were wet so I'll have to wait a few weeks to test the accelerator pump and idle-WOT behavior. Once we get some positive results we can all have a laugh when I hook up the wide band.

Thank you for the heads up, I'll break out my old Carter manual and read a little while this snow storm blows in. I know what good running 383-4 feels/sounds like and this one isn't running like that...yet. IMO most enthusiasts have never road in a good running stock (or close) 383 or 440. Between the nylon cam gear, camshaft grinding errors (or not degreeing the cam), carburetor issues and ignition issues I've seen more dogs than not in these stock style rebuilds.

And to give you a visual of what we a re driving this winter:

KOOL Car I had one in high school with a 383 4bbl manual streering and manual brakes I wish I still had the car 😃😃