Carter AVS jets questions

[Macdon221]

A few questions about Carter AVS jets....

The primary jets in my carb are listed as 120-501 (0.101)....in the CARTER parts book listed as "Tall Jets".....what is the compatibility for these jets? Do you "need" the tall jet for the 3 step rods?

Can you use just a "regular" 0.101 jet (120-401) if you can't get the "Tall Jets"? If anyone can clear this up for me that would be great!

Also some of the jets in the manual have a symbol by them coded as "burnished type jets". I know what burnished means...but what's the difference in the jets?

Been looking for a 16-545 (.065x.062x.055) step-up rod is anyone has one!

Hopefully I can figure this out!

Thanks

 

[AR67GTX]

Dragon Slayer is a far better authority but to the best of my knowledge you can use standard 2-step jets and rods. You need the flat piston covers in lieu of the domed ones and I believe (?) you need to use 2-step pistons and springs also. I think the 3-step give you a little better response on the primary system but it’s probably not something that makes much difference in everyday driving.

 

[Macdon221]

Thanks

Can you use the "low regular jets" with the 3 step rods in the primaries?

 

[AR67GTX]

Yes, you can physically run it that way, but you lose all Carter calibration of the transition and primary circuit and only Johnny Carson as the great Swami would have had any idea how it will run - possibly OK, but also very possibly not for the better. It might struggle to go rich enough with the accelerator floored (vacuum low). I don’t know if the rod will rise enough to sufficiently richen the fuel flow with the small tip section.

I checked and you will need 2-step pistons to switch to standard jets and 2-step rods from 3 step. The 2 step Carter parts are basically interchangeable with Edelbrock parts and not expensive. I believe Mike’s Carb Shop has all of it and they can probably recommend a 2 step jet and rod system that will work well to replace the 3-step parts.

 

[Macdon221]

I want to keep the original 3 step.

I have tall primaries. I was just trying to understand the reasoning. Thanks for the explanation.

Any idea on what the “burnished” means?

 

[Geoff 2]

No, you cannot use the 3 step rods [ that were used with 'tall' pri jets ] with the shorter jets. The metering steps on the rods will be in the wrong position.

If you want to keep the 3 step rods, you have to use the taller jets.

 

[AR67GTX]

I haven’t noticed the term “burnished” before on jet descriptions. Other than the obvious surface treatment I don’t know what the significance of that would be other than to smooth the transitions for more uniform fuel flow.

 

[Macdon221]

https://www.carburetor-parts.com/assets/manuals/carterjetcoversion.pdf

Look at the tiny "Cross Symbol" next to some of the jet listings and the code at the bottom.

 

[oldkimmer]

Thanks

Can you use the "low regular jets" with the 3 step rods in the primaries?

No, u need 2 step rods and covers with the low jets. 3 step rods is the tall jets and raised covers. It will run by mixing and matching but how good is anybody’s guess. Kim

 

[lewtot184]

You can use 3 step rods with short jets but you must use the flat edelbrock cap that covers the step- up piston. This puts the rod and jet into a more proper relationship.

 

[Geoff 2]

^^^^ Completely wrong. Read post #6.

 

[lewtot184]

^^^^ Completely wrong. Read post #6.

It's obvious you've never done this before.

 

[AR67GTX]

https://www.carburetor-parts.com/assets/manuals/carterjetcoversion.pdf

Look at the tiny "Cross Symbol" next to some of the jet listings and the code at the bottom.

My only wild guess would be that they have taken a smaller jet and taken it to the next size up by burnishing/polishing, rather than drilling or reaming. Burnishing is akin to polishing so I would think a burnished jet, assuming the polishing is in the throat and the orfice might very slightly increase flow. Otherwise I don’t understand the significance(?).

 

[Macdon221]

Thanks for everyone's reply!

 

[Geoff 2]

Lewtot,
You are correct, I have never done it before. And nobody in their right mind has either because as I already alluded to, the metering steps on the rods do not line up with the restriction in the jets.

 

[lewtot184]

Lewtot,
You are correct, I have never done it before. And nobody in their right mind has either because as I already alluded to, the metering steps on the rods do not line up with the restriction in the jets.

I guess I'm out of my mind. The real caveat to it is not using the original long step up spring. But, in fairness to you I do prefer the factory 3 step system. On the other hand, if factory parts aren't available then edelbrock parts can be substituted; preferably using the whole edelbrock step up system.

 

[Geoff 2]

The longer spring will only cause enrichment at a lower vacuum level.....& will require more idle vacuum to fully seat the piston at idle.
The 3 step rods are about 1/16" longer than the 2 step. The tall pri jet used with the 3 step rod has the actual metering orifice 1/8" higher than the short jet.
What this means is that the WOT step might meter the fuel ok, but at cruise [ met rod all the way down ], the middle &/or cruise step of the rod will be in the metering section of the jet. Inconsistent/varying fuel delivery for cruise.

I would imagine also that the emulsion holes [ their size, number & position ] in the pri boosters would be different for 2 step & 3 step rods.
So not a good idea to mix parts.

 

[AR67GTX]

Yes, as I said, you lose the Carter calibration parameters and are off in never, never land. Of course if you have O2 sensors installed and a good laptop tuning program it might be an interesting science project.

 

[Rebelrouser]

A few questions about Carter AVS jets....

The primary jets in my carb are listed as 120-501 (0.101)....in the CARTER parts book listed as "Tall Jets".....what is the compatibility for these jets? Do you "need" the tall jet for the 3 step rods?

Can you use just a "regular" 0.101 jet (120-401) if you can't get the "Tall Jets"? If anyone can clear this up for me that would be great!

Also some of the jets in the manual have a symbol by them coded as "burnished type jets". I know what burnished means...but what's the difference in the jets?

Been looking for a 16-545 (.065x.062x.055) step-up rod is anyone has one!

Hopefully I can figure this out!

Thanks

To my knowledge the AVS uses a slightly taller jet and a rod with three steps. You can use the regular AFB style jet and the two step rods it will run just fine. Someone mentioned the better calibration of the three step rods, that might have been true with the fuel the AVS was designed to run on, but that type of gas is no longer sold at the pumps. Fuel sold today is blended with high pressure fuel injection in mind. Just use a standard AFB style jet and metering rod and tune it until it runs well. If it sits a lot don't have pump gas with alcohol in it, it may corrode the inside of the carb. Seen lots of these carbs with white fuzz inside of them, jets are usually stuck, and it is just a mess to deal with.

 

[Dragon Slayer]

Springs are not a factor 2 or 3 step rod. Mopar almost exclusively used the 61-604 step up spring. 1 1/2"+ closed coil spring. Regardless of 2 step or 3 step carb. Remember some early AFB were 3 step too.

If your trying to get the same calibration you would need to compare the rods for length and transition point locations. Not all rods are the same.

What specifically do you need on parts, I might have what you need. I do have AVS 3 step rods. Or contact me via PM.