More AVS/AFB Rod Questions

[Macdon221]

Good Day All,

So more AVS questions.....

Dismantled a Carter 4618S yesterday from a 440 car. Engine has a small cam, a little porting, standard intake manifold. Runs very well. Engine was rebuilt very recently.

The primary jets are the Standard 120-501 (.101) and the Secondary's are 120-395 (.095).

The metering rods are not standard. The Standard rod that would of come stock in this application is 3 step 16-545 (.065x .062 x .055). The Rods that are in the carb are 2 step carter rods that are 16-6640 (.066 x .040) that I believe came from a Carter 10-205 strip kit for AFB carbs. The rod is the exact same overall length.

Is this an acceptable set up?

In the carter 10- 202 AVS Strip kit is looks like the Skinniest rod at WOT in that kit is the 16-404 (.063x.060x.051)

Is that big difference between the .040 and the .051 at WOT.

Any comments on this set up at all?

Any info appreciated.

 

[gtxrt]

going from 51 to 40 is about 8%-9% more fuel. I would be reading the plugs to see what is going on.

 

[Dave6T4]

I think that 16-404 would a lot closer than the rods you found in the AVS. They look to be 1 or 2 steps richer than factory. Did the Strip Kit come with the booklet that shows rich/lean mapping? It is a great guide to playing with rods and jets. That .011" difference in WOT step would make it way rich. Does the carb still have its original size primary jets? I haven't worked on an AVS in quite a while. I have Edelbrock 750 cfm's on both my stockish 440's. I have found they work best with one step leaner (fatter) metering rods with 1 step lighter (yellow) springs under them. I bump the secondary jets up one step larger.

 

[Macdon221]

Yes....I have a 16-404 Rod.

No...I don't have a mapping book/diagram for the AVS Strip kit. Is there one out there to be viewed?
I have seen the ones from the Edelbrock carbs. I would like to see if there is one for the AVS. Anyone know?

GTXRT....being a nerd...yes I did the area math and came up with an exactly 10% difference between a 51 and a 40 at WOT. Being new at this I may be wrong. But pretty close to your 8-9%.

Yes factory primaries and secondary's I have them listed above.

 

[gtxrt]

Yes....I have a 16-404 Rod.

No...I don't have a mapping book/diagram for the AVS Strip kit. Is there one out there to be viewed?
I have seen the ones from the Edelbrock carbs. I would like to see if there is one for the AVS. Anyone know?

GTXRT....being a nerd...yes I did the area math and came up with an exactly 10% difference between a 51 and a 40 at WOT. Being new at this I may be wrong. But pretty close to your 8-9%.

Yes factory primaries and secondary's I have them listed above.

i used the edelbrock tuning chart for the 750 cfm carb to get the %

 

[lewtot184]

I use 16-575 rods, stock step- spring, and .1025 primary jets up front and .098 jets in back with my 4618. Drives very nice with stock cam, intake and ex̌haust.

 

[Geoff 2]

The 66/40 is probably an Edel rod & 2 step, not 3 step as reqd for the AVS. I have a pretty comprehensive list of AVS jets/jetting, & the smallest power step used was 0.053". A long way from 0.040"......

 

[RJRENTON]

GTXRT....being a nerd...yes I did the area math and came up with an exactly 10% difference between a 51 and a 40 at WOT. Being new at this I may be wrong. But pretty close to your 8-9%.

YES.....AREA CALCULATIONS (jet bore size vs rod diameter) ARE THE ONLY TRUE WAY TO DETERMINE CORRECT fuel flow.....most "experts" are not aware or how to calculate or correlate the jet/rod relationship......
BOB RENTON

 

[TorRed]

Watching with great interest, this is mostly voodoo black magic to me!

 

[Dave6T4]

16-162 = .0650 / .0620 / .0580
16-165 = .0635 / .0600 / .0550
16-404 = .0635 / .0600 / .0510
16-164 = .0630 / .0600 / .0530
16-475 = .0625 / .0590 / .0500
16-216 = .0625 / .0580 / .0470
16-217 = .0620 / .0580 / .0550

AVS that use these 3-step rods have taller primary jets than Edelbrock and AFB that use 2-step rods. Carbs that use 3-step rods can be externally identified by metering rod covers that have "bump". AVS started production on 1968 Mopars, but 4326/4327 AFB on 1967 440 Magnum also used 3-step rod.

 

[RJRENTON]

16-162 = .0650 / .0620 / .0580
16-165 = .0635 / .0600 / .0550
16-404 = .0635 / .0600 / .0510
16-164 = .0630 / .0600 / .0530
16-475 = .0625 / .0590 / .0500
16-216 = .0625 / .0580 / .0470
16-217 = .0620 / .0580 / .0550

AVS that use these 3-step rods have taller primary jets than Edelbrock and AFB that use 2-step rods. Carbs that use 3-step rods can be externally identified by metering rod covers that have "bump". AVS started production on 1968 Mopars, but 4326/4327 AFB on 1967 440 Magnum also used 3-step rod.

I'm aware of the rod diameter/step list. I have the same list plus a10-12 additional sizes. The three step rods were used on the 273/ 235 HP engine (Carter #3895S and others) and when used with the appropriate step up pistons (and subsequent springs and cover plates to achieve the desired response). I was referring to the CORRELATION between the ACTUAL OR PRESENTED AREA OF THE JET, WHEN THE CORRESPONDING ROD DIAMETER IS IN THE JET. REMEMBER: Actual AREA determines the fuel flow, either in pounds/hr or grams/second, or some quantifiable unit of measure. IT IS NOT TOTALLY A DIAMETER vs DIAMETER calculation but area differences......Personally, I prefer the three (3) step rods (combined with the corresponding appropriate hardware) as it provides a "smoother" fuel transfer.....
BOB RENTON

 

[Geoff 2]

Bob R,
Your exactly 10% in post #8 is exactly wrong. The correct number is 12.3%. Maybe not as 'expert' as you think you are.....

 

[Rebelrouser]

I think you are overthinking the carb. Bottom line is does it run like you want? One thing to think about is we don't have the same fuel as we did in 1968. If you are running pump gas the alcohol content will require a little richer setting. And remember they don't formulate fuel for carbs anymore, the formulate it for high pressure fuel injection systems. Reed vapor pressure or how the fuel evaporates is different today as well. But I have always been one to modify this or that to get the desired results.

 

[gtxrt]

like i said in my post check your spark plugs.

 

[Some Car Guy]

The 575 rod in my 440 avs was on the rich side. It runs noticeably better in cool weather. The stock size rods or at least those specs on the power step are pretty close. I’m still trying to find a set a little leaner to try. Best so far has been leaner cruise and stock power.

 

[Geoff 2]

The 574 rod is 0.002" leaner on the power step.