Already using smallest secondary rods...how to further richen quadrajet secondaries?

[Eric B]

I am running a late model 800cfm quadrajet on my 464cu Buick.


I have idle, cruise tuned exactly where I want it.


WOT power is good, but I am running at 13.2 to 13.6 A/F from 4250 to 5500 rpm. I would feel much better if I could get it down into the 12.7 range especially at the higher rpms.


I am already running the smallest secondary rods I could (CC).


What options should I pursue at this point?


Carb info:
Carb number 17057553 0507
74 main jets
50m primary rods
CC secondary rods


TA 290-94h cam
1.6 roller rockers
Edelbrock stage 1 heads
TA 1 7/8 headers
Edelbrock performer intake
Factory ram air cleaner

[analyte]

What hanger are you using? There are multiple hangers to adjust the height to which the rods are raised.

Keery

[Eric B]

The hanger...of course. I have an M in there right now. I have a few others. The chart I have shows that the earlier in the alphabet the letter, the more secondary fuel you should get (so more with B than M). I will try my H and F hangers tonight.

[Eric B]

Ok, here is where I am at.

Determined the problem was that the secondaries not opening completely....the adjustment spring was too tight. I am embarrassed to admit this....never thought to check it. I bought this carb from a company that supposedly built it custom for my specific engine.....I learned my lesson. I was trying to save some time by buying the carb I did. I have now spent so much time in this carb I would have been many hours and hundreds of dollars ahead if I had just rebuilt one and tuned it myself using cliff ruggles book as a guide.

So.......I decided to start over......used "recipe 2" as my base from the book. I still need to measure the various tubes and restriction orifices next time I am in there....but it was very late and I was pretty sure I had found the smoking gun.

Ended up with 45 primary rods (had a set of no step, full taper, long rods in my spare parts), 72 primary jets, H hanger, and AY rods. I think I may still try the 44/73 recipe that cliff suggested above, but I went with what I had on hand and used the APT to bring it in. I live at 5500 ft elevation, so the 72 may be good here. Pretty happy. Smooth off idle, good part throttle response, and 14:1 A/F at highway cruise speeds. (Keep in mind this carb was shipped to me with 76 primary jets, 47k primary rods, and CE secondary rods with a M hanger......supposedly custom built for my application)

So, all should be good, right? Well, I experienced something interesting when switching from the CC to larger secondary rods (I tried .440, .527, .567). With each larger set, while 4500-5500 rpm power improved, and I ultimately ended up with good A/F in the 12:5:1 range at WOT, I lost noticeable power in the 2000-3500 rpm at WOT. With the CC rods, even after i adjusted the secondary spring tension, I could light up the tires at a rolling 15-20mph by flooring it. Considerable power. Not any more. I kept messing with the spring tension to get the secondaries to open faster, but I would eventually experience bog and never got that lower rpm WOT throttle response. I want the lower and upper rpm WOT power.

I am open to suggestions. I think I will play with some smaller secondary rods and longer (higher alphabetical) hangers as well as spring tension so I get more fuel in initially but limit the max flow.

[Eric B]

Went back out tonight and tried to finish tuning.
I decided to stick with the 72 primary jets, 45 primary rods, CC secondary rods (.300), and the M hanger after testing tonight.

My WOT A/F at 3000 to 5500 RPM is 11.5 to 12.

I know it is richer than I want but given my available parts, that is the best I could come up with.

I actually observed that my WOT A/F got richer as I INCREASED my rod size according to final width. This had me scratching my head until i got home and read the full chart on rod size.

After looking at my full rod chart, I suspect that I observed this because of the length of hanger - the M hanger is not pulling the rods up far enough to make a proper difference given the taper of the various rods I have. At 70 deg taper, which is where I suspect they are pulling up to with the M hanger, the CC rods are actually the LARGEST at .599, even though they have the smallest final dimension. The CV is exactly opposit-smallest at 70 degrees, largest at 90 degrees full open. That would explain it.

The only other hangers I have on hand are a H and F and those cause the car to get too rich with those rods and I lose some low end response at WOT.

I am going to try one more round - maybe next week. I will order in a K hanger and DA rods and see what I can do. Ideal might be something like a CD rod with my F hanger....but not sure I can come up with those rods by next week since they are no longer produced.

Learning a lot about tuning these carbs. Having fun.

[67 455 Bird ragtop]

Have you contacted Cliff for advice?? He's usually open to advice if you give him enough info. He's very busy but does find time to respond to tip requests.

[Skip Fix]

At one time I think Carb Shop drilled and tapped secondary area hole for jets that were larger than the pressed in stainless inserts.
Also contrary to what has always been said richening the primary side some WILL richen the AFR at WOT .