[scott70]

If you wanted to slightly richen up the rpm range of 4600-5300 only would you do it with a secondary rod change or hanger change? Or is it even possible. Currently DA rods and G hanger. Just trying to learn here.Thanks

[25stevem]

Yes, with a secondary rod change.

Note that doing what I post here you can atleast richen up the transition, but not the full throttle air to fuel ratio.

A easy and easily reversible thing to do is to make a shim to go under the secondary rod hanger to set them up higher.
The safest way to go is to slice into strips and layer up masking tape which is .005” thick .
I would go with kicking up the hanger .015” at a time.

You could use a shim made from a Aluminum soda can which is .004” thick, or make some from the top sealing Aluminum of a Wine bottle which is about the same .004”.

Must well stocked auto parts stores stock brass shim stock in thicker sizes then these here that you could cut up shims from.

Just make darn sure that when using the aluminum or brass that it say’s in place .

Just note that you can’t shim up the rods as much as the end straight length of the tip of the rods , so note that length you have to work with first.
Leave .015” of length so the rods don’t pop out of the secondary jets at full throttle..

Note once again that this only richens up the transition, your tip diameter will still be the same .
There is another way to go about this but it requires the air horn to be off the carb and disassembled.

["QUICK-SILVER"]

Is the cam on the secondary air valve shaft lifting the rods to the power tip?

If so, I would try rods with a slightly smaller tip. Something like a CE.

Clay

Charts on these pages

http://hioutput.com/tech/qjetrod.html

https://quadrajetparts.com/-a-2.html

[Kenth]

Provided you have full throttle at those engine speeds, it is the secondary rods that need to be replaced.

["QUICK-SILVER"]

Originally Posted by Kenth

Provided you have full throttle at those engine speeds, it is the secondary rods that need to be replaced.

Add that, that needs checked with a helper holding the loud pedal on the floor and not just working the throttle under the hood.

Clay

[Kenth]

Where will you find a helper sitting under the hood looking at the air valves opening action at WOT from a standing start?
(We all know the air valves will open only with load on engine?)

[scott70]

On the engine dyno the A/F showed a little lean in that RPM range. Its a street car but I know what it can do at the track. I was going to make a couple of runs and then throw in a different hanger or rods and see if theres a difference. Sounds like the rods might be the things to play with 1st. Im probably not going to put in a A/F gauge,,,probably just go by track ET and mph and see if it likes it or not. Thanks for some of the links,,interesting reads. Now that its in the car with full exhaust it might not be lean anymore anyways. Just experimenting.

["QUICK-SILVER"]

Originally Posted by Kenth

Where will you find a helper sitting under the hood looking at the air valves opening action at WOT from a standing start?

Now now Kenth, I only did that one time and that was nearly fifty years ago.

Now tell everyone how I "use to" run down and catch wild cattle with my bare hands.

Originally Posted by Kenth

(We all know the air valves will open only with load on engine?)

I trained a finger to check air valve operation with the engine off. Just plain look to check secondary throttle blade opening with engine off. That's working the throttle lever by hand AND making sure the loud pedal opens the throttle all the way.

Clay

[scott70]

If someone has a good pair of CE secondary rods they would sell feel free to PM me. Just experimenting....probably wont amount to anything but thats OK. Thanks

[carbking]

With the talk of hangers and shims: ALWAYS replace the plastic secondary cam when rebuilding a Q-Jet. These items come in the better rebuilding kits; use them!

Due to the position of the cam in relationship to the rods and pivot; 0.005 wear on the cam means 0.010 less total lift on the rods. 0.020 wear means 0.040 less lift. I have seen cams with almost 0.050 wear, and Cliff has probably seen cams with more wear than that.

Jon.

[scott70]

The carb was rebuilt by Cliff top to bottom a few years ago.....Im sure he checked that out.

[400 Lemans]

https://quadrajetparts.com/quadrajet...128_44_49.html

Originally Posted by scott70

If someone has a good pair of CE secondary rods they would sell feel free to PM me. Just experimenting....probably wont amount to anything but thats OK. Thanks

Here is some.

[scott70]

Originally Posted by 400 Lemans

https://quadrajetparts.com/quadrajet...128_44_49.html Here is some.

I saw that...just seeing if someone here has some they want to get rid of. Thanks

[prostreet64]

Scott, if you haven't already found some, I think I have a set of the CE rods and will take a look at my spare parts in the morning and let you know.

[scott70]

Originally Posted by prostreet64

Scott, if you haven't already found some, I think I have a set of the CE rods and will take a look at my spare parts in the morning and let you know.

Sounds good,,thanks.

[Cliff R]

"Due to the position of the cam in relationship to the rods and pivot; 0.005 wear on the cam means 0.010 less total lift on the rods. 0.020 wear means 0.040 less lift. I have seen cams with almost 0.050 wear, and Cliff has probably seen cams with more wear than that."

Yes, and even worse they get loose on the shaft from shrinking some over the years which throws everything all out of whack. Amazes me to this day that folks "rebuild" their carburetors without installing a new cam/spring, are not able to effectively tune the secondaries, then wonder all over the Internet looking for someone to help them with issues in that area..........FWIW.......

[Half-Inch Stud]

Tuning value is found with the Street 0-30 Pull away evals (credit Cliff for this).

My efforts in tuning the Q-JET used the hard-pulls to assure the Pri Accel Pump played, and had knowingly set the Mech Secondary tab, had knowingly set the SecFlap tension, and picked the best Sec rods. Well,

the Pri Accel Pump Rod would always need the inner hole
the Sec Flap would need a fine tweak
the Sec hanger would remain a curiosity, but i would error on using the higher hole
Sometimes the HEI springs were the culprit if too weak; more off-idle power with firm ADV springs, then all in at ~2800 rpm

Now that Overdrive is in, the highway cruise transition to pulling power is amazing, but i have to think the VAC ADV is making up for the MECH ADV not all in. Then the MECH comes in with the pulls. 2500 rpm at 75 mph mean MECH is all in around 90 mph!