Does the picture on page 32 of the following q-jet write up match expert opinion on what should be happening with power valve height in primary venturis on an "RV cam" otherwise stock 455?

http://www.corvette-restoration.com/resources/technical_papers/Q-Jet_Carb_Tuning.pdf

My rods are no where near that deep. Movement marks from the jet on the rod are showing just barely gets near the taper fat part, much less sits within it.



Thus, the question of where the rods should sit.

TIA

Does the picture on page 32 of the following q-jet write up match expert opinion on what should be happening with power valve height in primary venturis on an "RV cam" otherwise stock 455?

http://www.corvette-restoration.com/resources/technical_papers/Q-Jet_Carb_Tuning.pdf

My rods are no where near that deep. Movement marks from the jet on the rod are showing just barely gets near the taper fat part, much less sits within it.




Backstory if you want to keep reading:

Many attempts (2 years) at getting my gas mileage up from 6 and 7 mpg and occasional but persistent overheating. Those two symptoms, plus nozzle drip and just barely a hint of surge/unevenness at idle. I bought a second carb (correct number but center section warped) to compare and learn from, and did a bunch of reading here and general web.

Several of our experts over time have recommended that I check the power valve movement, and it always moved, so we moved on. Now, I am thinking it is not seating far enough down. Both carbs I have are the pre-1975 style that have the APT adjust screw press fit covered. I pulled one press fit cover off the extra carb and voila, another q-jet adjustment.

I read that you can't mix rods from 1973 carb and 1975 carbs, as they used different lengths. I read this on a non GMC site, and not sure if our carbs were consistent over their production run. This got me thinking about rod height and seating more than simply stuck or not stuck. Next thought was that even if the non-oem rebuild kit gasket I have been using on these multiple rebuilds and cleanings are even a bit too thin, that is the same as adjusting the APT up (because the stop is on the bottom plate and the power piston comes down from the middle section, gasket thickness and density would affect this), which causes rich at all but heavy loads (when power piston would rise fully as expected).

My inexact method of verifying has been to mount carb bottom plate to center section with gasket, then observe jets in position while manually pushing the power valve all the way down.

And the full confession paragraph is that I hypothesized this before I learned of the press fit covered adjustment at the front of the bottom plate (next to pcv vacuum port). Many web sites said "early carbs" had no adjustment and I thought that was me. Apparently some 1960s carbs had no adjustment, early seventies had this factory sealed adjustment, and post 1975 had one geared up to the top of the carb for access without disassembly. So, on my good carb I literal persuaded the apt adjuster down with some hammer and screwdriver intricacies. ahem. put it all back together and first time ever absolutely no nozzle drip on passenger side, idle mixture screws behaving as expected and can kill motor. So it seems I am on right track and need to adjust with proper APT turn screw. Thus, the question of where the rods should sit.

Will I need to re-seal that adjuster hole? It does not seem that much vacuum could get by the adjuster screw.

TIA

Remember,
when there is no oxygen present in exhaust gasses, even at very high (over
3000 degrees) there will not be much damage to the valves or seats. BUT,
when oxygen is present, the valves and seats will be damaged, even at very
much lower temperatures. That is one big reason not to have leaking exhaust
manifold gaskets or open headers. Reversion of gasses will introduce oxygen
into the valve areas and oxidation will happen quickly. Like turning on the
oxygen valve on a cutting torch. Same amount of acetylene at the same flow
rate and pressure, but more oxygen results in cutting through 1/2" steel
plate like butter. Similar stuff happens inside your engine when you
introduce too much oxygen to the combustion process.
Just some of what I have learned the hard way. You don't have to. Just
listen and learn.
Jim Hupy
Salem, OR
78 GMC Royale 403