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Still trying to straighten out this Qjet, took it down again to put a lighter power valve spring in.
Then I spot these secondary metering rods noting the cuts are not equal nor have I ever seen rods cut like this.
So I source and match another pair and go to install them.
I find the hanger is holding the rods up 3/16" as I go to put the hanger screw in.
So I find a letter matching hanger and install it and the rods are down where they should be.
We will see if this cures it, but my god has this car been messed with.
This is the video of the hanger change.
As 67OAI points out the slots are intentional, also the 3/16" change when secondary hanger screw is installed is normal. Since these items are on the secondary side they won't affect normal driving economy. Contact Cliff Ruggles for proper PRIMARY jet/rod combination. Did you notice fuel dripping from primary nozzle at idle? Fuel pressure should be 5-6psi. Distributor re-curve may help increase power. You never stated vehicle/engine combo or application. Check throttle plate position with carb inverted.
What caught me eye is the slots were not equal.
The explanation makes perfect sense.
However, with respect to the hanger position, these wells would easily fill due to the fact that the hanger with air valves closed is lifting the rods up out of the seats 3/16".
That video clip shows the original hanger and another one that would allow the rods to seat properly.
Those 2 things are what struck me as odd.
Not only that but the link that Fun put up and the "hop up" comment had me calling Summit to see what the purpose was.
I went through three techs in support getting handed up to one that said he needed to do some research and would call me back, that was Friday.
No word back yet from them.
I need a shop with a flow bench to set this thing up.
That or a new Weber/Edlebrock...
Rick, regarding your input in post #8 above, the secondary rods do not have to "seat" in the secondary jets. Rochester tuned the QJ carburetor for each specific model usage and used one of many different height secondary rod hangers when doing so. In the Dog Roe carburetor book which I reference, 20 different height secondary hangers were manufactured, each one .005" different in height from the previous for a total of .095" from "richest" to "leanest". It is not unusual for someone to have bent one of these hangers to get those rods to lift out of the jets a little or a lot more. As "Dragline" mentioned, the secondary circuit will not affect normal driving on the primary circuit, that is where you need to concentrate efforts. It may be worth your time to give Cliff Ruggles or the guys at Everyday Performance a call! Good luck.
With the hanger secured with the screw, the rods were up 3/16" of an inch out of the wells.
Meanwhile in t his long bullship gauntlet of getting this engine to run right a buddy had a new Edelbrodk AVS-2 in a box.
Got nothing to lose except time at this point.
I bolted it on with a spread bore square bore adapter last night and replaced the exhaust gasket also plaguing this engine.
Took it for a ride and the first thing I noticed was it started without touching the gas.
The second thing I noticed was my power brakes were nearly twice as powerful
The third thing I noticed was omg this thing screws now.
So not sure what is next with this qjet, but for sure something is up.
Just glad to have things running like they should be.
I will certainly explore getting the qjet properly overhauled and bench flow tested before I put it on the engine.
Any recommendations from those with personal experiences with problem carbs are welcome.
Thanks again
r
When i broke into my qJet for a rebuild, I quickly realized someone had played inside the carburetor prior to it coming to me. To increase the likelihood of a good outcome, I called Cliff Ruggles who told me to ship it out to him. It was the best decision I could have made since I found Ruggles personable, capable, and reasonable. Just my 2-cents worth.
The weight of the rods tilts the hanger forward when not secured. Installing the screw properly locates the hanger with no movement.
Thanks for reply. I previously tried to play that video multiple times over the last 2 weeks and it played for appx .5 second and reset, time after time. Tonight the vid actually played through for the first time for whatever reason and now I get the reference.
Those secondary rods look like the result of an optimist and a dremel cutting wheel in search of richer secondaries.
Back in the pre-digital age there were all kinds of theories about making qjets better. What we see 30-50 years later is more or less the archeological remains. The furthest I ever went was cutting Pontiac style notches in the secondary upper blades of a couple of my qjets. Just trying to say, I’m guilty of testing some questionable modifications too.
My moves on seeing this would be to put the qjet as close to factory as possible and get rid of non-factory modifications.
The good news is replacing rods is a 2 minute affair.
Well the problem seems to be vacuum based.
When I drop on a new carb and the car performs it only leaves one thing.
This problem has been an off idle problem that with lighter primary plunger springs have helped considerably.
The secondary side is the air valve spring adjustment.
Another tech told me to set it so it just closes which also helped.
But being torn of what the problem was, this new carb seemed to be a good route because it was available instead of me just buying one to test with.
When I posted this I was on back roads.
Since then the highway performance is incredible.
So I just got off the phone with Cliff, omg he had me in tears, what a funny guy.
Smart too, knew what the problem was in a second and its the cam overlap.
Looks like a winter project is coming and he's gonna help me get a cam in there that will work much better.
So I just got off the phone with Cliff, omg he had me in tears, what a funny guy.
Smart too, knew what the problem was in a second and its the cam overlap..
Ok, can you explain that to the laymen of the group?
Ok, can you explain that to the laymen of the group?
Well he is not a Comp Cam fan that is for sure.
The lobe separation is 110 degrees which is too close and effecting base vacuum.
The other thing is compared to the stock cam, the duration is less with the lift being more which reduces the amount of airflow into the cylinder in terms of how long the valves are actually open or begin opening..
He mentioned they sound car show badass, but from a power stand point not a good choice.
Also said he could achieve the same thing by retarding the timing and closing up the idle jets which cracked me up.
So he is going to help me select a cam and get this Qjet squared away over the winter months.
From the start I knew this problem was engine vacuum related, this Qjet worked perfectly on the stock 350 that was in the car.
I do have the original 401348 GM cam that was in the 400 when I got it mostly disassembled.
I didn't pick out the cam on this build, my machine shop did based on other Olds engines they've built.
My brain is driven by logic and this problem totally escapes me.
This Qjet ran flawlessly on the Rocket 350 that was originally in the car.
Since March when the 400 went in it has run like absolute **** which I along with other people smarter than me concluded was the cam's low vacuum causing the problems.
So after a week of running this with the AVS 2, in all regards the changes are profound.
From cold start, to acceleration, to fuel consumption its leaps ahead of the Qjet.
Drop it on, set the idle mixtures at 1.25 turns and its got this 400 singing a totally different song.
At this point I see no reason to change the cam and for the sake of keeping the engine original may have Cliff set this Qjet up for me even though it might not improve which he assured me it would although not as much as a cam change.
However that said, the car has 3.08 gearing which is great on the highway although never gonna be a street racer or 1/4 mile winner, thats not my thing anyway.
Its gonna get a locker next month and I'm leaving the ratio alone.
Its just that I have no logical reason for one works so well and the Qjet is so bad after being on the 350 running perfectly.
The power valve spring adjustments helped, but even then the idle speed and tone is night and day between the two of them.
September 15th, 2021, 09:37 AM
