Q-Jet secondary adjustment

Discussion in 'The Venerable Q-Jet' started by Mark Demko, Jun 25, 2021.

  1. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

  2. hugger

    hugger Well-Known Member

    Ugly ain't it! Haha,..he'll it even had really good cold start manners,...3 pumps up and running no feathering or anything,...could sit for months on end and just go to work

    Ran a B hanger and AU rods iirc
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    HotCrazyMatrix.JPG
     
    FLGS400, Mark Demko and techg8 like this.
  4. hugger

    hugger Well-Known Member

    Oh trust me I spend my time in the orange quadrant,...ah hell,....and some in the red not gonna lie
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    :D:DBe careful, one almost did in our friend Jason.:eek:
     
  6. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I wondered if his new flame was the source of his troubles!
     
  7. Mark Demko

    Mark Demko Well-Known Member

    LOL I agree, If its a warm weather driver, and you cant feather the throttle till its warm and behaves good your not a car guy:D
     
    1972Mach1 likes this.
  8. Mark Demko

    Mark Demko Well-Known Member

    LMAO HELL YEAH:p:p:p:p
     
  9. Mark Demko

    Mark Demko Well-Known Member

    I appreciate EVERYBODYS input;)
    Cliff knows his Q-Jets, and how they function, THAT helps me TREMENDOUSLY!!
    I dont operate a choke, its there, but its wired open.
    Being Hugger and Im sure others, have eliminated the pull off, and adjusted the spring tension to control secondary opening, Im taking that as a valid "trick"
    Im bolting my DR's back on for more traction on the street, spinning tires dont tell me anything:p maybe with my DR's, I can quantify improvements if any, I cant do it with street tires, and I dont wanna wait till the track, yeah the traction will be there at the track, but I want to know my bog is gone, otherwise I'll have wasted my two or three passes.
     
  10. Cliff R

    Cliff R Well-Known Member

    "I'm not insinuating that this is the case with Mark, but I could only imagine the crap Cliff deals with.. i would not touch that homemade secondary spring crap either."

    Seriously guys I could care less what folks do with these things. I make a really nice living because people do stupid chit, poorly informed, get bad advice, don't know what they are doing, believe inaccurate information they read on these Forums, and watch really cool YouTube videos from folks who really need to keep their day jobs and stay away from carburetors in the first place.

    I've been at this deal for well over 4 decades and still haven't seen a rule-book anyplace about what compression to run, what cam to use, or how to attack your carburetor with a chainsaw and hack it all up leaving off many of the needed parts in your efforts to make things work better.

    IF what you've done works and puts a smile on your face I'm really happy for you.

    These Forums are here to educate folks and help them with issues they are having. I think most of them are smart enough to know what piss-poor advice is and to avoid going down that path.

    I'll leave you with a cool story about removing the choke pull-off and link up to the secondaries, because stories reflect real life experiences, here goes.


    In recent years rules are now allowing Quadrajets to be used in many circle track racing Classes. So all over the country folks are going to them. I typically avoid that deal but got involved with one from a customer in the deep South that wanted to up the game with his car. He had a local "guru" do his carb and of course he removed the pull-off and link so the driver could "feel" it kick-in anytime he got back on the throttle hard. Common practice but my customer didn't like the big "lunge" and at times it would actually bog or "lay down" so he found himself winding the spring tighter and tighter until one day it broke during a big race and they ended up in last place.

    So he goes on the Internet and ends up calling me. We have the SAME discussion as I've had countless times on that topic and I agree to take a look at his carb and set it up for what he's doing. I'd also add that this customer is a pretty sharp guy, he has money to spend on these things, his engines are top shelf considering the Class Rules and budget, so all he really needs is a good working carburetor to seal the deal.

    I get the carb in here, it's nothing more than a mid-70's Chevy divorced style carb with a Pep Boys rebuild kit in it. No HP pump, no high flow N/S assembly, broken secondary spring no venting modifications done anyplace (big deal with racing carbs but that's a story for another day). About all I see for "modifications" are two HUGE holes drilled in the primary throttle plates for bypass air....it gets new ones that aren't drilled.

    Anyhow, I go thru the carb, ditch the power piston and set it up to run straight off the jets, idle system mods, HP accl pump, high flow N/S assembly, small float, vent mods to keep ALL the fuel in the carb when going around the track and on/off the throttle, new secondary cam, spring and one of my adjustable choke pull-offs for a smooth/quick/clean release for the airflaps.

    I don't here a word from him for at least a year and actually forgot about even doing the carb. Then out of nowhere I get a call from him. He is now the local track Champion in his Class and went on to win just about every single race he entered. He tells NO ONE who did the carb and keeps it hidden so wondering eyes don't see it walking by his pit sight. After a quick thanks for the work for helping him out we end the discussion and I get no more business from him or any referrals, etc. (That's the way it ALWAYS goes with that deal so no surprise here).

    So jump ahead to a few months ago. I start getting phone calls and orders for my adjustable or "timed" choke pull-offs from several circle track racers. A few also bought complete custom rebuild kits with high performance and tuning parts in them. I guess someone let the word out about the carb I did for the customer above because the orders are coming from the same area.

    So a good ended to the story, but typically "race" stuff does NOT pay big benefits. It's time consuming and most of time few if any referrals come from it..........Cliff
     
    Last edited: Jun 29, 2021
  11. Cliff R

    Cliff R Well-Known Member

    A quick comment on chokes.

    I removed the choke from my Q-jet back in the 1980's and didn't really miss it that much. I was racing the car couple of times a week and also set it up to run straight off the jets so no power piston or primary metering rods used either. The carb was flawless for what I was doing and "fat" enough there wasn't a lot of endless pumping the throttle for cold starts or "feathering" the throttle till it warmed up etc.

    In that configuration I won the big Pontiac race at Norwalk 5 times with two trips to the King of the Hill race (last man standing) twice, and logged dozens of wins at local tracks and fast street car events, etc (and YES I'm using a "timed" choke pull-off and link up to the secondaries). No real issues except for the rare occasion I had to move the car off the lift in the middle of Winter and it was a royal PITA to start and keep running if below 30 degrees or so. I just dealt with it, no big deal.

    About 10 years ago I decided to put the car back on the street more and went from racing it at every possible opportunity to a couple of times a year. So I removed the carburetor, put jets and rods back in it, electric choke, quieter mufflers, full length tail pipes, back to the stock intake from the RPM, stock Shaker and air cleaner assembly from custom air cleaner assembly for the "modified" Shaker assembly, etc.

    I figured it would slow the car down some but those modifications made for INSTANT starts in any weather, fast idle for warm-up, and improved characteristics for street driving.

    I was loving it, no more pumping the chit out of it in cold weather, quiet, excellent street manners, etc.

    So I wonder over to our local track for a Friday night test and tune. I got there early, didn't even shut the engine off, dropped the tire pressure to 18psi (DOT's), and make a pass.............7.18 @ 97mph!

    It actually ran a tad quicker in that configuration that it did with all the "high performance" modifications on it! I did loose some MPH and a little top end charge in the 1/4 mile when I ran at a different track a few months later, but not all that much considering how many "high performance" parts I'd removed. I still managed low 11's at 119mph instead of 120-121 which it typically ran in the DA I was seeing that day.

    So my choke is back on and here to stay.......FWIW....

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  12. Dano

    Dano Platinum Level Contributor

    Thanks for sharing your knowledge with us!
     
  13. Cliff R

    Cliff R Well-Known Member

    You are most welcome.

    I try to stop in and help out when I can. My time is somewhat limited, watching my grandson today so have some computer time until his dad picks him up, then back to the grind.

    I try to tell stories, as they reflect real life experiences and testing parts, etc. I'll also emphasize here that I LOVE testing parts. Folks selling aftermarket "high performance" parts are also marketing genius's and to get folks to pull the trigger on some of this stuff they tell us it leaps taller buildings, walks on more water, tucks you in at night and cooks breakfast for you the next morning. I don't buy into all that and love nothing more than bolting something on at the dyno or even better at the track to see what's really up. I have EXTENSIVE experience testing carbs, intakes, spacers, camshafts, bug zapping ignitions systems, headers, mufflers, head pipes (X and H) and just about everything else you may have looked at using on one of these engines. If you really want details and the results I've seen don't hesitate to ask.

    Anyhow, if anyone is paying attention I REMOVED an Edelbrock Performer RPM intake and went back to my factory intake. The factory intake is 1" shorter with slightly smaller runners but generous for plenum area and very well designed.

    My engine will also make over 550hp/600tq, yet at the track in the 1/8th mile it went QUICKER in ET with the factory intake and other minor modifications to return it to "street duty".....Why?

    I think one reason it ran quicker with the stock parts was partly due to the "cobbling" involved trying to use the factory Shaker assembly with a 1" taller intake. This moves the carb UP and requires a 1" shorter Shaker top and 1" shorter air filter and at the same time moves the lid 1" closer to the carburetor. When I first tried that deal it didn't run well at all so I had to completely remove the air filter and lid and make a custom filter for the opening in the Shaker. I thought at that point I was good to go.

    The factory air filter set-up and lid are very well made parts and the lid has a nice rise in it and radius to guide the incoming air into the carburetor. I really think that is enough of an advantage over running with no filter and lid that the engine made more power and car was a little quicker.

    I also added quieter mufflers and full length 2.5" mandrel bent tail pipes at the same time so the slight restriction in the exhaust may have also helped with low and mid-range power. Even if it didn't the car is a LOT nicer to drive on the street, no "drone", or buzzing at any RPM and you don't have to scream at the passenger to have a normal conversation!

    Anyhow, babysitting time is over, back to the shop to fill a stack of parts orders and return a few tech calls so I can solve a few more of the Worlds problems today!........Cliff
     
  14. LEgendVI

    LEgendVI Well-Known Member

    The OP is exactly what I was looking for. Set my choke, idle, air/fuel, getting 19" of vacuum BUT when I go WOT I still get some hesitation. Not as bad when I first started troubleshooting but still there. Secondary's are as loose as it is hot in west Texas. Heat of the day... taking a break for my own good.

    Probably have to adjust the choke again once I tighten them up no?

    I've got a few minor open vacuum leaks I've not figured out yet but all in due time.
     

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