Quadrajet Secondary Testing 9/8/23

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@dbc105 Жыл бұрын

I've built and tuned a lot of Quadrajets over the years and I have one on each of the vehicles that are carberated. This is not advice, this is just what I would do if it were mine. I would tighten up the secondary spring just a little. Since you have it setup to watch it and drive, I would tighten a little too much and drive and then back off till you barely heard the roar. Typically the roar is just a little more air than the engine can take at the time. If you have it on a big block you may not be able to tell any difference as a good one runs so hard even when the secondaries are way to fast. But on a small block you can make a little difference. On my last El Camino tuning like that got the rear tires to break lose when you kicked it to pass. Before it just moaned. Good luck either way and way cool video.

@ryanbrunson777 Жыл бұрын

Thanks for the comment. I have played with air door tension, and will revisit it when I have the primaries working properly. So far it likes best to have 3/4 of a turn on the spring. I've determined that my primary mains aren't coming in soon enough, which is causing the lean condition at low speed. Basically it is running well off of the idle and transition fuel at low throttle angles, but the boosters aren't flowing fuel until above 2500rpm. My thoughts are that until I get the mains working right, there won't be a smooth transition to the secondaries at low speed. I recently discovered that my fuel level is below the booster nozzles in the primary main wells, which is likely delaying the main circuit. With the engine running and my removable air bleeds removed, I could see down into the main wells to see this. My plan is to fix my crossmember and trans mounts to get the engine more level, and then raise the float height or fuel pressure until the fuel level is high enough to start the main circuit fuel flow at a lower rpm. I can do more of these videos or videos to explain my Quadrajet modifications and experiments if there is any interest.

@dbc105 11 ай бұрын

@@ryanbrunson777 You're right, if the eprimaries aren't right the secondaries will never be right. A lot of kit guides will tell you to set your float level to .450, set it to .300 instead. That is a little higher and it will help with tip in. I can't remember but I want to say it was Pontiac on the RAM Air engines that set at .300. I've just set them all that way, you can always drop it if it proves to be a problem but al lot of times it will with the Off Idle response.

@frigglebiscuit7484 6 ай бұрын

this. they are NEVER supposed to moan.

@Joe-d1y 3 ай бұрын

The sound of those secondary's always makes me smile. Had a lot of hot rods, but always wanted to build a 500 HP Engine with good flowing Quiet Exhaust so I could hear the Secondary's sing better.

@Jbar362 7 ай бұрын

I really enjoyed your video. I hope you do another one. I have a marine qjet in my 1988 boat on a 405 engine. I have my wife at the controls while I try to adjust the mixtures to get the most response while under way. Your video helps me to see how it is supposed to look. On a boat it is wot. Thanks again! Awesome video.

@hendo337 5 ай бұрын

I am the 69th sub, great stuff. I have been wanting to build an LQ4 block I have with flat tops, porteds heads, a big cam, headers, single plane, electric cutouts with quiet mufflers and a Qjet just for the sound for a long time because I wanted to hear a 7000rpm engine with a Qjet in my 2004 GTO with a 6 speed. Even though I know it would probably make less power, I was right in guessing it would sound great and give a tiny bit of that old school Pontiac V8 muscle car character with a Qjet. I added this to my favorites. Thanks for the video.

@ryanbrunson777 5 ай бұрын

i installed the truck norris cam in june. it revs out to 7000 now and loves it.

@papaClutch415 2 күн бұрын

Looks like the accelerator pump lever isn't on the plunger

@ThatMacintoshguy9563 8 ай бұрын

Is there any way you can make a 3 hour loop of the quadrajet being romped on full throttle from 1st womp 2nd womp to 3rd womp and 4th womp

@robertlucas1435 6 ай бұрын

i need this so bad

@frankcarter8399 11 ай бұрын

Cool video. I read your other comments. Are you talking about the fuel level not being high enough for the two side bowl areas that supply the secondaries "tip in" supply? Thats definitely a problem if so. I'd be interested in seeing a little more testing once you play with that more. I also agree on the secondary spring being a little soft but if it's leaner than it likes you should focus on that first. Remember, the more consistent you can make it the easier it is to tune. Cheers to you!

@ryanbrunson777 11 ай бұрын

Hi Frank, Thank you. This is a Quadrajet, so it has one central float bowl that feeds everything. In my other comment I'm referring to the primary side of the carb. Since this video, I took the link out for the secondary throttle plates, effectively turning it into a two barrel, to see if the bog was related to the primaries or secondaries. I have a lean spot above half throttle at low rpm between the transition circuit and primary main circuit. Above half throttle the transition circuit loses signal as the most narrow path for the airflow becomes the venturi and booster area. This is where the primary main circuit is supposed to start flowing fuel and take over. I have been trying different mods to bring down the booster tip in point so that there is a seamless transition between the fuel circuits. So far I have raised the fuel level, am running a dual plane intake with a divided spacer, have slimmed the throttle shaft and knife edged the throttle plates, worked on the booster ring aerodynamics, and have played with different jetting and air bleed sizes. It has all improved the problem, but it still exists. I have more ideas that I'm working on. I think the problems have to do with that I'm trying to make an 800cfm Qjet work on a smaller engine. I have a 750 Qjet, but want to give this my best try before I go another route.

@frankcarter8399 10 ай бұрын

@@ryanbrunson777that's the 800cfm? A 6L should take advantage of that fine id think. That's pretty big. So you've locked out the secondaries and you're still having a lean spot between the transition port falling off and the main jets kicking in?.. perhaps it's a lack of vacuum signal at the ventures like you were saying. Tho I wouldn't know how to help you there. I was talking about the two chambers between the primary and secondary bores that fill with fuel allowing the smaller pickup tubes to pull fuel into the secondaries just as they start getting a vacuum signal before and just as the vacuum actuated doors begin to open. The holes that fill those chambers are very small and can clog. Could help if that flat spot lines up with the timing the linkage would be opening the secondaries.

@ryanbrunson777 10 ай бұрын

@@frankcarter8399 Now I understand what you meant. those wells add fuel to the secondaries for secondary transition and keeping a level fuel curve. As you probably understand, they aren't in effect if the secondaries are locked out. My problems do seem to be between the transition port and main jets. I'm going to try my 750 out and see if it makes a difference. The primary side is about 150cfm rather than 200cfm, which is a big difference. I like to be able to stomp the throttle without downshifting at times, so I might have just been expecting too much from a big carb on a small block in a heavy vehicle with a manual transmission.

@oldguyhobbies4627 10 ай бұрын

Very helpful video to see what is going on when the Qjet opens up, thank you. Engine sounds good too. How did you film it and especially how did you film it without a ton of wind noise? I'm trying to maximize the Qjet Bwahh sound and trying to figure out what causes it. What model engine is it on and does it have the factory intake or aftermarket? Thank you!

@ryanbrunson777 10 ай бұрын

I made a clamp for my phone that attached it to a hood brace. It was a couple folded pieces of sheet metal and masking tape. For wind noise, I have been tuning my engine without a fan, so that I don't have to work around it with fingers and hoodie strings. As long as you don't sit still too long with the engine running, the coolant stays happy. For the bwahh sound, my best guess on why it happens is that something resonates, possibly the air door since it has some freedom to flutter. The sound, wherever it comes from is then amplified by the megaphone shape of the secondaries. I don't notice the sound much from mine, but it could be that the exhaust covers it up.

@jimvanhook 8 ай бұрын

How are you adjusting the FAR so precisely? Awesome to see in action.

@ryanbrunson777 8 ай бұрын

I appreciate that you consider it precise. There are many tuning points on a qjet. They all impact some areas more than others, but they all have impact on each other, so it can be tricky to get a carb to run right in all circumstances. I have a lot more tuning to do before I'll be happy with it.