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Ok, the float was way off, bent and crimped enough it would not fit the housing and sat too high. So I set the float to 1/4", a starting point Cliff recommends for high performance builds. I checked it flipped upside down and with tension on the float right side up. It is easy to over leverage the float in the right side up positiion. The float Cliff provides is smaller than the one that was in the carb, a good thing. I kept the second lightest power piston spring as a starting point. Cliff's accelerator pump is shorter, has the inner cup spring and is ethanol resistant. The accelerator rod with the little clip makes removing the top much easier with the carb on the motor. New fasteners and lock washers included in the kit is a nice touch. The passages are blocked in the hot air housing allowing the conversion to electric choke. It also has his fast rate pull off, I just put one on the other Qjet Everyday Performance custom tuned for me. I just need to check the secondary air door opening and pick the secondary hanger and rods from my assortment as a starting point and this carb is done. This carb will get tuned with the recommended wide band from Cutlassefi on the new motor.
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Air door set to 1.300. Edelbrock claimed 850 cfm with a 1.27 opening on their RPM Qjet. Cliff suggested up 1.300, he has 1.310" on his 650 hp Pontiac. I put a H hanger and CK rods to start. I have 71, extra 73 jets which are questionable and 74 primary jets. I have B, H, I, J, K, L, M and P hangers. I have CC, CE, DA, CK, CV and AY Secondary rods. It should be ready for the new motor.
Cliff's wording on the secondary air flap adjustment is confusing and contradicting in his book. The smaller the measurement, the more open it is FYI. He claims Edelbrock's 1.270", 850 cfm measurement should be the max opening yet he has a 1.240" to 1.300" measurement for his highest performance 3rd recipe. I think the 1.270" is where I am going to adjust mine too. Our Olds V8 seem to love larger CFM.
Your qjet work looks great. Hope you’re enjoying it. I’m no expert, but a couple of suggestions may help.
Sometimes the power piston arms are bent up or down. This will make one side rich or lean. Make sure the primary rod holes are exactly the same height for consistent primary metering
Its not part of the design, but consider adding an O ring to each idle screw in front of the springs (carb side, not screwdriver side) to seal up a 40-50 year old idle screw passages. Other than obvious vacuum leaks like the throttle shafts or bad gaskets, this helped my cars idle smoother. I hear some motorcycle carbs are set up with O rings. Worked for me anyway.
Biggest & best tip for last. Get yourself an 02 sensor from Innovative Motorsports or similar. It’ll really help you dial in your carb at different loads and RPMs’. I’m running dual 02 sensors in my exhaust pipes and it really furthered my knowledge of Qjet tuning and very very quickly. Other than that I was pretty much guessing and driving and stabbing in the dark at new combinations of jets, rods, springs, power piston heights, and so on. Once you can see AFR or Lambda, your level of precision and tuning really goes up.
Single sensor models will do the job at about hundred bucks less than the dual sensor models.
Great tip on the teflon instead of bronze bushings. I’ve never heard of that, but it sounds just great. Must try that sometime.
If you dig around under my user name you’ll find some other qjet related posts which reflect some of my learning along the way.
I like the o ring against the mixture screws idea. I went with the bushings in the throttle shafts due to not finding the appropriate teflon. I am getting a AEM wideband from Cutlassefi along with the rest of the parts to build my 350. I may actually use my current Qjet as this one may be a bit rich at idle but I will at least try it out and see how close I can get it. At least I have a back up.
I went with the traditional bronze bushings too. The teflon bushing-equivalents sound great, assuming they don’t melt with intake heat.
Since my machining skills are non-existent, I buy carbs from SMI (Sean Murphy Induction) who do most of the mods you’re working on. They get more or less $500 for an 800 cfm center inlet qjet. That’s worth it, to me. But SMI carbs usually arrive jetted too rich for my mild big cars. So I tweak.
I’m in full favor of bushing your own primaries and rebuilding your own carbs, but I’ve goofed up too many baseplates to fool myself about my skills anymore.
You’ll like the O2 sensor a lot. It’s a kick seeing realtime AFR or Lambda at idle, cruise at 35 mph, 55 mph, and slightly into the secondaries at 70 mph. For the scaling, I started with AFR and wound up at Lambda when using the O2 sensor. AFR is easier to understand, but these gauges really measure Lambda and scale over to AFR. I switched scales about a year ago and like the lambda precision better — basically you aim at 1.00 lambda for most driving situations and correct for errors on the high or low side with idle screws, jets, rods, power piston springs and so on.
For reference, my big blocks run lamba 94-1.00 at idle, at cruise they vary between .96 and 1.05, when I nail it and the secondaries go wide it gets down to .85 or so. Close enough for me for now, but at least improvements from here can be guided by something a little more accurate than amateur guessing. I’m admittedly a rank amateur.
Anyway sounds like you’re well on the right track. Tune, drive & enjoy.
Thanks. I almost did this the last time, I waffled and Everyday Performance did the last one, the tune was much better than the super lean 79 403 emissions calibration. There were issues with my choke on my current carb that he did. It would bind and stick on. Cliff mentioned to me, once it separates, it has to be replaced. I actually had to add a washer to stop the binding. I eventually stole the choke pieces of a dual jet, never an issue again. Probably the nicest feature of my current and now this Qjet is the adjustable APT. Add a thread top plug and notching the APT takes minutes. I loved going from good fuel economy to tire burning power in 5 minutes. I actually gained at the track doing 1/2 turns on the APT, every run gained .1.
I think the choke issue washed out #7 and #8 on my $120 great running 350. I am pretty sure the cam went flat first which eventually took out the bearings. I got over 5 years use, two head and cam swaps and multiple 1/8 mile runs. Hell, I went through 3 or 4 transmissions, that still factory 76 short block owes me nothing. It is at the machine shop currently being held hostage. The cylinders had no ridge and I am betting they will clean up at 4.065". My other 350 which I am gathering parts, was a reserve car, which meant a lot of abuse. It needs an overbore for sure, I am ordering 4.125" custom pistons for it to work with my 3.5" stroke 330 crank. Even if the current 351 ends up too mild at only 350 hp for this carb, the 374 won't be. The only way my Qjets will go away is sequential EFI. Never say never, especially if emissions laws ramp up on old cars in Canada.
This thread was a great read. I've been speaking with Cliff at length and he helped convince me to ditch the 750CFM 4150 on a spread bore adapter that a former owner had installed on my 67 400 in my 68 422. I just received my 800CFM Q-Jet core off of a 403 yesterday. Waiting for some free time to start ripping it apart. Inspecting it, and ordering parts from Cliff. My eventual plan is to go Holley MPFI with either the HP or Terminator X ECU on my other engine for this car. But that costs allot more, and until I can gather enough funds together for everything needed for that install, I need to get and keep this engine running as good and safe as possible. So, I'm hoping that I can learn a bunch, build this Q-Jet cheaply, and am looking at a couple different options for a logging wideband 02. Fast, Zeitronix, Innovate, and AEM all have some comprehensive offerings.
I too plan on sequential EFI from Mark in the future. I may have went a bit too radical for the 350's 350 hp 218/218 duration roller cam. I decided on less power to hopefully keep this 2004R alive. I am tuning this one with a AEM wideband coming from Cutlassefi. I am currently having flooding issues with my current Qjet built by Everyday Performance a few years back. The tune on it is great for a mild cam. If this one I built is too rich at idle, the current Everyday Performance tune Qjet will get a kit put in it and tuned to the new motor with a wideband.
Last edited by olds 307 and 403; May 18th, 2021 at 11:26 AM.
Was just relooking at the pictures. Don’t forget to seal up the passage between the now-electric, formerly heat-controlled choke coil and the main body of the carb. Most kits supply a white plastic tube with a donut in the middle. I just melt the plastic to seal it up. Or use JB weld to seal it up permanently. It’s a small passage that may contribute to vacuum leaks toward the front passenger side of the carb.
When adapting these later carbs to 60’s models, it can be a good tweak to drill a second throttle rod (or cable connection) hole just below & forward of the factory hole on the vertical throttle blade connection. It makes the throttle response much more direct. If the factory hole feels slushy, drill a 5/16”s hole just below and in front of it. Just be sure you’re offset up enough vertically to make the throttle blades open easily.
You might also look up how Pontiac notched their secondary airhorn blades to drizzle a bit of gas into the intake before the air blades opened. Fun tweak. Not sure if it helps.
Also once a year or thereabouts, I snug up/tighten the airhorn screws working from the center outwards. Vacuum metering as designed depends on minimized leaks which can creep in after repeated heating/cooling cycles - a.k.a. using the car.
Here & there I spray a bit of lubricant on the stuff that is supposed to move/rotate freely.
With carbs, cleanliness really is next to godliness. Chase holes, polish the power piston bore, clean everything to minimize weird behavior.
Yeah, the passage in the choke housing was sealed with a orange RTV by the previous owner. I notched the secondary air doors like Cliff showed in his book, to help secondary transition. If that is what you are referring to. I also retighten the screws occasionally, they back off. I cleaned and then cleaned some more inside the carb, probably still needs more cleaning😁
Last edited by olds 307 and 403; May 18th, 2021 at 07:34 PM.
So my poor temporary Olds 350 didn't stand a chance in surviving. Not only did I have an issue with the Mallory distributor, now replaced with a HEI, I had an issue with the supply to the distributor. The connection came apart, so I upgraded to a bigger gauge wire and soldered the connection, 12 volts at the distributor. I thought the ignition was the flooding issue over half throttle, nope. Something is up with this Everyday Performance tuned and rebuilt Qjet,17058250, a 78 Oldsmobile 403 carb. It has been used for at least 5 years and has worked well other than choke linkage issues which required replacement to fix. I talked to Cliff Ruggles and ordered a SR kit which comes with a float, the secondary air door cam and spring. I also ordered his better 44 primary rods, he knew the carb came with 73 jets. He is sending a power piston spring as well. I know Ken used different primary rods than the factory 44K rods since I put 72 jets in it, that makes sense. I made the APT slotted and adjustable with a removable plug in the air horn before I sent it to him. I idled so much better when it came back. Cliff Ruggles had nothing good to say about carbs he saw built by Everyday Performance, which I was surprised by. He said expect a ball point on spring under the power piston and the rod hangers severely bent and the float way off😳. Ken told me he rebushed the secondary throttle shafts, I will do the primary throttle shafts since Cliff's kit came with enough to do two carbs. I am really curious to open this carb now, maybe Cliff got a bad one?
Just bought a used Edelbrock 1904. Previous owner could not get it to idle or run clean.
Once apart I found nothing odd. When putting back together I found it had the old short version primary rods. They up out of jets and floating around. Had 1 set of the new style rods and car runs very well after 1 jet change.
I basically have only dealt with the 76 and later carbs, so that is all I have around. I knew about the difference in primary rods. That is basically like running a W30 or W31 carb without compensating jet size!
I basically have only dealt with the 76 and later carbs, so that is all I have around. I knew about the difference in primary rods. That is basically like running a W30 or W31 carb without compensating jet size!
On the race car I dont run the primary rods. The difference with or without rods is roughly equal to 4 jet sizes. I have not adjusted the rod height yet. Need to remove plug in top and install threaded plug so I can make adjustments quickly.
On the race car I dont run the primary rods. The difference with or without rods is roughly equal to 4 jet sizes. I have not adjusted the rod height yet. Need to remove plug in top and install threaded plug so I can make adjustments quickly.
I works great, I would never build another Qjet without an adjustable APT. Wow 4 jet sizes, it would have been very rich.
I works great, I would never build another Qjet without an adjustable APT. Wow 4 jet sizes, it would have been very rich.
It made sense because that was what previous owner stated what the problem was. It had 73 jets and I went down to 68 with proper rods and idles well and accelerates ok for a 350 2.78 rearend
I recieved the SR kit with Cliff's 44 primary rods and his choice for a power piston spring, the orange one for my 78 403 800 cfm carb done by Everyday Performance. I will be doing the primary throttle bushings and air door cam. It will be interesting to see if any of what Cliff said was true or just one bad example of an Everyday Performance Qjet. I will be doing this next weekend. I also didn't like my attempt on the custom bent 3/8" Ni Copper line I used. The Ni Copper brake lines were amazing to work with, the larger line kinks much easier and I need a couple of tight bends. I will pick up 2 this week and really take my time to get nice bends.
I recieved the SR kit with Cliff's 44 primary rods and his choice for a power piston spring, the orange one for my 78 403 800 cfm carb done by Everyday Performance. I will be doing the primary throttle bushings and air door cam. It will be interesting to see if any of what Cliff said was true or just one bad example of an Everyday Performance Qjet. I will be doing this next weekend. I also didn't like my attempt on the custom bent 3/8" Ni Copper line I used. The Ni Copper brake lines were amazing to work with, the larger line kinks much easier and I need a couple of tight bends. I will pick up 2 this week and really take my time to get nice bends.
Try putting sand in tube before bending. It acts like a solid rod and helps to not kink.
Since we're on the subject, here's a mechanical tweak I like on my Qjets. I'm using late 70's 800 CFM center inlet units on my 455's since I like the bigger carb and figure that by that era they'd worked out most of the design kinks.
Since I'm swaped a late 70's era qjets onto 1966 big cars, there's a difference in throttle control. In 1966 GM was using rods to connect your foot to the carb. Per Joe P. they switched to throttle cables when some motor mounts broke in some cars and GM got sued because cars were pinning the throttle rods and hurting/killing people. So GM switched to throttle cables later in the 60's or maybe early 70's for safety. In my 66's there is a fairly rare but good functioning combination switch that controls kick down and the switch pitch stall angle. So I elected to keep that since I like it and it works.
When you adapt a late 70's qjet to work with 60's throttle rods, you need to make holes for a rod connection where there are ordinarily pins to connect a throttle cable. With the qjet off the car and the throttle plate on the bench, this is quick with with a dremel and little grinding disc. Bzzz and out pops the pin, leaving a nice 5/16" hole to connect a rod to. This works well, but leaves the gas pedal feeling lazy, sloppy, or loose, whatever you want to call it. In the extreme, you don't have enough movement to completely open the qjet to its intended 800 cfm or sometimes it won't kick down the transmission when you nail it.
Here's my solution, another throttle rod hole: Improve your throttle response by carefully drilling a 2nd hole in your late 70's qjet just in front of and below the original hole.
There are a bunch of things to be careful about:
First drilling & grinding on a throttle plate without protecting the mechanism can lead to vacuum leaks. I put the bronze piece in the vise with no pressure at all on the aluminum piece before working on it. And uh, don't do this anywhere near flammable gas or other stuff that can burn your house donw.
Next, you'll have to dremel off a bunch of now-superfluous metal from the vertical piece to allow free forward/aft movement of the throtttle rod. As I recall you need to remove some chunks off the rear of the vertical member and maybe 1/4-1/3 of the horizontal lower part which connects it to the throttle plate itself. I was originally worried about the mechanical integrity of removing metal, but mine have been just fine. Not a whole lot of pressure once things are adjusted right, just return spring pressure really.
Next, you have to be careful to locate the new hole above the pivoting pirmary throttle rod or the throttle rod won't pull the blades open. It'll just bend and trash the unit. Put another way, you want the hole offset up and forward of the center of the rotating primary rod circle.
Finally you want to polish the hole and use some nylon or rubber gaskets/spacers so that the surface the throttle rod pivots in is absolutely smooth. The smoother it is, the less binding there will be and the smoother the gas pedal will feel.
There may be opposing opinions, but this has worked for me for a few years. I just hadn't gotten around to posting a picture which told the tale. If any of you do have safety warnings for me or others, please pass them along.
While I was tweaking my qjet this afternoon, it struck me that you guys might like an idea I hit on long ago: a qjet tuning box. If you're into these ancient devices this deep, it really helps to have your parts organized and sorted. This is all late qjet stuff, I didn't keep my early stuff since I didn't want to confuse similar looking parts from the 2 generations that wouldn't perform right.
I use one of those clear plastic parts boxes: Upper level is small stuff - screws, jets organized by size, secondary rods and vacuum caps.
Way at the back you'll see the little teeny drill bits and my most clever qjet too ever: a coat hanger. Turns out a bent coat hanger end is the perfect tool for pushing the acceleration pump roll pin out from the inside. Just the right diameter. Bent hanger and a screwdriver to push the roll pin out and you're in business.
Bigger stuff below, primary rods bunched by size in blue tape & labeled to reduce the potential for bending those tiny tips.
Not that often I organize stuff, but this box has saved me hours over the years and made it really fun to work on qjets.
I have a separate box just for gaskets so I can dig in more or less whenever I want to tune and don't worry about ruining an airhorn or throttle plate gasket.
I pulled apart the Everyday Performance built Qjet. Other than choke linkage issues, it has been good for years but is now flooding under hard throttle. Nothing glaringly wrong other than a couple of things. No clip on the needle for the float, maybe the issue. The power piston arm is a little bent, not as severe as Cliff has seen. The power piston spring is stiff but it was tuned for a mild cam. I could not make out what the primary rods were. He did put in a decent accelerator pump.
I did some more cleaning last night and soaking till this evening. I will be doing doing rough measurements to see how much Everyday Performance opened up the restrictions. Whatever Ken opened up, the idle went from Super Lean to slightly rich. I am putting the original size 73 jets in, I put 72 jets in before sending to Ken. Also using Orange power piston spring and Cliff's 44 rods he sent, factory were 44K. There is some play in the primary bushings so I will do them and a new air door cam and spring, otherwise Ken's idle calibration should be close enough. The wideband going on the car for the new motor will really tell the story.
Last edited by olds 307 and 403; June 15th, 2021 at 06:14 AM.
I changed the air door cam and spring, there was some wear.
I also opened up behind the idle mixture screws, Ken opened them around .075, Cliff suggested .080 to .100" depending on calibration. I upped them to .092" size drill bit, next size was around .074". I am not adding bypass air, I am keeping the hot air choke and using the Performer manifold with a 1" open spacer. The RPM intake is probably better choice but I don't want this Performer sitting on the shelf. I pulled the primary throttle shafts, there is bronze bushings in the primary side. They don't look too worn, not sure I want to fight them out. There is minimal play, the new bushings look the same size and slop as what is in there. The idle and main air bleeds, all 3 are around .070". I will try and measure the idle tubes and idle channel restrictions tomorrow.
Well, I did a couple more measurements. It is hard to tell the idle tube size but Ken enlarged the idle channel restrictions to around .055" right around where Cliff suggests. My .092" holes behind the mixture screws didn't hurt a thing, helped if anything. I also installed 73 primary jets and Cliff's 44 primary rods, I had the APT set at 7 turns from seated, I went to 8. I set the float at 1/4" drop per Cliff's suggestion. I think this carb was dropped on it's side at one point and slightly mushroomed where the bolt goes in for the choke housing. It causes the housing to pull too tight against the main body. I added a small washer between the housing and main body. I used the linkage Cliff sent me the rod from the pivot link in the main body was bent and not allowing full choke closure. I went to start it, it fired right up, the choke linkage stuck on. I backed the screw off a hair on the choke housing, seemed to fix it. It definitely idles smoother in gear. I turned the idle mixture screws 2.5" turns from seated and never touched them after. Flooring it or anything over half throttle caused stalling and flooding out, no longer. The air door needs tightened up a bit but much better, just a slight bog. Once I get my wideband I can it bang on for the new 358.
I0 surprised at 73 jet. I'm 68 jet and fussed with APT and went from 9 to 11.7 mpg and this is an 800 quad. Maybe I should try this set up to see if it helps.
This was a 78 403 Qjet that ran terrible when I bumped the compression on my 350 from 8 to 9.6 to 1. I threw 72 jets in it and Ken put in thinner rods with no markings I could read. It ran way better along with the idle recalibration. I will be 9.6 to 1 again with 14 degrees more intake and 4 degrees exhaust with this roller cam.
April 20th, 2021, 10:31 PM
