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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
I am searching for posts on converting my 87 Formula Firebird from the Electronic Q-Jet to a different carb, something that an absolute amateur can do in the garage. I am replacing the 305 with a mild 383-hydraulic roller cam engine for low end torque for street use. Fuel injection is not out of the question if it is truly a plug and play design. Thank you.
Also in support of sticking with the Q-Jet here. Set one up that has gone 12s in the Monte Carlo SS it is in.
The computer only controls the air/fuel mixture on it at part throttle. At WOT it functions as a standard Q-Jet. You can jet the primaries and secondaries up to match the fuel demand as well as recalibrate many of the internal passageways.
The engine in the Monte Carlo SS was built to make about 425 hp with a pretty mild cam.
One of my concerns is that I know nothing about adjusting a Q Jet. And unfortunately, my Q Jet has never been adjusted since I bought the car in Oct 1986 and I changed a number of things(Gale Banks 3'' cat back exhaust, 1.7 ratio rockers, chip, etc.)not knowing if it actually helped. That's why I wanted to have "a fuel system for dummies". I have yet to find anybody in my area that wants to work on the Q Jet: everybody tells me to ditch it for EFI or a more traditional spread bore Holley type carb. I appreciate your suggestions...
One of my concerns is that I know nothing about adjusting a Q Jet. And unfortunately, my Q Jet has never been adjusted since I bought the car in Oct 1986 and I changed a number of things(Gale Banks 3'' cat back exhaust, 1.7 ratio rockers, chip, etc.)not knowing if it actually helped. That's why I wanted to have "a fuel system for dummies". I have yet to find anybody in my area that wants to work on the Q Jet: everybody tells me to ditch it for EFI or a more traditional spread bore Holley type carb. I appreciate your suggestions...
So you'd rather learn about a different carb that has to be modded in, as opposed to learning the one that's there? People are afraid of qjets because of lack of knowledge and then those with no knowledge spread word that qjets suck. Those same people probably can't tune a Holley either but they think they know because they pulled it out of the box and it worked. By all means, a qjet isn't anymore complicated in tuning than any other carb. Trial and error to see results is all the same.
My suggestion is to learn about the qjet. https://cliffshighperformance.com/ has information, an excellent book, parts and an expert to actually talk to on the rare occasion that comes up.
And if not, learn about whatever else you put on there. Learn a Holley or fuel injection. Any mechanic you pay to do it needs to be specialized and pricey in anycase. If you're physically capable of doing the work then why pay someone?
“something that an absolute amateur can do in the garage”
alice missed this part.
I don’t recall Cliff’s book saying how to tune an E4ME.
You’re carb might need a rebuild to include repair of worn shaft bushings. I’ve read a lot about these carbs, and recently had mine rebuilt by one of Cliff’s former employees. But I still need to do a lot of relearning to get it tuned on my car. You might be able to figure it out. But it’s not overly simplistic as alice implies. Don’t give up yet though.
An old Q-Jet can be a witch with a capital B to get working right again.
Notable among the problems I've experienced have included such severe dissimilar-metal electrolysis around the needle seat that gasoline could permeate the casting around the threads; cracked fuel inlets (fuel filter housing, if you will) that it was impossible to tighten up the 1" nut; damage to the rear surface of the top of the secondary venturis from overtightening the 2 rear air horn to throttle plate screws; and so on.
It's very easily possible for these carbs to have problems that no backyarder like me can fix. Time was, it wasn't that big of a deal, you could go to the junkyard and get more cares; but those days are long gone now.
That said, the Q-Jet is one of the best carbs ever built, for a street car. If one of em works right, it's REAL hard to beat, especially for a driver. On a racer, maybe it's not the top performer, in terms of power (which is to say, if somebody got their car into the 12s with a Q-Jet, it's not out of the realm that some other carb would get it DEEPER into the 12s, or maybe even the 11s); but for a street driver, it's almost impossible to beat.
Of all the carbs that you could put on one of these cars, the Edelbrock has GOT TO BE the worst choice. NOTHING about it fits right. Fuel lines, throttle linkage, air cleaner, and so on; EVERY detail about those, fights back, They're just too "universal".
For my money, the best carb you could use, if your Q-Jet is beyond salvage, is a Holley 6210. 650 spreadbore mech sec double pumper with the fuel line in THE RIGHT PLACE for a Q-Jet equipped car; throttle linkage options that can be made to work RIGHT with parts you can actually just go to the store and buy; VAST tuning ability; EXCELLENT gas mileage capability, not as good as the Q-Jet's, but MUCH better than the Edelbrock; and various other worthwhile advantages and features. Q-Jets are not hard to tune, once you understand how they work, which is different from many other carbs; but parts are getting harder to source, and lots of the things that sometimes need to be done, like drilling out passages that are deliberately restricted so that there's NO WAY they can EVER fail emissions mandates, require tools that are ... not exactly off-the-shelf. No matter what "Fastxxx" claims to have done. While I don't want to call him a liar, he's well and widely known for being rather ... too ... enthusiastically generous to himself ... about his claims. Smart guy, knows his poop, but tends to make claims that don't align with the known laws of physics that evidently apply throughout the universe except in his garage, and ESPECIALLY seem to allow exemptions for vans.
DON'T go with an Edlebrock. Either repair your Q-Jet, or get a 6210.
Keep in mind, you'll have to replace the dist with a vac adv one, and do something creative about the TCC, no matter what non-computer carb you use as a replacement. It's not as simple as just swapping out that one thing.
What I see in that photo doesn't look too bad. If somebody brought that to me, I'd sure as hell try to fix it, LONG BEFORE I'd yank it and swap it. That carb will work fine on a 383 if the cam gives similar idle vacuum to the OE 305, with minor tweeeeks that you can do in your garage. Don't give up on it without at least giving it an honest try first.
“something that an absolute amateur can do in the garage”
alice missed this part.
I don’t recall Cliff’s book saying how to tune an E4ME.
You’re carb might need a rebuild to include repair of worn shaft bushings. I’ve read a lot about these carbs, and recently had mine rebuilt by one of Cliff’s former employees. But I still need to do a lot of relearning to get it tuned on my car. You might be able to figure it out. But it’s not overly simplistic as alice implies. Don’t give up yet though.
Cliffs book has alot of good information that does carry over well. Walks you through all the basics minus the CCC stuff. That being said, Doug Roe's book I borrowed from the local library had a good section on CCC theory and adjustment. Combine the two books to learn how it all functions and works and its not hard to fill in the overlap of the two designs. As I said earlier the CCC mixture control solenoid is just an evolved power piston so to speak. Once it is dialed in appropriately, the jets and passageways are correct for the application and you set the mixture control adjustments it doesn't care if it is on a 140 hp 307 Oldsmobile or a 500+ HP 454. If the cam makes good vacuum the CCC feedback will work with either engine.
“something that an absolute amateur can do in the garage”
alice missed this part.
I don’t recall Cliff’s book saying how to tune an E4ME.
You’re carb might need a rebuild to include repair of worn shaft bushings. I’ve read a lot about these carbs, and recently had mine rebuilt by one of Cliff’s former employees. But I still need to do a lot of relearning to get it tuned on my car. You might be able to figure it out. But it’s not overly simplistic as alice implies. Don’t give up yet though.
My apologies if I sounded like it's overly simplistic. We WERE or ARE all absolute amateurs at one point. But we learned. I was trying to imply to learn whatever goes on the engine. I feel if you truly learn a Holley then you can truly learn a qjet. I don't doubt it's easier to get "close enough" with a Holley or get there by accident. And there's nothing wrong with a Holley. Or switching to an aftermarket efi. But regardless an absolute amateur would have to learn to swap those out too. Which is easier for the OP? I don't know, but I wanted to give the OP some confidence that it can be done with a qjet without a paid professional to do it.
The easiest option is the keep the Q jet talk to cliff and retune for the engine. I would consider sniper EFI if you are considering swapping but it will be more expensive. Edelbrock carbs are OK and it will run but vs EFI or Q jet they are very lacking. Any other carb and you will need to swap the distributor and do something for the torque converter lock up.
When I got my car it came with a edelbrock carb on a swapped 350 after years of tuning with an A/F gauge and vacc gauge in the car I had it running and starting what I considered very good. 10 miles of letting the sniper self tune and I realized edelbrock should have been tossed years ago.
The easiest option is the keep the Q jet talk to cliff and retune for the engine. I would consider sniper EFI if you are considering swapping but it will be more expensive. Edelbrock carbs are OK and it will run but vs EFI or Q jet they are very lacking. Any other carb and you will need to swap the distributor and do something for the torque converter lock up.
When I got my car it came with a edelbrock carb on a swapped 350 after years of tuning with an A/F gauge and vacc gauge in the car I had it running and starting what I considered very good. 10 miles of letting the sniper self tune and I realized edelbrock should have been tossed years ago.
For reliability would take the Q-Jet over any aftermarket garbage EFI system. They run the EFI system a couple of years then discontinue and move on to something different. After a couple of years parts dry up and you can no longer service them. PURE JUNK unless you want to buy a new system every 4-5 years. Better off going with a factory based controller and port fuel injection intake. Like an 0411 PCM on a MPFI holley intake using a 24x ignition or Vortec distributor.
Going with something the factory made millions of practically gurantees someone will make the parts for a long time. Versus a limited run of pure garbage aka Holley EFI.
My buddy ran into this problem with an Edelbrock kit a few years ago. Used a special built Magnetti Marelli controller that Edelbrock discontinued. When it died he was faced with the buy a new kit or retrofit controllers. Edelbrock wanted a ton of $$$ for a new controller and harness. We converted it to an 0411 and picked up a GM to Ford IAC adapter. Installed a customized factory 0411 based harness and an EFI connection 24x reluctor using a vortec van distributor for a cam sensor. Sensors are now all GM as is the PCM. At the same time he had a 4L80E built to replace the weak 700r4. It is a completely different truck with the reprogrammed GM PCM running the engine and trans.
My old G20 van, my 99 Tahoe and my 97 Express van are all factory based EFI. I would not bat an eye twisting the key and driving any of them to Alaska and back. Local parts availability is not a problem for any of them. With Holley I would be stuck somewhere for maybe a week or more waiting on some replacement part to arrive if something gave up the ghost on the trip. Not so with the factory based stuff. Case in point, in 2015 with the cammed, aluminum head, L31 marine intake and coil per cylinder ignition running with an 0411, with my brother as a co-driver drove the 97 Express from Fort Worth, TX to upper Ohio and back in 52 hours round trip. Rained on us 2/3 of that trip and the weather was in the 30s and 40s. Burned a plug wire around Memphis on the way home (could intermittwntly feel a cylinder dropping) that showed up as a horrible misfire in absolutely pouring rain around Little Rock prior to a fuel stop. Let it idle while pumping gas, engine smoothed out but still had a slight misfire that cleared up after we stopped a few hours and left the engine idling to keep the heat going. After the massive flooding rain stopped about 4 hours later and it was daylight again we took off for Texas. Was an un-eventful 2,200 mile trip that resulted in the replacement of 1 plug wire and had to add 1 quart of Mobil One 5w30 when I got home. Averaged 18 mpg for the whole trip, most of which was run between 75 and 90 mph. I think the header heat running 90 mph and beyond for ~3 hours straight between somewhere north of Nashville and west of Memphis when the rain stopped and the roads were dry on I-40 claimed the plug wire.
Will the stock air cleaner fit on the Holley spreadbore carbs? Does the stock TV cable bracket work with it?...
My gut says the stock air cleaner will fit given both have a 5-1/8" opening. As for the TV cable, probably need to pickup a geometry adapter and good to go.
04-23-2021, 09:37 AM
