spekbikes

People look down on quadrajets because they bog, but in actual fact if you know how to tune it! these can be a cheap Very effective carburetor! my local drag racer, has a 350 that looks pretty stock, and it makes 575 hp with a quadrajet that flows 1100 cfm. thats what i said when he told me! 10.06 1/4, no turbo, no nitrous, no super,

i know about modifying the secondary air valve to open correctly, removing an 1/8 of an inch off the accelerator pump, i have heard putting a paperclip under the yoke of the secondary to leave it slightly opened, so when u mash it, the fuel is already there, thus not creating a bog. some tricks work, and some dont, i would like to figure otu which ones are worth trying and not!

thanks

five7kid

iTrader: (14)

There's a local racer that has a '67 Nova 327 that he runs in F/SA on the circuit, and brackets locally (just to stay in shape). It runs 12.2's up here, which is 11.3's at sea level. Since it's a stock class, he has to run a q-jet with the right numbers, etc.

I had a look at it last weekend. He has an adjustment screw in there to adjust the max AV opening. It has a brand new looking choke pull-off on it. Otherwise, you can't see anything from the outside that looks out of the ordinary. You can be sure it's completely tricked out on the inside, though.

Stick to the stuff you see in the tech article. The choke pull-off, AV tension, and rods/hanger combo are the real keys.

spekbikes

yes, they install a new choke pull off, either u can buy a performance one, or you can drill the opening out, to make the secondaries come in quicker, a stock one takes "3-5 seconds" and a performance one is anywhere from 1 - 2 seconds atleast i read that somewhere, but what i really am after is the internal stuff that these racers do? that way everyone who reads this, will know what works and what doesnt!

i know a few internal holes and what sizes they shoudl be brought up to.
-idle bleed's (frontside base plate) 93 thou (thousandths of an inch)
-idle air bypass (topside baseplate) 135 thou
-epoxy the plugs inside and out the carburetor because they "leak the higher the pressure" (those little round circle things that looks liek a plug.
-i know about 5 more holes to enlarge but they are hard to explain, i can draw a picture for anyone that is intrested? but i know there is more tricks to make these carburetors work, what works for one may not work for everyone but its worth a try, so post your ideas or thoughts.

ksrammstein

not to mention that you can get decent gas mileage

Nitsujx82xZ28

On the subject of gas mileage, how many miles/gallon should a completely stock 305 get with a q-jet? I would assume more than 12 which is what i get when i drive easy.

Fast305

My G20 van got 16 on the highway with the factory 305-700r4 and 3.42:1 gears. That was with the non computer q-jet. It gets 18 with the mods and edelbrock 1405 but has much more power.

spekbikes

i know you should be getting more then 12 if you drive easy with a 305. my guess 15-20 mpg if you had it tuned correctly!

slammnmini

im actually in desperate need of rebuilding my q-jet...i would love to hear some suggestions to turn my carb into something better than a hog! thanks

spekbikes

alright, but first i need to knwo what you have done to your motor! because the tricks i know are based on my motor which is a 350, with a 110 degree , 440 lift cam, ported heads, edelbrock intake, and my q jet up top, but mine is pretty mild little sbc, so i would think yours should run the same, ill email you the pictures of how to do it and what sizes to drill them out to. basically the idea is to enlarge a few holes to create a bigger pumpshot(accelerator pump) and give it more fuel throughout the primary range, so there is no bog when the secondaries open up because of too much of a transition. first off you need a numbered drillbit set down to 40 thoughsanths of an inch, a simple rebuild kit. its all pretty straight forward. but try it on an extra carb, and u dont like making it go fast, just change it back to the stock bogger!

it depends on how much moeny u want to put in the carb
but u have to have atleast a
-drillbit set (down to 40 thousanths of an inch)
-carb rebuild kit
-new performance jets
-epoxy

optional
-edelbrocks accelerator pump(suppsoted to give a bigger shot of gas) (30 bucks canadian)

ridecamro

i just rebuilt my q-jet on a 350 basicly stock motor yeah it bogs when i smash it it use to reall bad till i got it rebuilt and also it idles high what could i do to make more cfm and trick ti out a lil

Fast305

Make sure the vacuum can is holding a vacuum. If the can drops off too quickly it will let the secondary air valves open too soon making the engine bog. I would check the tension on the air valves. The standard setting is about 7/8 of a turn. I would also change the secondary metering rods to DRs and the hanger to a F. I changed an 1988 olds 307 over to Drs and an F hanger and the throttle response was great. Most factory rods are way to lean causing a bog. The cool thing about a 4 barrel like a Q-jet or edelbrock is that you can run the primary side lean (at part throttle) for fuel economy but run the secondary side rich for performance. That way you can have performance as well as fuel economy.

spekbikes

yes u can jsut do a simple rebuild on it! even after i rebuilt my carburetor to stock, it still bogged on my car, thats when i went to my local drag racer and he told me some tricks, he charges 500 bucks for a carb rebuild with most of his tricks! his q jet flows 1100cfm, and makes 575hp, and runs 10.06 no power adder, just 8 or 9 years of working on the same engine to fine tune it!

if you want to know the holes to drill out, and what sizes to brign them up to i iwll email them to you.but keep these tricks to yourself not to your opponent! if you tell everyone they wont be tricks , thats what he told me.

ridecamro

yeah that would be great and my car bogs right when my secondarys open pretty bad to and it wont get up and go even then so i'm slightly confused. like the screw that is attched to the seconday vacum that looks like it controls how much the open up and i don't know were to set it at my cilton don't even tell me and i think that might be the prob i've checked all the vacum lines thier all good. and i just had it ruebuilt so i don't know if my firends dad scrwed up or anything. could u please e-mail me those tricks. ride509@msn.com is my e-mail thnaks man

ljnowell

yay, I like to hear about vans, thats why I'm at a THIRD GEN WEBSITE

Fast305

If you read my post they are Q-jet 305 related. My point is that a Q-jet is a good carb. My point is also that a 305 can get good mileage. In a THIRD GEN it should be capable of averaging 20 mpg consistently. My point is that 12 mpg in an easy driven F-body is terrible. He either drives with his foot on the floor all the time(calling it driving easy) or something is seriously wrong such as a plugged cat, stuck mixture control solenoid, fuel leak, etc.

ljnowell

A lot of people are under the misconception that these cars are meant to be driven hard because they are sports cars. What a load, they are no different than any other car. I knew a kid who burned his tires night and day, and then said how he didnt treat his car too rough, because he didnt drive that fast. What a joke.

Fast305

Agreed

spekbikes

I do agree, it is just a car, but, im not sure how this relates to my post??

anyway, back to carburetor talk... is there anyone else that wants to know stuff or wants to explain what they did?

ljnowell

it doenst relate to your post, it relates to the thread. Its called conversation

my84firebird

I'm getting 10 mpg on my quadrajet. It's the original carb, and i doubt its ever been rebuilt. Car has original LG4 w/105k miles, new : plugs(AC's), wires, cap, rotor (all accell), o2 sensor, temp sensor, flowmaster, open element, no cat. I'm getting ready to buy a replacement carb cuz I'm goin broke just driving to work and classes. I've done some research, and I'm pretty much set on another quadrajet (Summit catalog has them for 359). I'd like to switch it out for a holley or edelbrock but I dont really want to change out the distributor and all that jazz so the torque converter will lock up.

Is anyone else getting 10mpg? or am i the cursed one? In any case I seriously hope a new q-jet will solve that!

my84firebird

I should add that this is with the TPS unplugged. If I plug it in the car idles like crap and runs terrible, unplug it and it drives perfect...

Fast305

You need to either set the TPS or replace it depending on what is wrong with it. Without the TPS the carburetor will run full rich and the distributer will run real weak advance curves. Having the TPS UNPLUGGED will kill your mileage just as you said. That combo should be capable of 20 miles per gallon on the highway with a light foot.

spekbikes

also make sure your choke is adjusted correct! that was my problem lasst year, it was out of adjustment and i got about 10 mpg as well! mine isnt computer controlled q jet so i dunno about the tps, but that was atleast my problem!

SLOWFIVEOH

iTrader: (2)

My Quadrajet is a bigger one off of a Cadillac...My dad tuned and jetted it for me and It pushes 730 cfm...Has electric choke...Starts perfect even in the teens on winter mornings...And have never had a problem out of it....I love it....I've had Holleys and have had less problems out of my Rochester then any of them!

AnotherfastIROC

I've spent a lot of time playing around with the Q-jets on my Olds 307, On a big 98 regancy I was pulling 20-22mpg on the high way. Right now I how an 86 Z28 with a caprice interceptor 350 in it, with the stocker carb that supposedly had been rebuilt right on it I was lucky pulling off 15MPG. I Since I dropped on my Olds carb. I've been pulling 17 city driving and on the last trip to VA I pulled off 24 on the highway at 75 mph. And Like I said thats with a 350, 3.73's, headers, 1.6 ratio rockers, T-5, and a 350. As for performance, It's faster than my 87 IROC with 3.42 700 r4 and all the same parts.

Brent500

I recently installed a personal overhauled 5.7 vortec in me 83 4wd with a quadrajet.I rebuilt carb an beveled secondary av ditched the fuel filter installed carb an putt inline filter with electric fuel pump.I also ditched vaccum break an stock spring installed my own adjustable spring .I also vented float out side air filter because of better pressure differential between float an venturi

Damon

I'd just like to point out that most of the stuff done to ANY carb that's destined for the race track you probably don't want or need for a street driven application. I happen to have a few tricks of my own and I've run QJets down into the 10.9/11.0 range (N/A). My mild little Qjet-equipped 383 blower motor in my sig is good enough for bottom-basement 12s running EXACTLY the same as I run it on the street (literally drive it to the track, makes some runs, drive home). I've worked on them since I was 14. I'm now almost 50, if you want to do the math on that.

Airflow-improvement mods CAN be worthwhile, but they're not where the bang-for-the-buck comes from. Most of the improvement comes from simply having it functioning properly, well tuned for the application and getting full secondary air valve opening quickly but not so fast as to cause a bog.

The QJet follows the 80/20 rule like most things do. You'll spend 20% of the money getting 80% of the improvement. The last 20% improvement costs 80% of the money and is probably not worth the expense for most people's applications.

I would like to see this diagram of what holes to drill, where and how much. Only because drilling things out on a QJet gets dangerous in a hurry if you don't know what you're doing. It's also an ITTERATIVE process. Drill a little larger, test, decide if you need to go further, repeat over and over. Remember that it's virtually impossible to UN-DRILL a hole for the home-gamer.

Though I claim to be the "Last remaining QJet tuner on planet Earth" that's not true. There's probably at least 20 guys better than me at it in the country. But then again, those guys don't give away their secrets for free over the Internet like I do.

w41duvernay

Can anyone here can suggest what rod and jet size I should go with on my Quadrajet. I've got an 86 LG4 Pontiac S/e firebird that has a Comp Cam 260, Edelbrock performer intake, headers (primaries 1.5", collectors 2.5"), and will have a 3" exhaust system behind it. We are trying to make it perform like the same year Trans Am HO 305.

Damon

Still running the computer controlled QJet?

If so, you need a set of DR secondary rods and a J hanger (you may not be able to find that exact hanger but something like a still-available G should do the trick). That's the exact combination that the factory used on the L69 carb. Primary side is identical between them since that's the computer controlled side.

Not sure what you're running for an air cleaner setup, but a stock single snorkel setup like the LG4 came with originally is pretty restrictive when you get to that power level. A simple open element would work best for cheap. You can always swap it out temporarily for the stock air cleaner if you need it to pass visual emissions inspection. Then put it right back on when you get home.

w41duvernay

Yes, I am using the computer controlled Qjet ! Any ideas on what jet size that I should be using to compensate for the Headers and improved exhaust ? Thanks for your help Damon.

norton750

as another old Q-jet man I have to agree with all you say. Be very reluctant to drill the carb. One thing that I have done for years is collect lots of carbs from all sizes and model engine so that I have an assortment of parts.