Carburetor fun: Rochester Vs. Edelbrock?

[Love 70 Chevys]

Go Rochester. Partial for one reason only...I've lived here all my life. The plant they were made in still stands and produces fuel rails for GM an others as we speak. Still know some old timers who worked the line back in the day. I remember touring the plant back in high school and they were using early robotics to "auto tweak" things. Good memories.

[GASoline71]

I would use a worn out Q-jet before I would use any Edelbrock carb.

I'm a dyed in the wool Holley guy... but still love a properly rebuilt and tuned Q-jet.

Gary

[Steeveedee]

To add to my previous post- the Q-Jet is a TON simpler than those 4GC Rochesters I cut my teeth on when rebuilding them in the '60s. Take off the air horn and turn it over, and HOPE you can figure out where all those check balls and springs came from, with that fuzzy 10th generation photocopy of the exploded diagram, when you're only 16 and it's your first carb overhaul.

[GRX]

Dislike Edel carbs. Especially some of the AFB clones which have no adjustment for the secondary flap opening rate without disassembly.

So, yet another vote for the Quadrapuke. Only say that because like many, I endured years disdain & snide remarks.

The later models are my favorites too. Some time around 74-75 they moved access to the APT from the baseplate to the top. Replace the press-in plug with thread type and you are good to go. 800-cfm models can be identified by bulges in the primary venturi. May be mistaken, no chevy motors ever got those. Look toward large displacement BOP&C engines.

[toolboxchev]

The only advantage of the Eddi is the simplicity. They are easy peasy to tune. Plus you get the option of a manual choke.

Not so for the Quad, even though I would rather have one. I missed that ole air whipping vacuum slurp when I hit the throttle.

[El Dorado Jim]

Originally Posted by 52napco

Seems the consensus is keep the Qjet....Which im0 is the only way to go. I have all mine restored by Bob Stone in PA. It's the best $250 you'll ever spend. I've got several Edelbrock
I'll send you for free..... I personally have never had any luck with them.

send me your edelbrocks,I love them, have them on four of my trucks and they run great,easy to rebuild, rebuilt one that a friend gave me and it is on my 72K20 ,bought a book and was real easy...although I like the q-jet I l have on my 74K20 with a 454...it has been great and has been on the truck since 1995 when I installed the 454,carb is still working great,so no reason to change it, I may try and rebuild it when it is time...

[El Dorado Jim]

Originally Posted by Steeveedee

When you do go to rebuild your Q-Jet, get Cliff Ruggles' book, and get the rebuild kit from him, too. On my truck, the cam that lifts the metering rods on the secondaries broke (dropped down inside the well where it lives, not into the engine). His kit will have that cam, and a new float and accelerator pump diaphragm that resist ethanol. Best kit I ever bought. It even has a new secondary air valve spring, which can get old and not work as well. That MIGHT have been extra; its been a few years since I rebuilt mine. The truck starts and runs like a champ with the original carburetor. I took the throttle plate to a local carburetor guy to get the bushings for the throttle shaft. $50 got all four bushings (though putting bushings in the secondaries is kind of pointless). If you have the time, you can send your carb to Cliff. He has a long waiting list, though- last time I checked, it was a year- but that may have changed. If you give him the information on the engine, trans, etc., he can calibrate it for you. The thing is, with a carburetor that old, someone may have been into it, changing jets and metering rods, springs, etc. Cliff can make that all correct, or properly modify it for your application.

I guess you can tell which way I vote! I've had Edelbrocks and haven't been all that pleased with the longevity- they needed the throttle shafts repaired much sooner than my Q-Jet. That carb got the bushings at about 212,000 miles.

I just ordered Cliff's book from Amazon, I love my edelbrocks, but I also have a quadrajet I love on my 74 K20 that I will try and rebuild when the time comes...I just bought an old 69 GMC motorhome that one of the previous owners installed a 454 with a q-jet on it, it wouldnt run,I threw an old holley on it that is my sons, wouldnt run good on his truck so put an edelbrock on his..I stuck the holley on the motorhome just so it would run...I will try and rebuild the q-jet from the motorhome and see what happens...thanks for the info..

[GASoline71]

While digging for an old article from the late 1990's that I used from 4-Wheel & Offroad magazine on rebuilding the Quadrajet carb I found some good stuff. I had a 1979 GMC K2500 with a really snotty 355 in it. I rebuilt the Q-jet using the step by step process from the above magazine. It was a great how-to by that rag and I wish I could find it again.

But this website from a Florida offroad group has a LOT of info on Quadrajet and other carbs as well.

https://www.florida4x4.com/tech/quadrajet/

Gary

[SonomaComa]

Originally Posted by 68is4me

I also vote quad, But before you get to crazy on the carb what is it doing, are you even sure it is a carb problem? Timing, vacuum leak, bad wires and plugs could all make you think the carb is bad. I would 1st get it nailed down to make sure that it is actually a carb problem.

But on a side note I did do the cliff ruggle's book and the kits from him. Rebuilt it myself but it does get rather expensive if you don't have all the tools to do it right, jewelers bits, vacuum gauges, small punches, small grinders and lots of patience. At least after buying all the correct tools I can build more if I have to.

I have a Casting Number 7029207.
Sometimes when I punch it the secondaries will not open. One time I was driving it pretty good on the freeway and up a few slight hills, and when I got off it died coming to a stop light. It started up right away but then died again when turning into a driveway bout a minute later. Both times I smelt gas. My girlfriend said it even happened to her driving in town.
The timing is 8 BTDC. It sill has the original air pump on it! It has one vacuum line going to it from the right side of the carb. Maybe I should disconnect it and plug up that vacuum line.

[geezer#99]

Originally Posted by SonomaComa

I have a Casting Number 7029207.
Sometimes when I punch it the secondaries will not open. One time I was driving it pretty good on the freeway and up a few slight hills, and when I got off it died coming to a stop light. It started up right away but then died again when turning into a driveway bout a minute later. Both times I smelt gas. My girlfriend said it even happened to her driving in town.
The timing is 8 BTDC. It sill has the original air pump on it! It has one vacuum line going to it from the right side of the carb. Maybe I should disconnect it and plug up that vacuum line.

Or maybe you should find out why it's flooding.

[68is4me]

Originally Posted by SonomaComa

I have a Casting Number 7029207.
Sometimes when I punch it the secondaries will not open. One time I was driving it pretty good on the freeway and up a few slight hills, and when I got off it died coming to a stop light. It started up right away but then died again when turning into a driveway bout a minute later. Both times I smelt gas. My girlfriend said it even happened to her driving in town.
The timing is 8 BTDC. It sill has the original air pump on it! It has one vacuum line going to it from the right side of the carb. Maybe I should disconnect it and plug up that vacuum line.

Don't remember what you are running for a motor, But I would jump timing up to 10-12 and all in at 32-36. But I am no timing expert.

If your secondary's aren't opening that usually an adjustment issues. Is the choke all the way open when it is warmed up? The secondary's will only open when the choke is all the way open. Are the choke pull offs working?

When it quit running could be possible that you choke is not open all way and allowing it to flood on deceleration. When you shut the truck off look down the carb and see if you see any fuel dripping down. Could also be a float issue.

[El Dorado Jim]

I just got my Cliff Ruggles book, wow there are alot of parts and different little adjustments to be made...I love my edelbrocks for their simplicity and ease of rebuilding, I may not try rebuilding a q-jet after all

[SonomaComa]

Originally Posted by 68is4me

Don't remember what you are running for a motor, But I would jump timing up to 10-12 and all in at 32-36. But I am no timing expert.

If your secondary's aren't opening that usually an adjustment issues. Is the choke all the way open when it is warmed up? The secondary's will only open when the choke is all the way open. Are the choke pull offs working?

When it quit running could be possible that you choke is not open all way and allowing it to flood on deceleration. When you shut the truck off look down the carb and see if you see any fuel dripping down. Could also be a float issue.

The choke opens. I was adjusting the idle air fuel mixture and it was open. But when trying to adjust it I would screw one all the way in untill the engine started to slow down. Then I backed it out but the engine never slowed down again. I was afraid the screw was going to come all the way out. What's up with that? There is a knowledgeable guy on youtube about Q-jets, its WhoSaidTyler. Lots of good info there.

[geezer#99]

Originally Posted by SonomaComa

The choke opens. I was adjusting the idle air fuel mixture and it was open. But when trying to adjust it I would screw one all the way in untill the engine started to slow down. Then I backed it out but the engine never slowed down again. I was afraid the screw was going to come all the way out. What's up with that? There is a knowledgeable guy on youtube about Q-jets, its WhoSaidTyler. Lots of good info there.

The mix screws only need to be about 1 1/2 to 2 turns out. Just enough to produce a smooth idle. Turning them in leans the idle mixture, turning them out richens it. You can only richen it so much. Screwing them out further does nothing.

[El Dorado Jim]

Originally Posted by SonomaComa

The choke opens. I was adjusting the idle air fuel mixture and it was open. But when trying to adjust it I would screw one all the way in untill the engine started to slow down. Then I backed it out but the engine never slowed down again. I was afraid the screw was going to come all the way out. What's up with that? There is a knowledgeable guy on youtube about Q-jets, its WhoSaidTyler. Lots of good info there.

you have a vacuum leak

[SonomaComa]

Originally Posted by geezer#99

The mix screws only need to be about 1 1/2 to 2 turns out. Just enough to produce a smooth idle. Turning them in leans the idle mixture, turning them out richens it. You can only richen it so much. Screwing them out further does nothing.

Ok, thhanks.
Here is how I tried to adjust it
https://youtu.be/XRCUibTkm3o