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Old 10-07-2018, 02:33 PM   #1
Greasey Harley
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Wanna-be Quadrajet guru

I recently picked up a new hobby.
I decided that I want to be "That Guy" when it comes to quadrajets.
A buddy of mine gave me about a dozen Q-jet cores that he had lying around and that sparked my interest.

Armed with these cores, A book by Cliff Ruggles, some papers by Lars Grimsurd, some precision drill bits, an ultrasonic cleaner, and a Genuine "Barker Un-warping Tool" I think I stand a decent chance of actually tuning some Rochesters.

I have successfully rebuilt about a dozen marine Qjets, when I had my boat repair shop. That's not the problem. I want to figure out how to re calibrate carbs that were choked down by the EPA and make them actually preform for a given application.
The first victim is already on the bench
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Old 10-07-2018, 05:03 PM   #2
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Re: Wanna-be Quadrajet guru

Good hobby, hope you figure all out.
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Old 10-07-2018, 05:29 PM   #3
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Re: Wanna-be Quadrajet guru

Sounds like a plan.
Keep us posted.
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Old 10-07-2018, 05:31 PM   #4
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Re: Wanna-be Quadrajet guru

Even though there's a lot of older cars that still use carburetors, it's getting hard to find good carb repair shops these days. I started doing my own repairs on them because there weren't any carb shops around here.

It may not make you rich but it's a good hobby to get into.
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Old 10-07-2018, 05:59 PM   #5
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Re: Wanna-be Quadrajet guru

I kind of enjoy working on Quadrajets! The best tool I've found is a good magnifier with a bright light and a eye loupe. It really helps looking into all of the passages to make sure they're clean.
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Old 10-07-2018, 06:44 PM   #6
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Re: Wanna-be Quadrajet guru

And crack detection spray for the float bowls ��
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Old 10-07-2018, 06:48 PM   #7
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Re: Wanna-be Quadrajet guru

Just joking love the quadrajet I’ve been messing with mine for ages it was flooding turned out it wasn’t the poor carbs fault like everyone was saying. I had too much fuel pressure from the mechanical lift pump causing fuel to force past the float needle. These quadrajets get the blame for everything lol
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Old 10-07-2018, 07:27 PM   #8
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by Troy Sr View Post
I kind of enjoy working on Quadrajets! The best tool I've found is a good magnifier with a bright light and a eye loupe. It really helps looking into all of the passages to make sure they're clean.
When I replace the strings on my guitars I save clipped pieces to clear small passages in the carbs. I cut them 4-5 inches long and have some from the thicker E string to the thin E string.

Here's a video of another person that also uses them:
https://www.youtube.com/watch?v=duO82KYHTPg
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Old 10-07-2018, 11:29 PM   #9
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Re: Wanna-be Quadrajet guru

That's good to hear that someone local is going to get into something 'old school'. Hopefully you have better luck than me with attracting local customers.
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Old 10-08-2018, 01:24 PM   #10
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by Greasey Harley View Post
a Genuine "Barker Un-warping Tool" I think I stand a decent chance of actually tuning some Rochesters.
How much was the Un-warping tool? He doesn't list a price on his site.

Thanks!



j
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Old 10-08-2018, 02:01 PM   #11
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by Greasey Harley View Post
I recently picked up a new hobby.
I decided that I want to be "That Guy" when it comes to quadrajets.
A buddy of mine gave me about a dozen Q-jet cores that he had lying around and that sparked my interest.

Armed with these cores, A book by Cliff Ruggles, some papers by Lars Grimsurd, some precision drill bits, an ultrasonic cleaner, and a Genuine "Barker Un-warping Tool" I think I stand a decent chance of actually tuning some Rochesters.

I have successfully rebuilt about a dozen marine Qjets, when I had my boat repair shop. That's not the problem. I want to figure out how to re calibrate carbs that were choked down by the EPA and make them actually preform for a given application.
The first victim is already on the bench
I've wandered down that road myself lately and have found it to be very rewarding. It's enormously satisfying to get a Qjet to run right, but now I shake my head at all the unnecessary struggles I had with them back in the 80's. They really are excellent when clean, calibrated, and operating within specs. It also really helps now that I'm older to be able to play with a rig that isn't my daily driver required to get me to work in the morning.

So far I've completely relied upon Cliff Ruggles to select and deliver the proper calibration materials such as jets and metering rods. Not the cheapest alternative, but a certain path to success. Really can't say enough good things about that shop, and his forum is an invaluable resource as well.
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Old 10-08-2018, 08:49 PM   #12
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by jeffahart View Post
How much was the Un-warping tool? He doesn't list a price on his site.

Thanks!



j
It was something like $300, I can't exactly remember. I bought it in '08 or '09, It's been a while. They stopped selling them shortly after I bought one.
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Old 10-08-2018, 08:56 PM   #13
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Re: Wanna-be Quadrajet guru

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Originally Posted by Greasey Harley View Post
It was something like $300, I can't exactly remember. I bought it in '08 or '09, It's been a while. They stopped selling them shortly after I bought one.
I see, maybe I'll give him a ring. Does the tool do main body or just air horn? Maybe I could send you some work? I have a main body that needs work, probably the horn too. Been a while since I looked it.


J
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Old 10-08-2018, 08:59 PM   #14
Greasey Harley
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by SilverMiner View Post
I've wandered down that road myself lately and have found it to be very rewarding. It's enormously satisfying to get a Qjet to run right, but now I shake my head at all the unnecessary struggles I had with them back in the 80's. They really are excellent when clean, calibrated, and operating within specs. It also really helps now that I'm older to be able to play with a rig that isn't my daily driver required to get me to work in the morning.

So far I've completely relied upon Cliff Ruggles to select and deliver the proper calibration materials such as jets and metering rods. Not the cheapest alternative, but a certain path to success. Really can't say enough good things about that shop, and his forum is an invaluable resource as well.
Well, like I said, I've rebuilt them and made them work before. I'm excited about recalibrating them and getting them to preform.

You're right about Cliff. He is The Man! A couple things were left out of his book, but that book is an amazing resource. And Cliff is Super helpful.
I have been lurking his forum as well.

Also, Lars Grimsurd's tuning papers are incredibly detailed. He emailed me piles of procedures, specs and tech tips. I am still deciphering some of his info. ...That dude must be crazy smart.
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Old 10-08-2018, 09:02 PM   #15
Greasey Harley
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by jeffahart View Post
I see, maybe I'll give him a ring. Does the tool do main body or just air horn? Maybe I could send you some work? I have a main body that needs work, probably the horn too. Been a while since I looked it.


J
It does the main body and the air horn.
It works pretty dang good. I am happy with it. Last time I spike with Dennis Barker, He didn't seem to have any interest in selling more unwarping tools ... But It never hurts to ask.
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Old 10-08-2018, 09:07 PM   #16
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Re: Wanna-be Quadrajet guru

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Originally Posted by Greasey Harley View Post
It does the main body and the air horn.
It works pretty dang good. I am happy with it. Last time I spike with Dennis Barker, He didn't seem to have any interest in selling more unwarping tools ... But It never hurts to ask.
Thanks. Guess if he doesn't sell them that's OK. I can send him or you my carbs. I have two, one is warped for sure. I need to check the other one too. Anyhow, I want to get them up.


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Old 10-09-2018, 11:16 AM   #17
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Re: Wanna-be Quadrajet guru

Here are 2 guides I've used, but it sounds like I'm far less experienced than you.

http://www.corvettefaq.com/c3/QJetTuningPaper.doc

http://www.vetteclub.org/warehouse/t...ke%20Setup.doc

What I've done with my truck is installed an Air Fuel gauge. This lets me know EXACTLY what the carburetor is doing. No guess work, no going by feel. A cheap simple setup costs like $75. A nice wide band setup costs about $300.

EDIT:
Found another link full of links
https://www.florida4x4.com/tech/quadrajet/index.php
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Old 10-09-2018, 11:41 AM   #18
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Re: Wanna-be Quadrajet guru

good thread with great information
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Old 10-13-2018, 10:46 PM   #19
Greasey Harley
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Re: Wanna-be Quadrajet guru

Update:
I have successfully built a Quadra-jet That idles nice about 700RPM, has zero off idle stumble a broad power band and a seamless secondary transition.

I gotta hand it to Cliff over at cliffshighperformance.com . That guy knows his stuff.

stock Q-jet off a 1979 K10 #17059201

Recalibrated Carb specs:

upper Idle air bleeds ------- .695
lower idle air bleeds ------- .075
idle tubes ---------------- .036
idle restrictions ----------- .052
main air bleed (air horn) -- .0845
idle screw holes ---------- .089
acc. pump discharge holes - .028
fuel inlet seat (no window) - .135
primary jets -------------- 74
primary Rods ------------- 50c
Secondary rods ---------- .057 (DR)
Float level ----------------- 9/16 (Set lower for off road)
APT adjusted per Lars Grimsurd's instructions, APT spring provided by cliffs High Performance.
Secondary air flaps notched for smoother transition, secondary tension spring set to 7/8 turn, .
Modified for electric choke

Tested and adjusted it on my 75 blazer 4x4 :

1987 350 TBI block
72cc Swirl Port TBI Heads
Cast Iron GM Manifold (modified to fit tbi heads)
RV Cam
Factory style HEI ignition
initial timing 13*
total advance not including vacuum advance, 34*
50* total with vacuum advance plugged in
4-speed sm465 Trans 4:10 gears and 32 inch tires

Runs sweet
It is going on basically the same setup, except with flat top pistons, 9.25:1 Compression instead of 8.75:1, and 3.73:1 gears rather than 410s
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Old 10-13-2018, 11:55 PM   #20
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Re: Wanna-be Quadrajet guru

Only 13 initial.
Should be able to crank that up, don’t you think.
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Old 10-14-2018, 12:12 AM   #21
Greasey Harley
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Re: Wanna-be Quadrajet guru

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Only 13 initial.
Should be able to crank that up, donít you think.
Seems happy there.
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Old 10-14-2018, 12:16 AM   #22
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Re: Wanna-be Quadrajet guru

But it might be totally ecstatic at 18.
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Old 10-14-2018, 12:29 AM   #23
Greasey Harley
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Re: Wanna-be Quadrajet guru

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But it might be totally ecstatic at 18.
I am more concerned with total timing. 34-36 without vacuum advance is about optimal.(or so I am told)
I could recurve my dizzy I suppose, but it seems to run great right where it is. Any more adv. and it might ping under WOT, when it gets warmer. I could probably bump it a couple degrees, but it is an old plow truck. It's fine.

Last edited by Greasey Harley; 10-14-2018 at 04:14 AM.
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Old 10-14-2018, 08:55 AM   #24
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Re: Wanna-be Quadrajet guru

And that’s the safe way to do it!
Setting your timing by following the all in idea works great at up to 1000 foot elevation. Once you start getting up higher you need to rethink your timing and jetting. You need more initial to start the burn earlier and leaner jetting. Most people do nothing about either one and wonder where the power went.
You’re optimizing your carb, I just thought you’d optimize your timing too.
Optimized timing could totally change your carb settings.
But like you said, it’s just an old plow truck.
Best to time it conservatively.
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Old 10-14-2018, 01:29 PM   #25
Greasey Harley
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Re: Wanna-be Quadrajet guru

Quote:
Originally Posted by rpmerf View Post
Here are 2 guides I've used, but it sounds like I'm far less experienced than you.

http://www.corvettefaq.com/c3/QJetTuningPaper.doc

http://www.vetteclub.org/warehouse/t...ke%20Setup.doc

What I've done with my truck is installed an Air Fuel gauge. This lets me know EXACTLY what the carburetor is doing. No guess work, no going by feel. A cheap simple setup costs like $75. A nice wide band setup costs about $300.

EDIT:
Found another link full of links
https://www.florida4x4.com/tech/quadrajet/index.php
A lot of info there, Thank you.
I especially like the diagrams in this link:
https://www.hotrodders.com/forum/qua...ed-451098.html
It was found in the bottom link you provided.
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