Edelbrock 1906 AVS2 Swap for QuadraJet 750 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 01-13-2020, 11:18 AM
boneste624's Avatar
Registered User
 
Join Date: Apr 2019
Location: Los Angeles
Posts: 54
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Edelbrock 1906 AVS2 Swap for QuadraJet 750

So was at the junkyard the other day and came across a 78 camaro with a 350 and QJ that was rear ended and looked like it sat for a long time. I have read that these are great performers but don't know much about them. Here is the carb. Paid 60 bucks. Are these simple carbs to rebuild and get running great or should I just stick with the eddy? If it's worth the trouble does anyone know a good shop that can do a rebuild? I like old school look so I want this carb.
Attached Thumbnails
Click image for larger version

Name:	IMG_20200112_142450_678_1578935430030.jpg
Views:	32
Size:	63.3 KB
ID:	451129   Click image for larger version

Name:	20200112_141501_1578935446694.jpg
Views:	30
Size:	41.3 KB
ID:	451131   Click image for larger version

Name:	20200112_141446_1578935801097.jpg
Views:	32
Size:	42.0 KB
ID:	451133   Click image for larger version

Name:	20200112_141429_1578935835195.jpg
Views:	15
Size:	41.7 KB
ID:	451135   Click image for larger version

Name:	20200111_171249_1578935881963.jpg
Views:	17
Size:	31.5 KB
ID:	451137  


    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-13-2020, 12:18 PM
Registered User
 
Join Date: Apr 2007
Posts: 12,732
Wiki Edits: 0

Thanks: 240
Thanked 1,249 Times in 991 Posts
These are nice carbs but not somehing you just go exploring in without first picking up a book or two see link for examples.

https://www.amazon.com/s?k=quadrajet...l_786xn8oqey_e

These are spread bore carburetors which will not bolt to a square bore intake that fits the standard Edlebrock or Holley intake without an adapter.

The carb you picked up will be a California emissions model it will take some additional work to bring it up to performance standards but again you need to read up on these and get familiar with them they are a bit of a different beast. Quite different from Holley fare somewhat more related to what you see with your Edlebrock, especially the AVS. Also, the old Carter Thermoquad is a spread bore and is rather similar in complexity to the QJet.

As a note the Edlebrock carburetors are a continuation of the Carter AFB and AVS. Edlebrock having made some improvements along the way especially to metering. The AVS2 introduces the Ford/Holley style annular boost venturi in the primaries along with the metering rod variable jet size that results from runnng a metering rod inside a jet bore which is also common to the QJet.

As for performance, I've used both over my decades, in terms of power, driveability, and mileage they are more similar than different, especially when comparing the AVS or AVS2 and especially the Thermoquad to the QJet. For tunability especially with a high strung engine and absolute best top end power not much can take on a Holley, but the tunability of a high end Holley is wasted possibilities and money on a mild engine, on the street it takes a lot more work to get the kind of overall performance from a Holley that the Edlebrock or well restored QJet just delivers especially in miles to the gallon.

Bogie
Reply With Quote Quick reply to this message
The Following 2 Users Say Thank You to BogiesAnnex1 For This Useful Post:
AutoGear (01-15-2020), techinspector1 (01-13-2020)
  #3 (permalink)  
Old 01-13-2020, 02:35 PM
techinspector1's Avatar
Member
 
Last wiki edit: DynoSim combinations
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 77
Posts: 17,063
Wiki Edits: 326

Thanks: 1,966
Thanked 2,871 Times in 2,146 Posts
In my opinion, Cliff Ruggles is the GO-TO guy for Quadrajets. I would read his book first. Doug Roe's book did not work well for me.
Reply With Quote Quick reply to this message
The Following User Says Thank You to techinspector1 For This Useful Post:
eric32 (01-14-2020)
 
  #4 (permalink)  
Old 01-13-2020, 03:21 PM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: Found an LQ9 today
Join Date: Dec 2005
Location: Carlisle, PA
Age: 46
Posts: 5,546
Wiki Edits: 16

Thanks: 32
Thanked 65 Times in 54 Posts
Qjet is light years better than an Edelbrock. I won't get on my soapbox, but good for you.

I would say Qjets aren't the easiest to rebuild, but nothing special about tearing into one. Whatever you do, I strongly suggest not using an adapter to put a spreadbore carb on a squarebore intake. It will never work the way you want it. The primaries will go from tiny to huge and kill velocity, and the secondaries will go from huge to small and kill flow. Make sure the intake you use is either a spreadbore intake, or a dual-fit type.
Reply With Quote Quick reply to this message
The Following User Says Thank You to curtis73 For This Useful Post:
joe_padavano (01-21-2020)
  #5 (permalink)  
Old 01-13-2020, 06:25 PM
techinspector1's Avatar
Member
 
Last wiki edit: DynoSim combinations
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 77
Posts: 17,063
Wiki Edits: 326

Thanks: 1,966
Thanked 2,871 Times in 2,146 Posts
Here's the best street intake manifold for your Quadrajet, a tall dual-plane. I know it's a little pricey, but it's the best. Note the carb pad height, tallest one available for budget money. I think Chevrolet Performance has a taller one, but the price is pretty tall too......
https://www.summitracing.com/parts/edl-7104?rrec=true

Here's another lesser-known manifold with a tall carb pad height for less money......
https://www.summitracing.com/parts/s...make/chevrolet
Reply With Quote Quick reply to this message
The Following 2 Users Say Thank You to techinspector1 For This Useful Post:
AutoGear (01-15-2020), eric32 (01-14-2020)
  #6 (permalink)  
Old 01-14-2020, 09:22 PM
55 Tony's Avatar
Registered User
 
Join Date: Nov 2018
Location: Cocke County, TN
Posts: 1,199
Wiki Edits: 0

Thanks: 139
Thanked 209 Times in 185 Posts
It may or may not be one of the better ones. A good picture down the primaries with the choke open would help. Better yet with the choke and the primaries open and light shining clear through. I agree, Cliff Ruggles literally wrote the book on Q-jets. Buy his book.
__________________
Young enough to learn ... too old to remember.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-15-2020, 11:07 AM
Registered User
 
Join Date: Jun 2010
Location: Syracuse, NY
Posts: 4,826
Wiki Edits: 0

Thanks: 4,183
Thanked 929 Times in 758 Posts
whats wrong with the brand new avs2, something other than it says Edelbrock on it?
Might be less work to put a kit in a brand new AVS2 with annular boosters, than worry about unscrewing all the wrongs in a smog-era Qjet, bushing throttle shaft bores, correcting a warped baseplate and trying to patch up leaks in the main body.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 01-15-2020, 02:25 PM
Registered User
 
Join Date: Jun 2010
Location: TX
Posts: 4,027
Wiki Edits: 0

Thanks: 41
Thanked 484 Times in 453 Posts
The good Rochester Q-jet carburetors are the 1966-1970 models. They do not have the later model bogus EPA adjustments.

The rebuildable 1966-1970 Q-jets are becoming difficult to find. I recently purchased a rebuilt 1970 Q-jet (#7029203) for a 350 Chevrolet engine with a manual transmission. That was used from 1967-1977 on various GM engines.

The Q-jets will last much longer than the old 1962-1966 Carter AFB (aluminum four barrel) 625 CFM carburetors because the AFB were rebuilt to death by 1986. In 1986, I purchased five Holley rebuilt 1962-1966 Carter AFB carburetors from Chief Auto Supply for $25 each without a core charge. Chief was dumping them from their inventory.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 01-21-2020, 10:30 AM
boneste624's Avatar
Registered User
 
Join Date: Apr 2019
Location: Los Angeles
Posts: 54
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by AutoGear View Post
whats wrong with the brand new avs2, something other than it says Edelbrock on it?
Might be less work to put a kit in a brand new AVS2 with annular boosters, than worry about unscrewing all the wrongs in a smog-era Qjet, bushing throttle shaft bores, correcting a warped baseplate and trying to patch up leaks in the main body.
Absolutely nothing wrong with the Edelbrock. Super easy to tune and swap jets, rods, springs etc. Runs perfect no complaints, lots of power and starts right up everytime. Just chasing more horses. So basically what you guys are saying is that I bought a boat anchor? Damn. I'll keep an eye out for the good years. Love the simplicity of a carb setup but also really like the idea of getting in depth with tuning . What do you guys think of swapping out the eddy for a T.B.I. efi? Really want to squeeze as much hp from my setup for now and get familiar with datalogging.
I have a base tune from a 9c1 I'm going to start with.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 01-21-2020, 01:18 PM
Registered User
 
Join Date: Apr 2007
Posts: 12,732
Wiki Edits: 0

Thanks: 240
Thanked 1,249 Times in 991 Posts
Max power and driveability are not the same things. If your engine is a dyno queen designed to deliver impressive to end numbers you build and tune one way. If you're after an engine that isn't a gear shifting war hunting for power peaks on the steet then 'driveability' gets to be a preference. If the engine has a huge displacement stuffed into a light vehicle then even a dyno queen becomes streetable thanks to generous torque that big motors make. If you stuff a smallto modeate size engine into something heavy then driveability gets to be a problem since the torque isn't excessive against vehicle weight and probably gearing should be included in that because the engine gets peaky and to get it to decently you got to drive it on the peaks which usually are far from the rpms used on the street. I'm not saying one is necessarily better but you need to step in to this with eye's wide open as dyno queens are a real SOB to herd.

If you get an aftermarket TBI dialed in well, they tend to show better driveability in the mid range power band than a carb unless you're talking high end Webers. That is a result of production carburetors have a lot of compromises to keep cost down. This is where EFI shines as it does a way better job of mid range fuel tuning for a lot less cost than these high end exotic carburetors. But up n the top end at the power peaks the ability of even a production carburetor to fuel accuratly is very good thus you don't see big differences in top end power between even production carbs, exotic carbs, and EFI. At the top end it's more about air flow throught the throttles and how well the manifold distributes those flows.

Manifolds count for a lot an example on a moderate build Chevy 350 an Edelbrock Performer RPM with a 650 CFM carb will generate the same power as a ProComp intake with a 750 CFM carb. Put an aftermarket TBI on either of those and not so much. These TBI's really like an open plenum, whether that's a dual plane with the divider milled out or a single plane with an open plenum, this is where they are happier.

I guess the real answer is you can't just make power by simply sticking highly regarded parts on in a random order.

Bogie
Reply With Quote Quick reply to this message
The Following 2 Users Say Thank You to BogiesAnnex1 For This Useful Post:
AutoGear (Yesterday), joe_padavano (01-21-2020)
  #11 (permalink)  
Old 01-21-2020, 03:09 PM
Registered User
 
Join Date: Jun 2010
Location: Syracuse, NY
Posts: 4,826
Wiki Edits: 0

Thanks: 4,183
Thanked 929 Times in 758 Posts
Bogie? Just curious if you had a chance to look at the AVS2 in person? My Dad LOVES his but we didn't get to do much more with it than break the motor in. It's supposed to go to the dyno soon though.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 01-21-2020, 05:53 PM
Registered User
 
Join Date: Apr 2007
Posts: 12,732
Wiki Edits: 0

Thanks: 240
Thanked 1,249 Times in 991 Posts
I had a chance to mount a couple, tune and test drive. They were very nice out of the box on a warm street engine. One has to realize that they start like a carb not fuel injection so there always is the routine of pumping a prime shot in the manifold and releasing the choke/fast idle mechanism on a cold start. Once through that they ran very nice. On cruise using the primaries they are very linear when you stab the throttle, the engine just starts pulling no hesitation, you can't even really feel the secondaries coming on, it's just a soild pull gaining intensity as the RPMs come up, very EFI feeling.

I didn't have a chance to do mileage tests on those builds. My AVS runs 13-14 in the city, commuting on the interstate it gets 14-17 depending on traffic flow. Long free interstate crusing it get 17-19 depending on how much hill and mountain climbing is involved that with the LT4HOT cam. That's not to far off what it did with a 454 GM TBI and about 10-15 percent short of TPI in traffic and 15 to 20 percent under the TPI in long out of the city interstate cruise. Obviously it's hard to beat port injection when you just set it 75 for a few hours.

Bogie
Reply With Quote Quick reply to this message
The Following User Says Thank You to BogiesAnnex1 For This Useful Post:
AutoGear (Yesterday)
  #13 (permalink)  
Old Yesterday, 12:08 PM
boneste624's Avatar
Registered User
 
Join Date: Apr 2019
Location: Los Angeles
Posts: 54
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Gains with T.B.I.

You think I would see some gains using and tuning with the t.b.i. efi? Vs the avs2's ? Really want a Holley E.F.I. but don't have the funds atm.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old Yesterday, 02:05 PM
Registered User
 
Join Date: Jun 2010
Location: Syracuse, NY
Posts: 4,826
Wiki Edits: 0

Thanks: 4,183
Thanked 929 Times in 758 Posts
Ive never been seriously convinced that a fits-all TBI can be the answer to real fuel injection questions.
They're self tuning, easy to install and NEW...but is the ROI (return on investment) going to beat the AVS2 you already own? Doubtful. Thats my opinion. If it were me? I'd install a wideband O2 sensor and buy a fistful of plugs and a tuning kit for that carb. Leftover money? Electric exhaust cutouts obviously.
IF TBI was the answer, you'd still see the OEMs using it. Multiport Sequential is real, you will see real gains, but not on a dual plane manifold. And not at your price point.

What about a TPI manifold (tuned port not throttle body) and a used megasquirt install [or were able to flash your own PROMs and use a GM chipset.]
Jim (Nailhead) had (has?) a 327 with a TPI intake and a turbo that stomped out 500hp pretty easily.

Its possible to gut a TPI equipped car of most everything you need, and use TunerCat to tune it. Im not sure about the lower TPI manifold bolting up to your existing heads without minor modifications tho.
You'd want Speed Density I believe
Nate

Last edited by AutoGear; Yesterday at 02:14 PM.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old Yesterday, 03:04 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 53
Posts: 17,798
Wiki Edits: 0

Thanks: 274
Thanked 3,250 Times in 2,723 Posts
Quote:
Originally Posted by boneste624 View Post
You think I would see some gains using and tuning with the t.b.i. efi? Vs the avs2's ? Really want a Holley E.F.I. but don't have the funds atm.
Driveability yes, Fuel mileage yes...but more HP, NOPE. It has been proven time and again.

Little gains like 3, 4, 5 HP from fuel injection set-up but hardly enough to hang the price of the injection on....that makes it an expensive 5 Hp. The push to fuel injection is the mileage and driveabilty improvements and the ease of tuning it with a laptop instead or a screwdriver and little parts.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 05:15 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.