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I bought my 1973 L48 and immediately I noticed some fuel issues. Slight hestitation, bogs under WOT, floods after parking, etc. So I went to rebuild what I thought was a stock Rochester Quadrajet. Upon further inspection I could see it was a cheap after-market Quadrajet lookalike made by Jet. I'm going to ditch this carb and invest in something better. I know some of the 1973 350ci had a Holley and GM aluminum intake.I believe it was an option for the L82. I'm not trying to improve the HP by much but wouldn't mind a few more horses. The L82 was much more than a better carb and intake and I have no plans to change the cam (not to mention the 4-bolt main block). Any ideas: 1- Buy an actual Quadrajet, 2- Buy a 4150 Holley, 3- Buy a Holley and better intake?, etc. Thanks!
No factory Holley carbs or square bore intakes on Corvettes after ‘72. My best advice would be to find a correct 7043202 Quadrajet for your car, and work with Lars to get it cleaned up and working like it should. A quick search on EBay should give you a good selection of rebuildable cores.
In 73 the L-48 and L-82 used the same intake manifold, cast iron "771" spread bore intake. The 70-72 LT-1 used an aluminum intake and a Holley carb, but L-82's only came with Q-Jets. 78-80 L-82's used an aluminum intake, but it was just an aluminum version of the standard cast iron low profile intake and not a performance part.
Take Peirsonpie's advise and find a good Q-Jet core and have it rebuilt by Lars or Custom Rebuilt Carbs, you won't be sorry.
No factory Holley carbs or square bore intakes on Corvettes after ‘72. My best advice would be to find a correct 7043202 Quadrajet for your car, and work with Lars to get it cleaned up and working like it should. A quick search on EBay should give you a good selection of rebuildable cores.
This is the way
Plenty of decent, rebuildable Quadrajets still available on ebay. Before pulling the trigger, reach out to Lars for confirmation if the carb your considering is a worthy candidate for rebuild. There are a lot of them for sale but a lot of them are Frankenstein carbs made up of parts from multiple carbs. Lars can tell the difference. While your getting the carb sorted out, ask Lars for his documents on ignition timing. And FWIW, 93 octane will do absolutely nothing to address the bog or hesitation.
I second the post from ZIOGEO. You won’t be disappointed with having Lars refurbish the Quadrajet you find on eBay. Just make sure it’s the correct one for your 73 engine. Send a few pictures to Lars so he can see if it has been hacked or beat to Hell. Use Google to find the correct Quadrajet Carb Model for your 73, that way everything will fit your OEM intake manifold.
A Holley will not make your L48 run any better than a Q-Jet, and it will drink more gas.
Reach out to Lars, and his recommendations on how to spot a good used Q-Jet, and have him rebuild it.
Then it will run perfect for decades and you will never have to touch it again.
He prefers to use his email vs PMs. V8FastCars@msn.com
What you want to avoid is a QJet that has been remanufactured, they are a disaster of mis-matched parts.
If you do not care about originality, the later Q-Jets have an adjustable part throttle feature (APT) which is very handy to fine-tune your tune and MPG.
I bought my 1973 L48 and immediately I noticed some fuel issues. Slight hestitation, bogs under WOT, floods after parking, etc. So I went to rebuild what I thought was a stock Rochester Quadrajet. Upon further inspection I could see it was a cheap after-market Quadrajet lookalike made by Jet. I'm going to ditch this carb and invest in something better. I know some of the 1973 350ci had a Holley and GM aluminum intake.I believe it was an option for the L82. I'm not trying to improve the HP by much but wouldn't mind a few more horses. The L82 was much more than a better carb and intake and I have no plans to change the cam (not to mention the 4-bolt main block). Any ideas: 1- Buy an actual Quadrajet, 2- Buy a 4150 Holley, 3- Buy a Holley and better intake?, etc. Thanks!
As an option this is one of the Check out the Hollet Street demon line - best carbs I've ever installed . Saying that I have now have used both the Holley Street Demon's 625 / 750 - I can't say enough about them. 750 on the 454 Stock C3 625 on the 390 Tbird Stock Both scream to redline, throttle response is immediate and both idle perfectly. Choke operation is easy and allows me to literally drive off in less than a few minutes. Original carb needed like 10 minutes to warm up without any stumbles - this saves a ton of gas. Gas mileage is way up since the primaries are so small, this contributes greatly to driveability. Read about them and read about the Goggle Secondary Valves
Accelerator pump has three different setting adjustable from the outside, the vacuum plate spring can be adjusted from the outside as well.
Simple, Simple, Simple Demon Official Site | Holley.com
You'll need the adapter plate and i recommend the matching Air Cleaner - has a drop down base to clear the electric choke and with a 1.5 inch filter clears under the hood of my 74 Big Block.
Obviously double check your own clearances.
I bought my 1973 L48 and immediately I noticed some fuel issues. Slight hestitation, bogs under WOT, floods after parking, etc. So I went to rebuild what I thought was a stock Rochester Quadrajet. Upon further inspection I could see it was a cheap after-market Quadrajet lookalike made by Jet. I'm going to ditch this carb and invest in something better. I know some of the 1973 350ci had a Holley and GM aluminum intake.I believe it was an option for the L82. I'm not trying to improve the HP by much but wouldn't mind a few more horses. The L82 was much more than a better carb and intake and I have no plans to change the cam (not to mention the 4-bolt main block). Any ideas: 1- Buy an actual Quadrajet, 2- Buy a 4150 Holley, 3- Buy a Holley and better intake?, etc. Thanks!
Check out the Holley Street demon line - best carbs I've ever installed . Saying that I have now have used both the Holley Street Demon's 625 / 750 - I can't say enough about them. 750 on the 454 Stock C3 625 on the 390 Tbird Stock Both scream to redline, throttle response is immediate and both idle perfectly. Choke operation is easy and allows me to literally drive off in less than a few minutes. Original carb needed like 10 minutes to warm up without any stumbles - this saves a ton of gas. Gas mileage is way up since the primaries are so small, this contributes greatly to driveability. Read about them and read about the Goggle Secondary Valves
Accelerator pump has three different setting adjustable from the outside, the vacuum plate spring can be adjusted from the outside as well.
Simple, Simple, Simple Demon Official Site | Holley.com
You'll need the adapter plate and i recommend the matching Air Cleaner - has a drop down base to clear the electric choke and with a 1.5 inch filter clears under the hood of my 74 Big Block.
Obviously double check your own clearances.
Pretty sure that's a bad idea. There are lots of threads on this Forum where the most significant problem is related to the adaptor plate. It is a much better idea to match the intake to the carb.
If you want to go with a square-bore intake, perhaps the 0-90670 Holley Truck Avenger is the carb to use.
But if you are going through all that effort, just add EFI instead.
BTW, Holley agrees with the no adapter route (and I'm sure they'd be happy to sell you a Sniper EFI setup, too).
Originally Posted by Holley Website
These carburetors have been designed and calibrated as a universal carburetor for light truck
applications. It is designed for use on “square” flange intake manifolds. Carburetor adapters
are not recommended to adapt to “spread” bore intake manifolds, since adapters may have an
adverse affect on cylinder-to-cylinder distribution and ultimately, total engine performance.
However, some manifolds may be universal. Please check with Holley’s Avenger Technical
Service Department if you have any questions.
Pretty sure that's a bad idea. There are lots of threads on this Forum where the most significant problem is related to the adaptor plate. It is a much better idea to match the intake to the carb.
If you want to go with a square-bore intake, perhaps the 0-90670 Holley Truck Avenger is the carb to use.
But if you are going through all that effort, just add EFI instead.
BTW, Holley agrees with the no adapter route (and I'm sure they'd be happy to sell you a Sniper EFI setup, too).
I will,
I'll put the Demon equiped 454 "stock" against any other Carb on the market.
Sure go ahead blueprint one.....I'll do the same.
Per Holley - 750 Demon on a LS1 with produced 550 HP vs 550 EFI Same.
A small street demon is a great carb for a Hot Rod motor. And simple. But in the OPs case he would need a new square bore intake.
Since he has a stock 73 L48, not a hot rod motor, with a spreadbore intake, he would be well advised to find a decent Q-Jet and have it professionally rebuilt.
It will have equivalent performance to a demon, but deliver better mpg, and be 100% reliable, for ~100k miles.
More than likely for less cost since no new intake is required.
A well tuned QJet performs as crisp and economical as fuel injection, without the hassle of converting.
Pretty sure that's a bad idea. There are lots of threads on this Forum where the most significant problem is related to the adaptor plate. It is a much better idea to match the intake to the carb.
If you want to go with a square-bore intake, perhaps the 0-90670 Holley Truck Avenger is the carb to use.
But if you are going through all that effort, just add EFI instead.
BTW, Holley agrees with the no adapter route (and I'm sure they'd be happy to sell you a Sniper EFI setup, too).
Originally Posted by leigh1322
A small street demon is a great carb for a Hot Rod motor. And simple. But in the OPs case he would need a new square bore intake.
Since he has a stock 73 L48, not a hot rod motor, with a spreadbore intake, he would be well advised to find a decent Q-Jet and have it professionally rebuilt.
It will have equivalent performance to a demon, but deliver better mpg, and be 100% reliable, for ~100k miles.
More than likely for less cost since no new intake is required.
A well tuned QJet performs as crisp and economical as fuel injection, without the hassle of converting.
All,
I pulled the install sheets for the last 4160 I used and indeed it does have that statement recommending against it.
The Demon Install sheet does not have that statement.
I contacted Holley and am awaiting a response.
I'm with everyone about a good QJet - when they're on they're on........but, my opinion stands overly complicated and over the years....bandaid...on /bandaid....on bandaid.
I'm not building a race engine I want something that smokes tires, screams to redline, idles properly and get exceptional gas mileage.
I will,
I'll put the Demon equiped 454 "stock" against any other Carb on the market.
Sure go ahead blueprint one.....I'll do the same.
Per Holley - 750 Demon on a LS1 with produced 550 HP vs 550 EFI Same.
And make 30 mpg like the EFI solution will do? What are you getting for mileage?
Originally Posted by Dream Car C3
All,
I pulled the install sheets for the last 4160 I used and indeed it does have that statement recommending against it.
The Demon Install sheet does not have that statement.
I contacted Holley and am awaiting a response.
I'm with everyone about a good QJet - when they're on they're on........but, my opinion stands overly complicated and over the years....bandaid...on /bandaid....on bandaid.
I'm not building a race engine I want something that smokes tires, screams to redline, idles properly and get exceptional gas mileage.
I'll post Holley's official response.
The Demon carb appears to be a spread-bore design, so I'm sure Holley will be fine with you putting it on an intake that originally held a Q-Jet.
And make 30 mpg like the EFI solution will do? What are you getting for mileage?
The Demon carb appears to be a spread-bore design, so I'm sure Holley will be fine with you putting it on an intake that originally held a Q-Jet.
Thanks - confirms my positive experience with them.
FYI - I'm getting less than 13 MPG - Could be cause I'm always standing on it. With the Qjet (needed work) i don't think i was getting 10 MPG.
1974 454, Turbo 400, 2.5 inch welded dual exhaust with the shortest Cherry Bombs which are 10" - It sounds amazing.
I want to take it on a long constant speed trip - just to see what's the best MPG I could get.
<snip>
I'm with everyone about a good QJet - when they're on they're on........but, my opinion stands overly complicated and over the years....bandaid...on /bandaid....on bandaid.
I'm not building a race engine I want something that smokes tires, screams to redline, idles properly and get exceptional gas mileage.
I'll post Holley's official response.
Then you need either a well setup Q-jet or EFI. You won't get quite there with a Holley.
BTW Stingr69 gets 26.5 MPG with a 383 and a 5 speed and a Lars Q-Jet
SteveG75 gets ~20-21 mpg with a 496 and a 6 speed and port EFI.
I know of a guy with a 57 Chevy, 454,and O.D who gets 18.
Cruising of course.
It can be done.
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Carb Issues
This is the way
