1975 quadrajet
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Joined: Oct 2011
Posts: 50
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From: Merritt island Florida
1975 quadrajet
Greetings
I have a 1975 C3 corvette.
It has the original L47 engine with 142,000 miles & automatic transmission.
it,s a good dependable car.
I had a rebuilt carb installed, as the original one was causing it to have bad gas mileage; 12 or 13
mpg in mixed city/country driving.
The car with the newer carb, runs just as good as the old one, however I can't get it to idle right,
the high speed idle was too high, and I need to set the low speed idle high to keep it from stalling.
It doesn't idle very smooth also.
So, I adjusted the hi speed idle much lower, but the high speed idle stays on until the car warms up
(about 10 miles) runs about 15 to 20 mph with my foot off the throttle hot or cold.
What do you recommend? Try to tune the newer one, or just put my old one back on and live with the
bad gas mileage?
By the way, I drive it like an 80 year old.
Thanx in advance
N
I have a 1975 C3 corvette.
It has the original L47 engine with 142,000 miles & automatic transmission.
it,s a good dependable car.
I had a rebuilt carb installed, as the original one was causing it to have bad gas mileage; 12 or 13
mpg in mixed city/country driving.
The car with the newer carb, runs just as good as the old one, however I can't get it to idle right,
the high speed idle was too high, and I need to set the low speed idle high to keep it from stalling.
It doesn't idle very smooth also.
So, I adjusted the hi speed idle much lower, but the high speed idle stays on until the car warms up
(about 10 miles) runs about 15 to 20 mph with my foot off the throttle hot or cold.
What do you recommend? Try to tune the newer one, or just put my old one back on and live with the
bad gas mileage?
By the way, I drive it like an 80 year old.
Thanx in advance
N
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Send your original carb to Lars and have it properly and professionally restored. That is the best thing to do.
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Joined: Oct 2011
Posts: 50
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From: Merritt island Florida
Thank you for the advice, I've heard that Lars hates the 1975 Quadrajets & I don't think he will touch it.
I will have the old one installed back & live with the poor gas mileage.
I will have the old one installed back & live with the poor gas mileage.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
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From: FL
My '75 was an original L-48 4 speed car with 3.36 years. 15 mpg stock was about the best I ever got. Swapping to true dual exhaust and headers got me up to 20 mpg. Mild cam, retune, still at 20. Tremec 5 speed finally got me to about 22 mpg.
BTW, Lars tuned my carb twice (never did the full rebuild). He is the man for Q-jets.
BTW, Lars tuned my carb twice (never did the full rebuild). He is the man for Q-jets.
Last edited by SteveG75; Feb 19, 2022 at 08:11 PM.
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Joined: Nov 2020
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From: Central WI (summer) South Texas (winter)
As mentioned above, eMail Lars before sending anything his way. He’ll provide specific instructions for shipping. Sent my original 75 to him last spring as a part of my top end rebuild. I’m confident you’ll be pleased.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
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My '75 was an original L-48 4 speed car with 3.36 years. 15 mpg stock was about the best I ever got. Swapping to true dual exhaust and headers got me up to 20 mpg. Mild cam, retune, still at 20. Tremor 5 speed finally got me to about 22 mpg.
BTE, Lars tuned my carb twice (never did the full rebuild). He is the man for Q-jets.
BTE, Lars tuned my carb twice (never did the full rebuild). He is the man for Q-jets.
I have a 1976 Corvette and may have him do mine in the future. From photos he does fine work! I was just wondering if he can tune it after the rebuild for the particular engine or does it need to be done when you receive the carb back?? Good luck with yours.
OLE442
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Joined: Jun 2000
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From: FL
Did Lars tune it remotely and ship it back to you and you just bolted it on and went with it or do you live near him and he did it in person on your Vette?
I have a 1976 Corvette and may have him do mine in the future. From photos he does fine work! I was just wondering if he can tune it after the rebuild for the particular engine or does it need to be done when you receive the carb back?? Good luck with yours.
OLE442
I have a 1976 Corvette and may have him do mine in the future. From photos he does fine work! I was just wondering if he can tune it after the rebuild for the particular engine or does it need to be done when you receive the carb back?? Good luck with yours.
OLE442
Second time, was about 5 years later. I was in RI. Engine had been rebuilt with Edelbrock heads, roller cam, etc. Lars was doing his “Tuning for Beer” tour then and I caught up with him in MA (might have been NH).
Melting Slicks
Joined: Oct 2010
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From: "ɹǝpunuʍop", Adelaide, South Australia
In 2017 sent my '72 carb and distributor from Australia to the US for Lars to work his magic on.
I also had purchased local to me a correct numbers carb to be used as a parts donor.
In his shipping details i supplied all the info about my engine, heads, cam, drivetrain etc.
Shipped them all off and was kept apprised the whole time regarding the process, emails with photos, problems etc.
Lars had to supply a few parts to make 1 good unit out of everything i supplied.
Photos were sent of it running on his test engine and final afr numbers.
I received them back a few weeks later, bolted on, primed and my engine fired straight up, final set of timing to his figures and all good.
and has been running great since then, even works on the other side of the world "uʍop ǝpᴉsdn"
I also had purchased local to me a correct numbers carb to be used as a parts donor.
In his shipping details i supplied all the info about my engine, heads, cam, drivetrain etc.
Shipped them all off and was kept apprised the whole time regarding the process, emails with photos, problems etc.
Lars had to supply a few parts to make 1 good unit out of everything i supplied.
Photos were sent of it running on his test engine and final afr numbers.
I received them back a few weeks later, bolted on, primed and my engine fired straight up, final set of timing to his figures and all good.
and has been running great since then, even works on the other side of the world "uʍop ǝpᴉsdn"
Team Owner
Joined: May 2001
Posts: 87,367
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From: Western NY
With respect to the earlier comments regarding the '81-'82 carbs, they have an electronic mixture control solenoid that works in conjunction with the oxygen sensor that's located in the exhaust system. These Q-jets have an adjustment that's required to perform with the carb installed, and the engine running. You use a special tool to adjust the stroke of the plunger that a solenoid, that's located in the fuel bowl, controls. It's accessed through an opening in the top of the airhorn casting. After you make the necessary adjustment, there's a soft plug that you tap into place, to seal up the carb.
Burning Brakes
Joined: Feb 2022
Posts: 988
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From: South Carolina
Well,at this point, I’m assuming Lars is a person,lol....now,back to the carburetor,I just bought this 81,and I do know in the late 90s, 1997 to be exact,the owner then had work done to the engine,I have receipts for parts,and labor,and from what I can tell,and not sure why,but he did replace the cam,lifters and some gaskets and replaced oil pump.also see they did some carburetor work,put a hydro jiffy kit,and had to replace the base plate twice.I have tried calling different places,and even try to find the previous owner that did this work,and found out he worked at a dealership in NJ as a salesperson,I think they were a Buick dealership.he has moved to SC,which is where I’m from and live now,although he’s about a 100 miles from me.in fact it’s a possibility I might could reach out to him on here.
Burning Brakes
Joined: Feb 2022
Posts: 988
Likes: 183
From: South Carolina
And another ? Although I will have to look underneath,to see if I even still have the converter on it,but do know at sometime not to long ago someone did replace the pipes,but I still have the original manifolds exhaust coming off the block with all the air tubes on each side,and was thinking about putting headers on it,so,the smog control will be gone,so,if I have this type computer carburetor will it even run with headers,or will it have to be retuned.