Adjusting a 1971 350/270HP stock Quadrajet
Thread Starter
Obsessed
Joined: Apr 2019
Posts: 627
Likes: 394
From: Valencia, Spain
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2019 C3 of Year Finalist (stock)
Adjusting a 1971 350/270HP stock Quadrajet
Hi, still can’t drive my 71 yet but I do visit often and let it run for a while. I notice the high idle seems to take a long time to drop down. High idle is around 1200 rpms and drops to around 7 or 800... if my memory serves me well. Anyway it seems high and I can let it idle and watch the gas gage go down 😳.
The octane level here in Spain is 98 for premium and 95 for regular... I’ve been using 98. Do I need to make some adjustments?
Note: the engine was rebuilt to stock specks around 10,000 miles ago except for a L 82 cam was used in place of the L48...
Melting Slicks
Joined: Apr 2010
Posts: 2,794
Likes: 1,195
From: Canberra Australia
2025 C3 of the Year Finalist - Modified
Hi Dave
it will only drop off high idle once it has got to temperature and it then takes a movement of the gas pedal to allow the cam to disengage.
While driving this this just happens but while sitting still you would need to specifically blip the gas pedal to do it.
sound Fine to me.
it will only drop off high idle once it has got to temperature and it then takes a movement of the gas pedal to allow the cam to disengage.
While driving this this just happens but while sitting still you would need to specifically blip the gas pedal to do it.
sound Fine to me.
Thread Starter
Obsessed
Joined: Apr 2019
Posts: 627
Likes: 394
From: Valencia, Spain
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2019 C3 of Year Finalist (stock)
Hi Dave
it will only drop off high idle once it has got to temperature and it then takes a movement of the gas pedal to allow the cam to disengage.
While driving this this just happens but while sitting still you would need to specifically blip the gas pedal to do it.
sound Fine to me.
it will only drop off high idle once it has got to temperature and it then takes a movement of the gas pedal to allow the cam to disengage.
While driving this this just happens but while sitting still you would need to specifically blip the gas pedal to do it.
sound Fine to me.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
There is no carb tuning required (or possible) for higher octane fuel. Your '71 is a low-compression engine - why do you want to use high octane fuel? It will gain you nothing. Use the lowest, cheapest octane you can find - your '71 does not need premium fuel.
If you're concerned about mileage, work on your timing curve. Timing has a much greater effect on fuel economy than the carb. If the carb is simply set up to its stock specs, it will run as lean and economically as you would want it.
Your carb's idle speed numbers are right where they should be. You don't have a problem. Drive it and don't worry about it.
Lars
If you're concerned about mileage, work on your timing curve. Timing has a much greater effect on fuel economy than the carb. If the carb is simply set up to its stock specs, it will run as lean and economically as you would want it.
Your carb's idle speed numbers are right where they should be. You don't have a problem. Drive it and don't worry about it.
Lars
