I'm looking to learn to tune my carburetor myself since every place I've called in a 100 mile radius wants to charge 400 dollars or more for it. I know it's not that simple to do, but looking at videos has given me confidence that I can pull it off with some help, advice, and tips from everyone here.
To start, I have a Holley 750- List number is 80508-10 I believe, but I can't find the -10 anywhere that I look online. I don't know the jet sizes in there just yet since I'd have to take the float bowls off to figure it out. I was recently running it down in Augusta, Georgia with decent gas mileage and smooth gear transition (It's an automatic turbo 350 transmission). Gradually, through Kansas, we started noticing issues with the altitude as was expected. I knew I'd have to get it tuned for sure- I just didn't know they charged so much in Colorado for it.
Now that I'm in Colorado, it goes all the way to 4000 RPM before kicking into 2nd gear, and 3rd gear is around 3500 RPM and generally takes place a few seconds after going to 2nd. I know this has to be because of the altitude and thin air. It's running rich and the fuel smell is strong. If this information gives some good ideas on a place to start, I'm glad to provide more details.
What tools will I need? I have basic screw drivers, wrenches and sockets, of course.
I'm in the same boat as you, need to tune my Quadrajet, but I've never done it before, and haven't started my first attempt yet.
From what I've read, an air-fuel ratio sensor welded into the exhaust header, with accompanying gauge will be very helpful. Otherwise you'll never really know if you've reached the stoichiometric ratio of 14.7:1
I’ve tinkered with a number of carbs. I found the Qjet works very well with our engines. I could never get a holley configured properly. They are good carbs but they require more knowledge to configure them. After market eltelbrock carbs are common on Pontiac but you may have trouble setting up the choke. The proper OEM QJet carb might be your best less cost solution in the long run.
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Nothing wrong with a Holley Carburetors are calibrated at 70° at sea level. Decrease the jet size, one number for every 2000 ft. increase in altitude. You also may need to increase your timing a few degrees.
All you really need to change the jets on a Holley is a screwdriver. I'd go down at least 2-sizes on the primary and try it.. I'm not familiar with that model, but if it has a power valve you may have to change it too if you get a stumble when you put your foot in it.
-=>Lee<=- Due to budget constraints the "light at the end of the tunnel" has been turned off!
Holley are a breeze to tune. Your 4160 vacuum secondary carb shouldn't need much. If you plan to stay in Colorado, you need to jet it properly. Two ways to do that, either read the plugs like was done for years, or buy a sniffer and test the exhaust gasses to determine air fuel ratio. My holley run about 12 to one when I'm on it, and close to 14.7 at cruise. You could always find a chassis dyno and b have them tune it. Of course if you are passing thru Colorado, I wouldn't change anything. The f/I cars all adjust on the fly, carbs require manual adjustments. Let me help you, that 4160 carb has a aluminum tube that connects the front fuel bowl to the rear. When you disassemble it, you will need a new oring on each end of that tube or it will leak. Have them before you disassemble the carb.
