In order to tune a carb you need either a stretch of open, straight, level, road or a chassis dyno. With the road you need to have these tools: Screwdrivers (a jet wrench is nice) a vacuum gauge a stop watch a notepad and something to write with to keep track of each change. You will need the following parts: jets: 5 sizes + and - the existing jets in both the primary and secondary sides power valves: a selection from 2.0 to 10.5 Accelerator pump cams: all of them a set of drill bits from #60 to #80 and a pin vise (a hand tool to use with the wire drills (you can't use an electric drill) gaskets for the carb If your carb has vacuum secondaries you will need a selection of springs First set your timing and dwell properlydrive the car around to get it up to normal operating temperature. With the car warmed make your first run starting at 20 mph and accelerate to your red-line RPM with the vacuum gauge and stop watch running. (it helps to have a helper to watch the gauge and clock) Drive slowly back to the garage and let the car cool. Write down the highest and lowest vacuum readings in the run. Write down the time it took. Write down any minor defects like flat spots in the acceleration or bog on wide open throttle or whatever. Draw a line under that and do it two more times recording everything all over again. Change the primary jets up one size and test three times recording the same info each time. Change the primary jets up another size - test 3 times - record data Keep doing this until the time doesn't change or the car's performance levels off or begins to go backwards. (if it goes backwards change the jets back to where the performance was the best and begin the next step. Change the secondary jets up one size and test three times recording all the data. Keep doing this until performance levels off. Replace the power valve with the one that is a lower number than your highest full throttle vacuum at red-line RPM. Test it three times and record all the info. If the vacuum is higher than the number on the valve then go to the next number down. Keep going until the number on the valve is lower than the vacuum on the gauge. You can now tackle the accelerator pump. use each cam until there is no hesitation from standing start to first-second shift. If the cams don't completely eliminate any hesitation or bog then use the drills (one step at a time) until the hesitation goes away. Then you can tune for the fastest opening of vacuum secondaries with the different springs - choose the one that gives you the best time and not the one that feels best. One carb tuned - simple! but not quick or easy. PaulS
I have only installed 4 or 5 Holley carbs from the box. GM 454, GM502, Ford 514, Ford 351, Chry 426, and now the 302 Comet. However, every single carb required float adjustment. Every carb vastly improved performance after the floats were reset. For my money, I would start there. Charles Fla.
Paul has some great points in there. You really have to have a good feel for the car to tune the carb without a dragstrip or chassis dyno. You don't HAVE to have either one of those to get it close, but it's easier and less time consuming. Depending on what carb you have, you'll most likely have to lower the floats slightly and lean the main jets as well. 41 mpg from a '84 carbureted Mustang 5.0L/5 speed/3.73 rear. It's all in the tuning!
that's for all the pointer's especially paul you really know your stuff. i guess i will get started on the tuning thing
check this out http://www.bob2000.com/carb.htm haven't used this info yet but makes for good reading when I am still learning holleys
