Vintage Mustang Forums banner

Is there a way to calculate your fuel ratio

414 Views 3 Replies 3 Participants Last post by  mstngjoe
Does anyone know if there is a way to caculate your fuel/air mixture from your carb cfm and jet size? Is that even possible?
1 - 4 of 4 Posts
not really....tolerances in every part of the carb, from jets to bleeds to the carb castings will prevent this...

An electronic a/f ratio monitor can be bought for 75 bucks and the hardest part of the job is getting a threaded fitting welded to your exhaust.
The more accurate way is to install an air/fuel ratio gauge. They range from around $75 to over $300. The old fashion what is to tune your carb Air/Fuel ratio at idle to shoot for max vacuum on the vacuum gauge and to read your spark plugs under load. One of the neat things about a carb is that they have a wide tolerance. As long as you get the idle circuit correct and the CFM rating is close to what you need, it will pull as much fuel as it needs via the ventures when under load. Hope this helps.
Here is a graph that allows you convert you CO readings to A/F ratio. The emissions stations here in Oregon will run older cars that don't require emissions tests for free. I used to take mine in and get the readings at idle and 2500 rpm and checked against the graph to see where I was tuning wise.
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.