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Discussion Starter · #1 ·
Hi Friends


I have been concerned with poor mileage as I work on my beast. I have tested the compression of all cylinders and I am at 150 psi all cylinders with only a 5 Psi change on the oil squirt. A bit of blow by noise from the dip stick and leak down test showed some valve leak.

Im trying to turn my thoughts to analyzing how much gas is burning in the engine. I could mount o2 sensor with a lot of work. But would not a smog test shop be able to tell me if Im running rich or lean .

No blue smoke
no oil consumption
two different carburetors give the same mpg results
all ignition components have been replaced and the dizzy re curved.
timing set at 15 TDC
 

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1969 Mach 1 351 Black Jade
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Install an Air/fuel mixture gauge, adding an O2 plug on the headers is a 5 minute job at an exhaust shop or easy to do at home with a welder.
 

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An 02 sensor would help but unless you know how to tune your carb, you'll be chasing your tail. Carbs are not that difficult to understand, but you need to understand where to look if your A/F reading is 10:1 at idle or 15:1 at wide open throttle. Spend $25-30 on a good carb tuning book like David Vizard's holley tuning. It'll be money well spent. Then install the 02.
 

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Discussion Starter · #6 ·
With those, it usually comes down to cleaning crud out of the passages, or adjusting float levels. Maybe setting idle screws - but that's not too hard.
Yeah, It is rebuilt. so, new parts and very clean. I adjusted the float only t flood the engine. Then set it back to previous position. Only to achieve the same poor performance. I am gong to try and jet down. see if that helps.
 

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Yeah, It is rebuilt. so, new parts and very clean. I adjusted the float only t flood the engine. Then set it back to previous position. Only to achieve the same poor performance. I am gong to try and jet down. see if that helps.
There's a lot to learn about Autolite carbs. I recommend you read a bunch and talk to experts here on the board before you ever touch a jet. Most of the time, 'changes' to these carbs are not an improvement, and the original "carb problem" turns out to be a vacuum leak or timing issue instead.
 
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