quick fuel q 750

[COACH MIKE]

In response to your question concerning the Quick Fuel carb on your Keith Craft engine. I recently "tuned up" a friend of mine's Quick Fuel 780 on his 408 storker. I also have a Keith Craft 408 stroker. I checked the vacuum at idle, adjusted the idle air mixture jet screws on the primary metering block. I first closed them completely and unscrewed them 1 and 1/2 turns as a base start.
Once the engine was warm the screws were adjusted in (clockwise) 1/4 turn at a time, each side. Once the vacuum began to drop I then turned the screws out until the vacuum came up as high as possible and leveled out. Once I determined this vacuum at idle (12.5) I divided it by 2 to determing the power valve size (6.5). I then removed the front bowl and checked the jets. I found them to be too large and reduced them from the 74's they came with to 71's. The secondary's were 86 and I reduced them to 80's. The reason I made such a large scale adjustment (most carb guys will tell you to drop or add two sizes at a time) was the size of the jets in my 408 which was about the same identical engine. I had 68's in my primary's and 80's in the secondary's. I did nothing with the air bleeds. Those are probably the least of your worries. I also checked the accelerator pump. There should be
.015 between the pump arm when fully pressed and the accelerator cam arm when fully open.
I have found that engine dyno's are set up to get the most power out of the engine with no restrictions at the carb and little back pressure on the exhaust end. Depending on what type of air cleaner and exhaust set up you have, the size of the jets could have a considerable effect on performance.
Hope this helps
Da Coach