warming car up

Just to let you know that your main jet size doesn’t come to play when at idle and oil contamination is caused by rich barrel valve adjustment. The barrel valve uses the slot in the spool with the excess fuel going back through the idle return check valve. If you are contaminating oil with alcohol then you need to change your barrel valve leak down percent by a couple smaller. You can keep leaning it out as long as you don’t get a hesitation if you quickly rev the motor off of idle. If it blubbers off of idle it is too rich, if it hesitates it is too lean. It should be nice and crisp and aggressive sounding

 

I agree in what you are saying about using the fuel shutoff but it is obvious his BV is out of adjustment so I would adjust it correctly first then use the fuel shutoff trick

 

In my tuning experience, the barrel valve adjustment should be to hit a target cylinder head temp at staging (and part throttle stage flow if you have clutch car or part throttle converter leave). The trend over the years is to have a cool head at stage, so the idle flow is going to be on the rich side if you are doing that.

As mentioned, I have trimmed the fuel shutoff during the warm up to accomplish this. Usually trim it just enough to bring it off idle.

Every roots car I have tuned, I've been able to get a clean idle that doesn't get the heads too hot, so I rarely have to trim the fuel shutoff to warm it up.

I run a pretty rich idle mixture with a screw car, so almost all of them I've had to trim back. The thing you want to be careful with a screw is to not trim it too far. If you get it too lean at idle, you will heat the blower up and potentially cause damage. I always reach under the back of the blower and feel the case where the rear plate bolts to the case to see if there are any signs of heat. There should be none. If so, give it some more fuel at idle until it quits feeling warm. If you have a dash and flow meter, you can trim it to a target gpm.

During normal temps, I idle for 90 seconds with the fuel shutoff trimmed. Cooler temps will take 120 seconds. I make sure that I can feel heat in the oil line going to the filter before I turn the fuel back full open.

I never touch the throttle with the fuel trimmed. When it's back open, with a clutch car, that's when we bring it to stage rpm.

I usually bring the motor up myself as well and do a good throttle gap. Why? Because it sounds cool. That said, I'm not a fan of gapping the throttle off idle.