Engine stall on hard braking (demon carb)- HELP

[jhv48]

Originally Posted by Grubby

Jim,
Can you tell me the specifics on your engine? Cam, Intake, heads, compression? How much total timing do you have? I assume you lowered the rear float to the bottom line.

I played with the base plate adjustments some more tonight. Per Demon Tech I exposed a little more of the secondary transfer slots. Then, I went through the idle adjustment again and got 15 mm/Hg. I confirmed my base timing is 18 degrees and the total is at 38 degrees. No sign of detonation.

The stall is 50% better, but not gone. It sounds about like yours.

John

I've got my throttle blades adjusted so that there is no transfer slot showing on the secondary side and the proper amount on the primary side. I have 18 degrees initial timing and 38 degrees all in at 3200 RPM. Both float levels are at the lower line. I have a mild street cam (224 degrees duration with .514 lift.) 9.5 to one compression and 6 pounds of fuel pressure. A good street engine. I pull 17 pounds of vacuum at idle but it doesn't run right at that setting, so I richened up the idle by an eight of a turn to get rid of an idle circuit stumble on light accelleration.

Start there and then adjust the idle mixture screws to give you the most vacuum. Set the idle speed screw to 900 RPM and take it for a ride. Try to accellerate slowly away from a stop. If you feel a hesitation, (when transferring out of the idle circuit) adjust all four idle screws (I assume you have 4 screws) OUT about another 1/8 th of a turn. (richer). Now go do the accelleration run again. If the hesitation goes away, leave the four screws alone. Your idle is now just where it wants to be for best driveability. Several tuner articles have suggested lowering the float level for street use to the bottom line. It cured about 80% of my problem, but if I really stand on the brakes, it still acts like it wants to stall. But it doesn't actually stall.

Hope that helps somewhat.

PS, the idle eaze is primarily used when you have a radical cam that won't give you enough vacuum to set the idle properly. If you have a street engine, you should tighten the screw into the base and leave it there.