In reading thru the old posts I found this seems to be a common problem on Roush 427R motors. Mine was built in 07 which is a suspect year. The problem is rolling onto the throttle results in a spitting, coughing, etc. The lower the RPM and the higher the gear the worse the problem which makes crusing in 5th a real pain. It clears up quickly in all cases and when it does...... I read about the red, blue, Green dots. Can someone provide some history and where to find these dots on the carb.
Cobra Make, Engine: SPF 2932 with 438 Lykins Motorsports engine. Previous owner of FFR 5452.
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You have a four corner adjustable idle circuit on your Holley 750. Try richening up the idle circuit about 1/8 of a turn on each screw (out).
My Demon (Holley Clone) exhibits the same stumble when rolling on the throttle slowly when the idle circuit is a little too lean.
Hope that is it. If not, check the float levels on both bowls. Should be at the bottom of the screw on plug's threads. Next will be the squirters. Both should begin to squirt as soon as the throttle begins movement.
the dot is on the front of the caliper, take off your air cleaner and it should be there, i think the most recent edition is green. I also have the 427sr and have to admit it is the best running carburator engine i have ever had. I can run around all day long at 1500 rpms with no issues.
Cobra Make, Engine: SPF1715, Roush Built 434 ci Stroker, Dart Block, Ported AFR 205 Heads... 561 hp / 547 tq, Former Roush Show Car, Completed and Prepped By Olthoff Racing.
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My motor used to do the same thing until I changed to a 4150 HP series Holley with billet metering blocks, and had a good carb guy dial it in and it does not stumble at all now.
Throttle Hesitation
Hybrid Mode
