tuning carb to MSD two step

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mean318

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Good day everybody, In my quest for 12's and to improve consistency, I now own a MSD 2 step for my digital 6al. I am wondering how I should tune my Holley 750 with vacumm secondaries to run with it. I ran it last weekend and I had a lean bog coming off of the two step. I then went without the two step and 60 foot dropped back down. Any help would be greatly appreciated.
 
Could you get a vacuum guage inside the car and tune the secondaries to open with the guage
 
well, I had the MSD unhooked for a week and the car ran okay. Now I decided to hook back up to start tuning at the track this weekend and now I have a real bad miss off idle up to about 4000 rpm. I let it run bad at about 3000 rpm and shut it off and pulled the plugs and they are very rich! I run a 750 vacuum secondary Holley with 77 primary and 89 secondary jets, with the lightest spring for the secondaries. There is no bog when I stomp it rich or lean. It seams that my 2 step is set at a rpm range of 2500 to 4000 rpm.
 
77/89 are some pretty big jets for a 750 vacuum secondary holley..stock is like 72 primaries.

you still have power valve in primary?

you might want to try a stiffer spring...just remember if you are floored on the 2 step...you do not have any acelerator pump shot left to cover the fast opening of the secondaries..
 
Well I started with 75 on the primaries and I had a bad lean miss while driving with the MSD. I will try to jet down the secondaries a couple. When you say slightly stiffer spring should I go one step stiffer or two. BTW I am running a powervalve on the primary side.
 
Well I found the problems the carb secondary throttle plate shaft was worn out, I know basic stuff that I missed when putting the carb back together. The MSD was also not working right for some reason. I ended up putting my Thermoquad and the chrome box back on and for the first time ran a 12!
 
When you are on a brake at the starting line you are off the idle circuit.
Throttle is wide open.
So I tune the air fuel off the wide band sensors.
 
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