[SS66chevelle]

Hey F-Bird I know this post is old but just wanted to say THANK YOU for this information. I just set the timing on my zz502 (has the smallest thumper installed) and I thought I was seeing things when the initial timing was 25 degrees.. I've never had a cam that required much more than 8-10 initial so I was really spinning my wheels.. Even broke down and called Dad for his advice knowing full well he is a "factory original" type of guy haha..

I guess I will shamefully admit I didnt even know you *could* set initial timing that high until now...

Originally Posted by F-BIRD'88

The biggest mutha thumper cam requires a lot lot lot of initial spark timing at idle.
Lock out the distributor mechanical advance and set the idle timing at 34-36deg BTDC.
Install the lightest/lowest tension edelbrock metering rod/power piston step up springs.
Be sure the PCV system is hooked up to the base of the carb and is functional.
the opposite valve cover needs a breather.
Edelbrock carbs do not idle off the secondaries like a holley does. They will be closed at idle.

Once you've modified the distributor and replaced the power piston step up springs and reset the carb idle mixture and idle speed adjustment the idle will be much cleaner. The throttle response will be much better.
A 3500stall torque converter is required. (10" th350 converter) (9" th700r4)

There is no proper carb adapter for the square flanged performer carb on a factory Qjet manifold.
Change the intake manifold. A edelbrock performer RPM is what you need.
Way to much fuel distribution upset with any adapter on a Qjet manifold.
Stop fooling yourself.

If when the motor is hot, the motor is hard to start with the timing locked out, install a SPST switch on the distributor (HEI) or external spark amplifier box power switch on wire to kill the spark during cranking.
Kick it over with the spark switch off, then throw the switch and it will fire right up. Any 10A or more rated automotive grade SPST switch will work.
Mount it on/under the dash where you won't kick or knock it while driving.

Which cam do you have and what distributor? What model # carb?
Get the proper intake manifold.