Slant six with modifications runs horrible. What else can i do?

[BH75dartdracy]

Blew My old slant six in my 75 dodge dart swinger a few years ago. Replaced engine with a freshly rebuilt one, rebuild trans, added a pair of offenhouser headers, exhaust, 2bbl manifold, 2bbl new 250cfm holley carb, msd ignition,etc. Idles rough and stalls frequently. Kinda slow right off the bat. Im looking to get more power out of it but keep it as my daily driver. Was put on the dyno last year with the bad trans a too big of a carb (500cfm) and had 201 ft lbs or tourque and 98 hp. What can i do to get her running well? Any advice is welcome. Thanks

 

[powerwagonpaul]

are we to assume you have checked all the basics? valve lash? timing? no vac leaks and such?

 

[Darter6]

Start from the begining and go thru the tuneup.Just check everything if the parts are new. Include a proper valve adjustment and check for vacuum leaks.As far as the MSD make sure to use the proper plug wires and up graded coil. I had problems with missing and ruff idle with the stock mopar electronic wires and coil when I installed the MSD 6A.
Most slanters are using NGK box stock# 3459 spark plugs. The # on the plug is different than the box # and I can't recall. If all checks out then try different timing settings.This is just a start as much more can be involved.
This is just for reference your results may vary.

 

[RustyRatRod]

Stalling and rough idle sounds like a vacuum leak. You put a vacuum gauge on it? As stated, check all the vital signs for a baseline.

 

[slantsixdan]

What kind of cam is in this built-up motor…and how is it phased?