jay27 said

Im not sure how to diagnose sputters , however I would look at what has changed since the dyno.
Fuel , is the fuel fresh , does the carb have a stuck needle and seat
Ignition , what has changed , plugs, gap , coil , MSD box
You can move the distributor 180 degrees and it does not backfire? confused by that.
You have a good response above and if possible post a video, good luck.

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67Dart273 said

Basics are fuel, compression, spark

Compression: Have you checked? Cam timing, dry cylinders with no break in, fuel washed off cylinder walls, incorrect valve adjustment, or wrong push rod length. Run a compression/ leak down test

Fuel. Make sure it is actually gasoline and FRESH. Obtain some known fresh gas in a squirt bottle to hand prime carb throats

Spark. Must be adequate spark and at the right TIME. You can check timing with a light "on the starter." With MSD you should have MASSIVE spark. CHECK SPARK NOT while jumpering starter relay, but rather WHILE USING THE KEY to crank the engine. That is important

Google and be aware of "rotor phasing."

Are the plugs fouled with fuel?

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jay27 said

Im not sure how to diagnose sputters , however I would look at what has changed since the dyno.
Fuel , is the fuel fresh , does the carb have a stuck needle and seat
Ignition , what has changed , plugs, gap , coil , MSD box
You can move the distributor 180 degrees and it does not backfire? confused by that.
You have a good response above and if possible post a video, good luck.

Click to expand...