1977 Lance intermittently surges

[Doug07]

On a flight today from Orlando to Nashville my lance surged several times not a lot but enough to notice. Seemed to get worse when I enriched the fuel. I switched tanks turned on electric fuel pump and changed prop settings. Nothing seem to improve it. Recently put new spark plugs in and injectors clean. Engine runs very smooth when not surging. First couple of hours ran great but the surging on the last added a little pucker factor. Any suggestions would be great. Thanks

 

[Tom]

 

[GM.]

 

[Doug07]

 

[Doug07]

 

[afmasonry]

 

[DutchNorwood]

 

[flyguydon]

 

[Doug07]

 

[sierrakilo99]