After my 1954 Pontiac chieftain with the 268 cubic inch straight 8 warms up I have a rough idle with and without car in gear. What could this be any suggestions? Also you can check out my Pontiac at www.54chieftain8.webs.com

Assuming you cheked all the standard stuff, spark plugs, wires, points, valves adjustment, etc.... Try testing your valves and rings for leakage.

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index1.html

yes i hae checked all the standard items new plugs,wires,cap,rotor,points,condensor,and coil. so will check this out thanks.by the way when im going down the road at highway speed after warm runs great till slow down. any other info then that may be of use? thanks curt