1954 pontiac rough idle

[curts54Chieftain]

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

[Mark Shaw]

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

[curts54Chieftain]

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

[rick60]

I used to own a 1950 Pontiac with a straight 8. It had a rough idle problem. It acted like a vacuum leak. I could not find any vacuum leaks externally. I removed the carb. I noticed a leak at the heat chamber for the carb. This is the area where the exhaust gasses are directed to the intake manifold to warm the carb. The exhaust gasses caused corrosion which eventually created a hole. This was an internal vacuum leak. It could be compared to a slightly open EGR valve on a modern car. I cleaned the area and applied a little JB Weld to seal the hole. The repair was successful. It lasted the full 18 years that I owned the car.(never should have sold it) Good luck with your car.