Hey everyone new guy here. Looking for a little help. 1966 225 in a 67 coronet. Engine looks like it’s been rebuild but don’t know any history about it. I bought the car about a week ago and it just hasn’t run right. Getting a misfire that really isn’t noticeable at idle but when I start driving I can hear it missing while cruising. So after reading some threads on here I changed the rotar and cap, the wires, I rebuilt the Carter afb, replaces the plugs with the recommended NGK, and added a fuel pressure gauge as I thought maybe it was being flooded from too much fuel pressure. Well that didn’t help much. It was better but still missed while at cruising speed. So I decided to pull wires while running to try and find which cylinder was missing and determined it was number four. I pulled the plug and bam looks brand new. Compared with all the others and they were nice and tan. So now I was going to check spark on that plug alone but I wanted to know wouldn’t that plug still be wet and dirty from running for a week?( just from the fuel and carbon being compressed against it)

Also I have done a compression test and all were at about 150.
Any advice would be appreciated.

Possible vacuum.leak on the #4 at the intake gasket. Spray some carb cleaner around the gssket with it running and see if it changes snything.

Also check at the joint where the carb mounting plate joins the intake. I have had that gasket leak more than once.

_________________
Official Cookie and Mater Tormentor.

If you're not getting spark on #4, try swapping wires with #3. Not likely to have a bad wire out of the box, but it's easy to test. Might also check to make sure you're getting a solid connection on both ends of the wire. Finally, you might just have a cap/rotor set that's so far from true that they're not making a good connection underneath. Aftermarket parts are not always well made. Maybe pull the cap and check for arcing or scoring?

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing