So I’ve ran through everything normal with idle misfires and came up with nothing. I checked manifold vacuum and I got 12in of vacuum. What is the normal vacuum at idle?? Is it like most engine 18-22??
I’ve checked firing order and it’s all correct. Check timing, and it’s dead on. Check manifold vacuum and was at 12 at idle. Which seems low. I haven’t check compression yet. I’m gonna go over the valves this weekend. Just so weird how it’s pulls hard, can get to 6k every gear without skipping a beat. Just at idle it’s isles low and feels like a misfire. No cel light or stored codes.
It is possible that you have a leaking head gasket. Is there a difference when the engine is warm vs cold? Is there a difference at idle vs driving speeds?
You can test the head gasket by topping off the radiator [to the brim] with water and then removing all but one of the spark plugs (I like to go left to right; leaving the far left plug in). Leave the rad cap off. Pull the fuses for the fuel pump and the distributor (it maybe something else as I’m tired as I write this) before you start. If the water from the radiator fountains up for any of the cylinders tested, you’ve got a bad head gasket. Note, the water pump will move water out of the rad, but not much.