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Rebuilt the carb and had it running last night, it sounds like it's missing slightly on a couple cylinders and the thermal camera shows that 5 and 6 aren't pulling their weight. I need to do a compression test, as it could be a head gasket leaking between those two cylinders. Is there any other common things to look for? would a vacuum leak between the intake and block be able to affect just two cylinders?

isaac_alaska wrote:would a vacuum leak between the intake and block be able to affect just two cylinders?

Possible but not likely to happen suddenly, spray some WD40 around the manifold/ gasket interface with the engine idling and see if the RPMs increase which would indicate a likely leak there.
I would first do a compression test just to eliminate the blown head gasket possibility.

Each runner of the intake feeds two cylinders, so a bad leak could affect a pair. A head gasket is more likely.

I had a similar situation with one of mine, which had not been run for many years. It was (as I am sure many would guess) sticking valves! Intakes.
Compression tests are good, followed by leak down test to determine location of compression loss, if need be.
Good luck with that, and let us know what you find.

also make sure vacuum hose for wipers is hooked up. when not it really affects 5 and 6 badly because the port is on that runner

i do need to cap that off better, since right now it just runs to the vacuum pump and there's nothing connected. i have it capped/plugged at the inlet to the vacuum pump but there's a chance it's not a perfect seal