Only running on 4 cylinders? I think?

[jglimpse]

Ok so I have this 66 suburban with a V8. no idea what size. Sorry. So I got it running but it only seems to be running on 4 cyl, it is the even side the passenger side header gets hot when its running. I have checked the ignition every thing seems fine and all 8 cylinders are getting spark but after running say 5 min the manifold is still cold to the touch. it wont idle and when you try and rev it it is very slow to rev. I am planning to check the firing order tomorrow and other than that I have no idea what to do any help would be much appreciated. I will be more than happy to get anymore info if there is something you guys need Thanks alot

[64Magoo]

Seems as though someone stole half your internals

[LILRED66]

Pull compression on all eight and see what you have. Also, make sure the plug wires are installed and matched correctly at the cylinders & distributor.

[markeb01]

I'm with Tony on needing a compression check to get a baseline. Assuming you already checked for a broken distributor cap, it could be a bad head gasket between cylinders, although when they fail in that area they usually only fail between two cylinders, not four.

Was this truck ever running during your ownership? It would help to know the engine history - if and how it was running when last driven. If a failed engine was why it got parked, it may have big problems.