So the replacement motor has no thermactor ports on the either head. The 5.0 motor in the truck has the thermactor system from the factory. My question is what will I need to do to make this a smog-legal swap. The 5.8 is from a 94 F250 and has no thermactor system and no air pump.

 

That explains it, the HD trucks use a slightly different smog system that connects to the rear of the exhaust manifolds instead of to the heads, did your motor come with the exhaust manifolds? If so you can reinstall all your air injection parts using the crossover tube from an F250 or worst case you could fake it out and just bolt the 1/2 ton crossover tube to the back of the heads.

 

Thanks for responding Conanski. Yes the engine did come with both exhaust manifolds and the Y pipe (minus the cat; it's illegal to sell used cats here in Clark County). I don't see anywhere, on either manifold, to attach an air tube to. Or is there supposed to be a long air tube from the engine bay to the catalytic converter?

I was thinking The same thing, that getting a 5.8 crossover pipe and attaching the 5.0 TAB and TAD valves to it would probably pass the visual inspection. Would that affect smog readings by not having air going into the heads though? What about the tube for the catalytic converter? I'm thinking that I may have to get a 1/2 ton 5.8-specific y pipe w/cat, in order to use the thermactor set up that is on the truck now.

Just curious what the HD smog system looks like. This 5.8 didn't have TAB/TAD soliniods installed either.

 

The air injection system only pumps air to the motor at cold start, after the engine enters closed loop and starts reading the O2 sensor it sends everything directly to the cats or back to atmosphere since pumping air upstream of the O2 would mess up the readings.

It's curious that you have a motor with absolutely no evidence at all of a smog system, maybe it came from a some special vehicle that didn't have to meet emissions like an airport runway truck or something.

 

Okay, so there should be no affect on the sniffer test since it is done on an engine that has already been running and should already be in closed loop. Would the diverter valve be affected in any way when air is diverted to the heads (with no Thermactor port)?

Re. the donor vehicle. It may be possible that it is a special, smog-exempt vehicle. Got the motor from a local salvage/recycle yard. They had another F250 with the same setup that couldn't be parted out until they received the title. I think I'll call and verify.