Emissions-temp control valves

M

meisterj

Member
Hello,
recently purchased a '74 Scout II with 345, 727 auto trans, 4x4, originally from CA or hi. The diverter valve on the air pump is bad, and the general consensus is to junk the emissions stuff (not needed to pass a smog test in my state, nc). I am not an engine guy. I gather that involves removing the pump, injection manifolds, egr valve. I see a plate for blocking the egr valve port. What about the low temp(2) and high temp control valve(1)? Do they get removed or not? If not, do I just plug the vacuum ports or leave the vacuum lines functional? If so, how do you plug the ports? I guess I really don't know what these valves do, so don't know how to handle them. Thanks!
 
No need to remove the temp sensitive vacuum switches. Doing so would create major coolant leaks unless you then plugged the vacant holes with a pipe plug. As long as no active vacuum signal is plumbed to either switch, all switch ports can be left unplugged.
 
A 3/8" socket head pipe plug will fill those holes nice and clean. Make sure to remove the air tubes in the exhaust ports and use the proper plugs so the exhaust ports don't chirp.
 
Thanks for the info! I've read about the air injection tubes, the chirping, and the options for plugging the ports. I assume the tubes are rusted in place. Can they be removed easily through the injection port after removing the manifold, or does the engine need to be torn apart?
 
To start with I'd try to use an easy out, twisted not straight kind, to try to pull them out the top of the port. If that does not work, the exhaust manifold can be removed and they can be pushed up and out.
 
Regarding the chirp: I envision it is created by exhaust gas flowing across an orifice, like blowing across a soda bottle opening. However, based on a picture of the injection tube (that I May be remembering incorrectly), it projected into the exhaust port such that the gases flowed along the tube and past its end, not across its end. If this is the case, leaving the tube in May not create the chirp, whereas taking it out would create the chirp as the gases flow across the orifice for the tube. Of course, this is in my head. Any real life experience as to whether the chirp occurs with injection tubes in versus removed?
 
You understand the issue. The oem plugs fill the entire hole in the head. Something like these May work. https://www.mcmaster.com/#92505a654/=15sdriv
92505a654p1-b01-digitall@1x_636117945188079567.png
 
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