Broken Heat Riser Tube Repair

[tucsonjwt]

I dont know the proper terms, but it seems like there is a metal tube running from the intake manifold (TVS?) to what looks like an emissions style heat riser at the end of the exhaust manifold on the passenger side.

The connection to the heat riser is broken - it looks like a fire resistant fabric sleeve. What is the repair for this broken part? I am assuming that an OEM part is no longer available, and I don't know where to find a piece of fire resistant sleeving. Also, is there supposed to be some sort of special connector to connect the metal tube to the heat riser.

My truck is an 83 C20 454 with SM465 manual transmission. It does not have a catalytic converter (not required for 8600 GVWR trucks until 1987) but it does have all of the other smog stuff - lots of vacuum lines, tubes to the exhaust manifolds, smog pump, etc. I do have to go through emissions every year, so I have to have an emissions compliant vehicle.

Thanks.

[tucsonjwt]

I am reading elsewhere that the exhaust manifold (heat riser) is part of the Early Fuel Evaporation system (EFE), designed to run the engine lean soon after start up. I have converted to a manual choke, so I take care of that task manually. Still, I need to be emissions compliant. I am reluctant to remove what is left of the heat resistant wrap because I likely won't be able to replace it, and I doubt that I will be able to replace the heat riser either.

[tucsonjwt]

P/N GM 5234298 is listed for an 1985-86 C20 and appears to be what I have. It looks like a standard vacuum hose bulge on the end of the nipple, but I am concerned that if I wiggle it around with that heat wrap it might fall off. The couple of replacements listed online (if they are true listings) have the part at $140 -$400. If I could find some oversize sleeving to gently clamp over the existing sleeving I might give it a shot, but so far, no luck on that option.

[blakeduren]

I have an 83 C20 Suburban 454 that had that same setup.
Good news for you is that the sensor on the engine controls whether or not that “pot” gets vacuum. If your engine is warm, that pot is not getting vac and has that exhaust valve wide open(it’s default position).
The metal vacuum tube slides into that vacuum pot. It only needs one inch of rubber vacuum hose to seal the connection. Wrap the rubber in some generic heat tape to keep it from melting if so inclined. I don’t think mine had any.
I believe this would pass visual inspection.
Let us know how it pans out!