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My 78 class C has a Dodge 440 with Thermoquad. It was running great until coming back from a trip when it began to bog down under load. Normal level driving is fine, but when I accelerate uphill it bogs down and black smoke comes out the exhaust. If I back off the gas and run at less than full load it perks up and is ok.
I looked for a lose vacumn line or something obvious, but didn't see anything. Something must be affecting the choke perhaps? Any ideas?
Thanks
With black smoke I'd say to look at the choke, PVC, accel pump, float, or a bad muffler. The muffler may have lost a baffle and be causing a restriction in the flow at higher RPMs. Same with a cat. conv., sounds weird, but have had to diag. that problem B/4.
Also ck. fuel pressure at high RPM (over 2500). Pressure may be too high for carb float to handle.
Had the same problem with my 79 class A with 440 eng. I think heat build up in the engine compartment may contribute to the problem.
I mounted a 12 volt blower below the front grille and routed it through a metal dryer flex duct and located the end where it blew directly on the carb. bowl. That actually solved the problem...don't know if it would work in your instance.
Good luck with your project, let us know what the fix turns out to be.
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