I've used the water heated plate between carb and manifold despite being told about heating the carb vs manifold.
What I did differently was to use a thermostatic vacuum switch from a 70's emission control engine to control a vac operated valve in supply line.
This screws into top of thermostat cover.
I plumbed the water off a 292 lower housing,
(a late 70's van item-has three 1/2" holes and no large bypass-there exists a matching pump)
water passes through an Olds heater shutoff valve modified to take vacuum to open-therefore it fails shut.
I plumbed heater core supply seperately;
the manifold and heater return join at a tee and go back to water pump.
This way I had heat if manifold was shut off.
I believe those vacuum switches should still be easy to find. I think they're marked for temperature they close at. A good parts guy will help. You want the one with two vacuum hose connections.
You want a water valve where the vacuum actuator linkage arm is removable so you can file a new notch and turn valve 90 deg from normal.
I believe the last 250 sixes used a vacuum operated heat riser valve; setup simlar to what I did. Probably what inspired me.
Good points: It worked!
Doesn't involve exhaust system.
Bad points: You have to wait for water to warm- so if you're cold so is manifold!
Oh yeah you should like plumbing........
BTW: Ford used those plates so you see them at flea markets, came in two and four barrel versions, don't know if they're available new.
