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Could some please describe or post pictures of the non-A/C TBI heater routing (or routings if it changed over the years)? I'm trying to put things back as original as possible after a previous owner of my car tried to turn it into a real hot rod by redoing almost everything under the hood, to the point where I don't know if the car ever ran again. I wish I could have found an unmolested car, but all the 3rd gen Camaros I looked at in my area were all done similar to this. Apparently the junior racer Chevy guys hate the 305 TBI engine. I have a 1986 Camaro assembly manual (which was listed as being for my '89) but it is of little help in this pursuit. Perhaps a shop manual might be of more help to me.
Fundamentally, the hose TO the heater core (passenger side port is IN) will come from the intake manifold, although the factory configuration might not be that simple and direct. And the hose coming FROM the heater core (driver side port is OUT) will go to the radiator, onto the nipple below the overflow tank hose, but here, too, the factory configuration might not be that simple and direct. The flow is that simple, though, so the hoses can be configured that directly, just depends how "factory" you want it to be.
Fundamentally, the hose TO the heater core (passenger side port is IN) will come from the intake manifold, although the factory configuration might not be that simple and direct. And the hose coming FROM the heater core (driver side port is OUT) will go to the radiator, onto the nipple below the overflow tank hose, but here, too, the factory configuration might not be that simple and direct. The flow is that simple, though, so the hoses can be configured that directly, just depends how "factory" you want it to be.
On the TBI manifold I was able to find at a not-so-far away salvage yard t (that I believe came off of a pick-up) there was a 3/4" nipple at the right rear of the manifold and no coolant nipples anywhere else on the manifold. There is a 3/8" hole at the front of the manifold next to the thermostat housing, but I believe that was for the coolant temp sensor.
In my '86 assembly manual it just shows the old Chevy non-A/C carb set-up where the 5/8" hose goes from the front of the intake to the heater core and the 3/4" hose goes back to a nipple on the top of the water pump. Obviously this won't work on the TBI manifold I have because there's no 1/2" nipple port at the front of my TBI manifold to screw a 5/8" nipple into.
I broke down and ordered a 3rd gen Camaro service manual last night, so maybe that will shed so more light on the subject.
I made a post the other day about whether or not to leave the rear port bock off plates on the intake manifold gaskets I got to install my TBI manifold, and I was advised to leave them on. If I end up using the right rear nipple hole to run my hose to - as was done on the truck engine the manifold came off of - do I need to leave both rear ports of the manifold open (which of course mean I have to take the intake back off)? Obviously I would want to take the plate off of the port the nipple hose goes to, but what about the other rear port (or any other port on the manifold)?
Yes, the rear manifold port to the heater core, either directly or indirectly, as you'll see in the two diagrams below.
Did the car originally come with AC? If so, then is there still a long vacuum line laying around the passenger side valve cover? If so, then that line went to a coolant divert valve.
Below is a diagram of the TPI flow, with a short hose coming off of the throttle body going to that valve first. TBI would have the hose coming from the rear port in the manifold up to that diverter valve (where the TPI throttle body hose connects), then back to the heater core as in the diagram. But that valve isn't a necessary feature, so if you don't have a vacuum line, then don't worry about it and just connect the rear port in the manifold directly to the core, as in the second diagram below.
This dated diagram below shows connecting directly from the manifold to the heater core, like you'll probably end up doing.
That diagram also shows the core's return hose going directly to the water pump instead of the radiator, as you said you've seen, which is an option for you if you don't have the parts to route it to the radiator, or simply don't want to route to the radiator. But the radiator is better because a cap on that radiator nipple isn't likely to withstand the pressure over the long term.
Yes, my car originally had A/C and a layout similar to the TPI set-up you showed, but I want to eliminate that - at least until I can get the rest of the car sorted out - to reduce the number of things I have to worry about. Personally I never liked the way GM did their A/C anyway back then: they always had that big evaporator core box (with the dryer canister bolted to the front of it) hogging all that space in the engine compartment, making it very hard to do things like change the rear spark plugs.
I like your second diagram - I think I'll do it that way. Should I take the intake manifold gasket block-off plates off both of the rear intake ports, or leave them on one or both of the ports?
I take it then that if I would want to install an inline manual water shut-off valve (to help keep heat out of the car's interior in the warmer weather) then it go on the hose going from the rear of the intake to the heater core since that is the hose feeding the heater.
12-08-2022, 05:05 PM
