i have a 88 iroc z was a 5.7 tpi now has 79 350 out of a truck when i 1st got it heat worked but not good cause it had no thermo and no temp switch for the fans got cold outside and no heat at all but that normal cause it was runnin cold so got new thermo and temp switch and its runnin around 210 still no heat so i took the valve out heater hose still none tried to flush heater core blew a hole in it and replaced it still no heat but it does have good heat goin around a 100 on the interstate preciate any help

all that is good thinking maybe not enough circulation due to worn out water pump or low system pressure guess im going to see if core gets hot also the only place anything comes out is defrost vents idk if that could be the problem

hmmmm weird one. is ur heater valve coming off ur heater core and radiator in good condition? vaccum lines may be broken or loose, thats the problem ive had.

yea it is a wierd one and im not sure what valve your talkin bout but if u mean the heater bypass valve i took it off cause my motor dosnt have ac compressor but i left the vaccume line open didnt see what it hurt

and the radiator is fairly new the only thing not new in cooling system is water pump

sounds like u might need a new heater bypass valve. also it needs a vacuum source to operate correctly.

i might be wrong but i thought all it did was keep coolant from entering the heater core thats why i took it off

replace the heater core and put back in the heater control valve. then u will have heat.
make sure the vacuum source is hooked up also.

You are correct all the valve does is prevents water from warming up your AC. Now i dont recall if removing vacuum to the valve opens or closes the valve so something to consider anyways. I would just remove it all together as they have a tendency to bind up so even though it should be open it may not be. Ive also seen TPI coolant passages in the throttle body get plugged up something to check.

its now a carb and already took off the heater control valve is the water pump or system pressure reducing circulation a possibility and the heat was getting warm tonight but not as hot as it should and then would go bak to cold

where did you route your heater hoses to? with only the heater core you should run one from top of water pump to the heater core, and 1 from the front water passage of intake to the heater core....

are u sure cause then u would have a open hole in the radiator and ive never seen anything ran like that

you cap it..it is only used as the return to radiator.. when using a bypass valve...

you could run from front of intake to heater core to radiator.....

or cylinder head to heater core to radiator .....

i prefer to use the intake manifold to heater core to water pump top because it looks cleaner.... especially if you get a hose with a formed 90 for the intake side of things...

my car is carbed so i dont have a bunch of junk in the way either

why does water pump to heater core then heater core to radiator not work(thats how i have it)

because you are trying to suck water out of the top of the radiator which often allows air into the heater core.....

trust me i went from my suggested method to this and it didnt work

i went from having an awesome cook you out heater, to a garbage sometimes its hot sometimes its not heater.. i have since switched back and now have good solid heat in the car

if you are going to use that heater hose port on the radiator, it needs to be the return from the heater core, it CANNOT be the feed.

Cause both the radiator port, and the water pump port, are returns. You'll never get heat that way. Use one or the other of those ports, and run the other hose to your intake. It doesn't matter if you tap into the coolant passage at the front or the intake or the back, but you need to tap into the intake.

alright makes since now it flows in a diff direction then i thought i was thinking water pump would push it but your right it would suck it guess i just assumed the way they were routed was right lol should have known thanks guys

Drew always has good advice!!

are you getting air out of vents, defrost , and floor seperatly when you use the controls

yea he does me heats hotter than hell now thanks man

gee im not drew but your welcome

sorry wasnt payin attention i really preciate it but thanks to everyone that contributed lol that should cover it now