on the freeway it runs real good, but as soon as i exit off the freeway or dive in stop/go traffic, she overheats.
`my airdam is fine
`the fan switch is new (between the head and block)
`the coolant temp switch is new (by the throttle body)
`the fan relay is new (by the brake reservoir)
`the fan works, we jumped it from the battery and it spun up
`brand new water pump, flowing the right way
`under dash fuse is good too

here is something i found out though, the current cooling setup if from my 305 tbi. so therefore it has the single fan setup.
I now have a 350 tpi. and i found out that they had twin fan setups. after searching and searching i found out that the main switch powers one fan and the other fan switch turns on the other one. or something similar to that.

So my thing is, some wiring must have gotten messed up when i re pinned everything after the swap? or do i need a dual fan setup for it to work?
the PROM chip inside the ECM is for a tpi. not a tbi.
so, im wondering what else can i do or whats the next step. trust me i have been searching and still am. Im just stumped at this point.

I tried to elaborate as much as i could so someone can possibly help me on this. oh and it is getting hot. to the point where it boils in the overflow. and it will start sputtering under acceleration when it gets HOT if im driving. (usually trying to limp home)

 

in the twin fan setup one fan was run by the temp switch and the secondary fan was run by the ecm. does your fan actually turn on when the car gets hot?

 

nope. i sat there for minutes upon minutes and it overheated and the fan didnt even move. water boiled up too.

 

ok, i started it up again, and waited. the fan DID turn on. it turns on at about 230 (but i already know not to rely on the gauge)
so, its working, it cools...

however, i took it for a spin around the block and regular driving (stop signs) for about 15 minutes and it started to bog down like it usually does.
when i pulled into the driveway i could hear it burbling up (the reservoir) which means its overheating.
so I dunno...might need myself a new rad? how can you tell if the rad needs to be replaced? the fins look OK from the front. when i look inside however i can see a LOT of corrosion and buildup. so idk if thats the real problem at the moment.
like i said, fan now works. comes on 'late' according to the gauge but it is working.
and like i stated above, after driving on the highway for about 30 min doing fine, when i hit the streets, it overheats and bogs down.

rad cap is brand new too btw.

 

The 'main switch' would be the ECM controlling the primary fan relay.

TBI motors had no ECM fan control so, you would have had to added wiring to control the (a) fan via ECM.

Stock fan switch temperature is 238°F

Autozone sw505 is a slightly more reasonable, 215°F fan switch.

It's never really good to have corrosion/dirt in your radiator.

 

I'd skip the factory fan switch/ECM control of the fan all together and just install a seperate fan controller - they probe the radiator (no leaking coolant when changing switches), they don't use factory wiring (come with wires and instructions), most are adjustable (set it where you like), and well worth every penny! I run a Flex-a-lite controler, pricey at $100, but 4 years later my car never sees over 210 even just idling for 20+ minutes on a 98 degree day in the sun.

 

Yeah agreed, and also change to a dual fan. OP's climate in Cali I gather would be much the same as here in Sydney, ie HOTTT in summer. After making sure all of the cooling system was clean and serviceable, adding the dual fans is what finally got my temps under control.

I built myself a fan controller with adjustable switch points. Now it sits at typically 180 deg, max about 200 in traffic on a 44 deg c day (110 deg f). No more boiling.

 

thanks for all the info guys. I was just totally surprised that all throughout winter and even in the fall i would DD her.
now that its summer, i mean wow.
at first i thought that i had a blown head gasket since in searches it seemed that I had the same symptoms. ie bubbling overflow tank, hi temps.

its just weird that you can even enjoy a car like this during the summer without making mods to the cooling system? She gets so hot that she bogs down when i give some acclelration and putters forward.

oh yea, Im not in Cali, Im in Florida. hott as hell and humid right now!

and I just wanna ask you guys, were you experiencing the SAME things im going through now? or did yall just do these mods to get better cooling flow? thanks again everyone

 

thats what im thinking about. my neighbor was telling me the same thing about a camaro he used to own. its just soo freaking HOTT in florida during the summer. when its cool or winter out my car kicks ***. but not now. well, until it gets hott in the city driving.
where can i find a set up like you stated? part number or something? in the mean time im going to search some stuff on summit.

oh, i also bought a 180 T stat yesterday. going to install it tomorrow morning and see how that responds to the temps. wanted to go straight to 160 but i heard it could cause problems. so going with 180 for now.

just wanted to make a reply. I see others are having similar problems and open ended threads will never help anyone out.

 

tstats that are 2 low tend to not let the engine reach operating temps, which causes faster wear on some parts...180 is about the lowest you wanna go in a street vehicle.

 

ok so i put the new t stat in (180*) and i was driving it around the neighborhood. stopping and turning, etc. going pretty slow. I drove for about 20 minutes in the heat and then it happened again. the bogging down and overheating. oddly this time though it didnt go into the red (temp gauge) like it usually does. but my coolant reservoir was filled almost to the top and bubbling bad. i think i coulda boiled eggs in it.

so i think the only thing left to do is replace the lower rad hose and the top rad hose. if that doenst work im putting it in my garage and replacing the head and manifold gaskets. thats about the last resort...

 

i would start with a flush to clear out all the corrosion. easiest way to do that is open up the drain plug, pop off the upper rad hose on the rad end, remove the tstat, take the rad cap off, stick a hose in there on full blast, and start the car and let it run for a few minutes. its gonna pour water everywhere but itll clean out the system pretty good. just be careful, the water might get a little warm...