Hey all, I have a 84 z28 with a 350 swapped in, I have a good mechanical fan from a previous project, brand new 160 thermo and I believe stock rad. Every time I drive I end up boiling the coolant or overheating in some way, the rad definitely has some mineral deposits or rust or something inside but it seems to flow well, stock mechanical water pump is pushing water through pretty well but maybe it should be more? What kinda pump pressure should I be lookin for? I’ve tried running without a thermostat and flushing etc, The only thing I can think it would be is maybe the rad is clogged or the mechanical fan just isn’t enough.

any input or ideas is appreciated, thanks

 

Try a 50/50 mix of water & AF, and a new radiator cap.

 

Rad cap is new and running 50/50 already

 

My 1983 had a similar issue. In the summer I could watch gauge move from 200ish to 240 plus
in just a few minutes at a
stop light. I changed the coolant, new t-stat and even used Prestone’s coolant treatment for crusty radiators. Even tried pulling
the radiator and flushing with a garden hose. Made no difference, had to put a new Delco in to fix the problem.

Sounds like you need a new one too.

 

Do you have the lower air dam in place beneath the car... All cars will run hot without it... It pushed air up into the radiator.

You will never solve the issue without it

 

yeah it’s still in place, the AC condenser thing is out of the way too

 

Just a thought...did you mix and match parts from the original engine and the current 350? What I'm alluding to is v-belt vs serpentine, possibly reverse rotation water pump??? Then you say known good mechanical fan, was that for a v-belt set up or serpentine??? Same applies if using standard rotation fan on a serpentine and vice versa. GL

 

no sir, all stock/original setup for it. I do have another pump from a spare motor I may try

 

Does it overheat at highway speed with an abundance of airflow available?

 

I second the radar replacement onion. I had taken my original (or what came in the car when I bought it) out and cleaned the cooling fins with HVAC coil cleaner, and then used a garden hose to flush for an hour as much crap as I could out of it. The radiator "looked" clean, but still was not cooling as I liked.
I used the discount code from Rock-Auto and ordered a standard stock replacement. I was amazed at the difference in the cooling ability. Money well spent.
A word of warning, the '84 (should be like my '83) doesn't have a heater hose coming from the radiator, but the new units have a port for that (TPI cars and probably TBI), you will need to either buy a plug for it and a strong hose clamp (replace every few years) or re-route the existing heater hose setup and plug the manifold port.

 

Put a new rad in and it doesn’t overheat constantly but still runs pretty hot, 190-210, is that acceptable ya think?

 

That's pretty normal. I prefer 185°-200°, but thirdgens (and modern cars) were designed to run hot. In fact the electric fans didn't even kick on until 222°...

 

190-210 read from the factory gauge is acceptable for these cars (in stock style configuration). We all know that the factory gauge is notoriously inaccurate at best.
But glad the new radiator solved the problem. I hate tossing money at the problem, but in this case, money well spent.