Hi,
I have cooling problems with my -85z.It has 355(880 vortec block).I use waterpump from my previous 305 (standard rotation pump).Thermostat is brand new 180F deg high flow summit unit.It has drilled four 11/64" holes for by pass coolant circuit.
Radiator is Modine 1R951 replacement unit.
Symptom is:car overheats occasionally,it raises temp from ~180F to 260F,but if I give to engine more throttle,temp lowers.It makes this at highway and also when standing still at idle.
When temp raises and I give it throttle,upper radiator hose collapses.Car has lower radiator dam,ignition advance at idle is 25 degrees and a/f ratio is at idle ~15.5-16.5 and at cruise ~14.7-15.5
First I think that it was bad thermostat,and I replaced it to new one,but no difference.Do I need betterflowing waterpump/thermostat or what?

-Jari-

 

are you running a serp belt system?

 

That's basically the engine I am putting in my car in the next couple of weeks...I'm interested to see how this turns out as I will also be running my V-belts from my 305 along with the stock waterpump.

 

No,original v-belt system.I replaced waterpump yesterday to Weiand action plus pump(made in china...).Test today how it works.

Is that little hole below bigger hole at waterpump mountingoint at block to by-pass cooling circuit?

-Jari-

 

Update:Old pump was defective.No more overheating with new pump.