Hey guys..I got the 300+ HP SBC running great but cant keep er cool with the CU511 Rad...the Thermostat opens ok...and when I start er up when warm the temp drops good so I am thinking the water pump is doing its job too...the 16" electric puller fan cant seem to keep up.It does take 5-10 mins for it to get too warm..is it possible that its too much engine for the CU511? maybe I need 3 or 4 passes? any opinions are very welcome..Thank you

 

pull the thermostat out for a test.. I spent months chasing an overheat that turned out to be a too restrictive thermostat.

Sam

 

How hot are we talking about? If it's a new engine, it will be a little tight and may run warmer than normal until you get some miles on it. The timing may be a little off also. The CU511 is a three row radiator and should be plenty to cool your 350. It cools my 355 with a mechanical clutch fan even without a shroud...

 

Sam--What do you mean too restrictive? You mean too high of a temp?

 

Thermostats restrict the flow of coolant to ensure it stays in the radiator long enough to cool it. Depending on the radiator and/or engine combination a thermostat may restrict the flow too much...

 

no.. wouldn't let enough water flow thru. it was one of the stats that was a 'can' with the 3 holes in the bottom instead of the spring exposed..

the radiator guy bought an el cheapo stat and cut the guts out, leaving only the hat, and the overheat problem went away.. (course it cooled off too much while driving, so I installed a real 195 degree cheapo stat later)

see the pics here https://www.ford-trucks.com/forums/8...ml#post7928579

the right/bottom is the can (problem) type, the center/middle is the one I use now, and the one we cut the guts out of.

so, the water flowed too slow, and collected more engine heat, but couldn't dissipate the heat, so came back a few degrees hotter, and picked up more heat, and... repeat.. slowly climbing til pop!..

Sam

 

Thanx guys... I looked on the spectra premium site and it said 2 passes or rows is that a 2 core? I wasnt aware that it was a three core as its way thin...anyways ..if it works on your 355 it should easily cool mine...I changed the thermostat and saw a difference it stayed at 185 for 10 mins with the electric fan on...I am pretty sure my thermo switch for the fan is not working...earlier it spiked over 210 and I could barely cool it down..I am hoping it was the T stat

 

also, Sam do you have a CU511 as well?

 

no.. but I don't think the rad is the problem.

sam

 

I dont think so either...its the operator!!!

 

nah..

all I was suggesting is to test and see what the behavior is. I spent months changing everything else, cause it COULDN'T be the problem, as it opened and closed at the defined temp just fine, and was new...

good part, bad application..

if you want, buy a cheap thermostat and cut out the temp sensing part, leaving just the hat, and put that in instead. that will give you max flow.

as your symptoms sound exactly like mine, slowly escalating temps.. I'm betting this could be the same problem.. particularly on a newly rebuilt engine.

sam

 

I agree Sam, I just had a conversation with a buddy of mine...he recommended the milodon 180 degree high flow unit at summit Worth a try

 

Is this while idling? or on the road? If it is idling in your garage, I would say you either have air in the system or inadequate fan. (It's a puller, not a pusher, right?) What is ambient temperature?

 

but you can test for $5.. go to your parts store, get a cheap thermostat, doesn't matter what temp, and cut the bottom off.. install in place of the current tstat..

test..

Sam

 

yes I am cutting one up now just to test er out