I have a ~325hp 331 that's .030" over, with about 25k mi on the build I also run 60/40 water/coolant, with a bottle of water wetter.

 

yeah, the .030 over is what is saving you . . even with 300 hp you can run a 3 row with a good clutch fan . . the .040" makes them marginal then blocking the air with a condenser makes them run hot, then you turn the ac on and run hot air into the rad just makes it roast.

 

is that HP at the engine or rear wheels?

 

Probably motor. I'm guesstimating the output, heh. My engine analyzer program says 350, but it's probably a bit optimistic...

 

do you mean computer program?

if so, the dyno 2000 is decent, especially if you have all the upgrades but it is still a bit optimistic.

the free comp cam program is typically around 30% high on fords.

most real dynos are inaccurate because they are designed to read inaccurately . . a mustang dyno is more accurate than all but one other that i know of and if you get 300 hp on the west tech dyno, it will surely be around 220 on the mustang dyno.

for this reason, dynos are only good for comparing different parts and settings.

 

I picked the Mustang up from the shop on Tuesday so I drove it to work today. The needle got just above the "C" and held steady. It was about 55 degrees out and the traffic was ok. I had the shop flush the system and install a new thermostat. I still plan to put in a 6-blade fan and shroud but seeing how cool it ran today I'm not too worried anymore.

 

i hope they installed a 180 thru 192 degree t stat.

i would drain fluid out until i could see the tops of the tubes thru the rad cap hole and see if there is any rust coming out of any of the tubes you can see.

 

Something is very wrong if the needle is staying just above the "C"! It should be around the halfway mark once the engine is at normal operating temp (thermostat specified temp., a 192* is original equipment).

 

I marked a red line on the pic at right about where the needle stayed during my ~25min commute.

 

thats about where mine runs.

I installed a real temp gauge and found that to be about 198F middle is about 210...Doesnt mean its the same in your case.

-Gun