[tpssonic]

Originally Posted by Cliff R

We usually have trouble getting them to heat up rather than overheat. My current 455 is the worst one I've had in the car, it takes FOREVER to get up to temperature, and can be a real PITA to race the car in the cool Fall months as I have to leave it idling in staging lanes to keep it up to temp.

We've determined that these engine LOVE super tight squish. Combine that with very well chosen camshafts, and careful tuning, and you'll have a Pontiac engine that makes great power and never even thinks about running hot/overheating for any reason......Cliff

X2!

[Blued and Painted]

Originally Posted by crm318

putting a 1/4 npt pipe plug in the bypass from the crossover to the pump and drilling a hole in it? Does it increase coolant velocity?

it will reduce by-pass coolant and force a greater volume/percentage thru the radiator. Drill plug too .250..

[Schurkey]

Originally Posted by Cliff R

We've determined that these engine LOVE super tight squish.

I'd love to hear what you consider "super tight squish", along with your rod/piston combo (material, weight, piston-to-bore clearance, etc.)

I think I put Father-In-Law's 455 together with .045 squish/quench; but only because my machinist didn't follow my instructions to ZERO-DECK the block. He got it to .005 in the hole. I was shooting for .038--.040 squish.

Apparently I was too conservative...I assume you're running less than .040.

[Ben M.]

My '73 runs at 190F in the head all the time... except when sitting at a stoplight for more than 20 minutes with the AC on when the outside ambient is above 95F. It crept up to 210ish. My clutch fan could be stronger I guess... But then my modern cars don't exactly like to sit at idle with the AC on for 20+ minutes either!

[STEELCITYFIREBIRD]

A toilet overflows, but only when it's stuffed full of chit.

So don't stuff your car full of chit, and it won't overheat.

[goatwgn]

Originally Posted by Torquewar

Good points ...match things properly. Tune is very important .
Good rad, not some untouched junk stored for 40 yrs. Divider plate clearance and a proper shroud.
Too much info out there to have a hot running vehicle today. It takes some research.
I can run mine in the hottest humid days and never creep over 190. This summer was a true test .
461 /78 TA that has run 11:40s 50s

X2. A combination of things being "right" as they actually were set up at the factory, as well as a sensible compression ratio, or a cam that bleeds off excess pressure, can keep the car running cool. My 455 in my '66 never goes up above 195 in hot humid high traffic conditions with the AC on. It stays at 180 all winter or any condition I don't run the AC. I run a 180 Thermostat, factory style flex fan (Ram Air type) with shroud, smaller water pump pulley with properly clearanced water pump, large 2 1 and 1/2 inch core aluminum radiator (painted black to look factory) and 9.3 to 1 compression. The car did run hotter when I had higher compression no 62 heads on it. Had to run retarded timing, and this drove up the heat. This engine combo runs 4X heads, and 32 degrees total timing with functional vacuum advance and never tries to overheat.

[AG]

I have a '72 vert with the stock 350 2 bbl radiator in it with a 455 with 9:1 CR and a 160 F T-stat and flex fan. Car only gets up to 170 F on a 90 +F day regardless of driving conditions. I have to put in a 180 F T-stat so It will get to a higher temp. In the fall it doesn't get above 140 F.

[Schurkey]

Originally Posted by AG

I have a '72 vert with the stock 350 2 bbl radiator in it with a 455 with 9:1 CR and a 160 F T-stat and flex fan. Car only gets up to 170 F on a 90 +F day regardless of driving conditions. I have to put in a 180 F T-stat so It will get to a higher temp. In the fall it doesn't get above 140 F.

Have you verified the temp gauge for accuracy? It seems unlikely that an engine would run at a lower temperature than a properly-functioning thermostat.

Your cooling system seems "too good to be true"; which could be worth some investigation.

[AG]

I haven't verified the temp with another gauge, but before I put the flex fan on, I had a Hayden severe duty clutch with a factory 7 blade fan. The car would get over 210 F on a hot day idling which is why I replaced the clutch fan. I had the flex fan sitting around and tried it to see what happened.