I just swapped 454's in my 71 SS and the new one was a fresh rebuild. The car has the original round temp guage. My old engine ran a constant 180 degrees according to the guage and sometimes if I ran it hard it might creep to 200-210. The new rebuilt engine that I put in, I used the same thermostat and the same temp sensor from the old engine. Now it seems to run 210 and creeps to 230-240 if i am idling through town. My mechanic shot temp readings all over the engine with his infrared temp tool while the guage was reading 210-220 and I cann't remember them all but the top hose out of the engine was 183 and and he said the engine wasn't overheating and not to worry about it. Of course, I just spent $5000 so I am gonna worry about it. any idea why the guage would read hotter with the same thermostat and temp sensor.

tight motor? how new is it?

Brand spankin new. I had it dyno'ed at the shop that did it so they broke in the cam and ran a number of "sessions" I put 25 mile on it yesterday and 100 today. that's it.

Mine did the same thing. Do you run a clutch fan?
Mine was bad replaced mine and it was fine.

fresh,
I dont think it is a "tight" engine. Never have had that situation with a properly rebuilt engine. I am guessing that the new engine is probably making considerably more horsepower than the old tired one. Horsepower = heat. If you did not do anything to the cooling system, that is whay it is runnign warmer.
Just my opinion,

how hot can I let it go before I cause damage?

could the sending unit become "out of calibration" (for lack of a better term) by removing it and re installing it. the infrared sensor says the top hose is 183. that sounds normal.

how can i tell if the clutch is bad?

Here's one way to check the fan clutch: Get the engine good and hot, over 200. Have someone shut the engine off while you watch the fan. It should more or less stop with the engine. It it takes a while to wind down it's no good. At least, that's the way I was taught to do it here in Phoenix.

Tom

Another way to check fan clutches:

http://www.ackits.com/forum/messageview.cfm?catid=21&threadid=10772

I test thermal fan clutches (the only kind worth having) by sound and air flow:

Start the engine from cold, and let it fast idle. The fan will blow, it makes noise, and a guy is tempted to think it's blowing a LOT of air. (It isn't.) Let the engine continue fast idling. As it warms up, at some point the fan will suddenly start making a LOT MORE NOISE AND BLOWING A LOT MORE AIR. You'll think there's a tornado under the hood. There's no mistaking the difference. You could hear it from three car lengths away.

If you cannot get the sudden, dramatic increase in noise and air flow, the clutch is defective. About $50 at NAPA. Don't waste time and money with a non-thermal clutch.

One thing to remember is that if it was bored out over 30 then that may lead to some over heating. Also when you stated you used the same thermostat I believe you used the same type and not reused the same stat, right?

[ 08-23-2004, 03:19 AM: Message edited by: Tom Mobley ]

Jim, fwiw, had my shortblock done, went from 30 to 60 over and bumped dynamic compression a bit ( INADVERTENTLY!), and it defintely runs a bit warmer. Power will do it ( new mill stomps the old one) and going overbore will do it. Trust that you havent set the final jetting, etc either. It may require a bit more fuel, which will, in turn, lower op temp a bit.

200-215 is just fine.

Thanks for the info Gene. I had the block professionally done and dyno'ed at the shop. They fine tuned the carb and timming so it was all read to drop in.

FWIW- it is a number correct set up so i used 820 heads and tried to build it as close to stock as possible. The final dyno run showed 404 HP @4800 rpm and 493 ft/lbs of torque @3000 rpm's. I am very pleased with that an it is very streetable on pump gas. It has a great off idle torque. (as opposed to that LS7 I was struggling with)

Did I miss this somewhere?? But you did bleed all the air out of the cooling system????

good thought....i did not install it but I will ask. thanks.

Check your radiator and make sure it isn't plugged and flowing freely. If it overheats fast, the temp gun won't catch it. I swapped out a 6 with a 327 and it got hot fast according to the factor temp guage. I took it to the shop and had them use the temp gun on it. All was well. We thought it was the guage. We put in a new guage and the new guage read hot. Found out it was the radiator.

i might have a lead on the problem here. My crank pully is some aftermarket billet Al deal. It only measures about 5+ inches diameter. I see the stock ones are 7+ inches. I may not be getting enough flow. I have a stock 3 groove pulley in the shop. I don't have air or PS on the car. which groove drives the water pump? there is 2 small ones and one big one. thanks

On my engine the big groove (closest to radiator) drives the water pump.

BTW how do you remove air from the cooling system?

Yeah, on my 350 the big groove is driving the water pump and the alternator.

To bleed air from the cooling system, start with a cool system, remove the rad cap and insure a good coolant level, start car and let engine warm up till t-stat opens, you can verify this by seeing more flow in the rad through the rad cap hole, let the system circulate while the cap is off and the t-stat open, any air will be purged from the system, its ok to see air gulps and coolant gulping as air is purged. When it settles down, turn off motor, let system cool, top off coolant level leaving a couple inchs for thermal expansion, replace cap and your done.