Rebuilt 455 in an omega aluminum radiator, headers, new coolant, new thermostat, everything new! It runs for 5-7 minutes then climbs to 220, thermostat opens @200 drops to 180 then climbs to 220. No air in the system as far as I can tell burped it ten times or so. I have 2X10" fans pushing from the front and the original blade fan on it also still overheats. Very frustrated! Please help lol no really! Thanks

 

May need a bigger radiator how many cores do you have

 

If the temperature changes are very rapid you still have air in the system. I usually stick a water hose with a low flow in the neck of the radiator and force the bubble out once the thermostat opens.

 

Have you verified your temp? I find these handy

 

It's a 3 core. I know new motors create more friction but I can't even run it long enough to break in the new cam. Maybe a colder thermostat 160?

 

A cooler thermostat won't help as the one you have is fully open at the operating temp you posted. All a lower t-stat would do is open sooner but the temps would still get above the opening point.

Overheating boils down to the engine is generating more heat than the cooling system can dissipate. You need to find out which part of the system is not operating up to the necessary level, whether that is the heat transfer of the radiator, the flow rate of the water pump, or the air flow rate across the radiator. One of these is not sufficient to dissipate the heat that the engine is producing.

 

Sounds like you still have an air lock as Eric said, If you have a 180- 195 thermostat you should be fine 3 row rads take a bit of time to get the flow going properly. I wouldn't go below a 180. Have you checked the water pump?

 

Puller fans in a shroud that fits the radiator work better than just 2 10" pushers on the front.

 

Do you have a fan shroud in place? Have you verified the temps? If your gauge is off only 10% you're about right on temperatures. Shroud properly in place around puller fan with good clutch and fan the correct depth in shroud should run at normal temps. Good luck!
DW

 

X2 on the water pump and I know this may sound very elementary but it the belt tight. It is one of those things that is easy to overlook when you are putting an engine together.

 

I would double check timing and jetting.

 

You could try placing a shop fan in front of car, if this holds the temp steady you can break in the cam..

 

One of the many things I like about this forum is all the knowledge you gather from everyone through years of wisdom..you can't put a price tag on it..I don't have anymore to add..

 

It's a 3 core radiator all aluminum I think it's to small they said its for a big block but I check their site and it says sbc. I'm gonna rent a large fan this weekend and try it agin and hope for the best. I haven't verified the temp yet but each time it's extremely hot top hose is like a rock and it shoots coolant out the reservoir tube. It won't idle but over 2k she runs as smooth as could be, stumbles and dies under 1500rpm and hard to start unless WOT. I lost the shroud in my move.

 

You have to get the timing correct, you have to make sure you have no air leaks pulling thru the carb base or manifold, you have to make sure your fuel mixture is correct and as said before no air in block or you won't get proper circulation..use a 50/50 mix..find a fan shroud they are out there and run a thermostat..headers generate a lot of heat and hard to dissipate so you need to get that engine cool..becareful not to run to hot or you can crack those heads.

 

The base timing is correct everything was checked and rechecked a dozen times prior to the first start up. It had tiny little paper thin shavings in the coolant after the first run I was thinking maybe from the machine shop? We flushed it again and put 50/50 mixture in again. Oil pressure stays between 55-60 from start to finish of the run. No knocks or grinding leaks or anything out of the ordinary but this is my first fresh rebuilt motor. Maybe a larger radiator? The one that's in there is only 28 overall width

 

Radiator may be ok at that size being aluminum and 3 row however you need to have the fan pulling a vacuum thru radiator.. By getting the engine fan as close to the radiator as possible and have a shroud to help cool the the fluid inside radiator and pull air thru to also cool engine.

 

When using a fan shroud, you don't want the fan as close to the radiator as possible--you want it half in and half out of the shroud. Most of the air pulled by the fan is slung off the ends of the fan blades and it will pull multiple times as much this way as up really close to the radiator. It creates a turbulence inside the shroud that slows down the air flow.
dw

 

A 3 row rad is plenty big anuf, As others mentioned you need a shroud, a 1 inch spacer under that carb would help too. Can you see the coolant flow thru the tubes with the cap off? Is the water pump new? High flow?

 

I would focus on radiator, you said you had metal shavings, great for plugging passageways and blocking flow thru radiator.

 

Pusher fans with factory fan just obstruct flow. Idles in Florida traffic with A/C, never gets too warm.

 

Your radiator should be able to cope with low load breaking in running, pulling up a long incline or idling in traffic in 100 degree weather would test a radiator much harder.
Here's another approach to your problem; it could be you have a bad head gasket, you won't necessarily get milky oil and you haven't run the engine for long. But you will get the symptoms you describe. You won't burp the system if it is being pressurised from a gasket leak.
Fitting a shroud is a must imo, as has been pointed out, you need to place the fan half in the shroud opening, and keep a thermostat in the system.




Roger

 

I had the Champion 3 core in my Cutlass, didn't cool as well as the Modine single core even. I put in an EBay special two core, bigger all around and cools better. Get a bigger rad, like the Griffin Dominator, 2 big cores, US made and affordable. Get rid of the pusher fans, get the big Derale US made big dual pullers, supposed move a ton of air and affordable too. Also make sure your thermostat is fully opening, I had a Mr Gasket high flow that didn't and just got worse over time. If you have under drive pulleys, throw them in the bush. That is all.