atkinsom

I just put in a 455 using the autometer mechanical temp gauge that I had used in the 350 previously. The gauge is giving some crazy readings when driving going from 190 to 210 235 and then down to 200 185. It bounces around while driving yet under park the temp stays at or near 190. An infrared gun shows the temp steady at 186-190. The tstat is a brand new 180 degree that was used as well. I'm a little nervous seeing this but if the motor was going to 235 i would expect it to implode almost right away and start to stumble? It's freaking me out because it was pretty steady with the 350 before the swap.

Any suggestions or tests i can try?

1969 455 bored 30 over
edelbrock 04b manifold
gauge sensor in water jacket port right beside the tstat housing with no leaks.

oldcutlass

What you probably have is a very big air pocket. Let it cool a little to get the cap off, and stuff a water hose with a slow flow in the water neck of the radiator and force it out.

atkinsom

So to get this right. Start the car and let it warm up to temp in the driveway. Turn it off and let it cool to the point I can get the cap off. Then take a garden hose, stuff it into the open hole of the rad and start the water at a very slow rate. How far down do I stuff the hose into the open hole of the rad? and how long do I do this until the air pocket is cleared since I assume rad fluid will start overflowing like crazy? The car has an overflow bottle as well that's empty right now...4 core rad as well. Sorry for the newb questions and thanks

oldcutlass

If the engine is cool, start it and let the thermostat open. Turn the hose on to a slow flow and stick the end in the radiator and turn it on until you see the air pocket bubble out and the temp gauge reads steady.

bigoldscruiser

The air might escape easier if you just loosen the gauge fitting enough to let some air/water out.

atkinsom

I think I got the air pockets out but at what level should the rad fluid be at in the 4 core GM rad when cold relative to the neck on the side? I filled the overflow recovery tank to the cold level but confused what level in the rad itself thanks

oldcutlass

Just put the cap on and make sure the recovery tank is filled to the normal level, it will maintain the level of the radiator correctly if it has the correct radiator cap on it. It should stay full to the top.

atkinsom

One last question...the recovery reservoir has an add and full hot markers. It says on the top of the recovery reservoir to check hot. I noticed today that the rad fluid after it had cooled was well below the add mark on the reservoir but when I popped the cap off the radiator itself it was full right to the top...should I add more rad fluid to the reservoir add marker or just leave it alone. Thanks guys.

oldcutlass

Fluid will move in and out of the recovery tank as the radiator heats up and cools. With the tank installed the radiator level will be full at all times. I would maintain the level of the tank so it's at the full line when it's hot. It will be lower when it cools.