"Fresh" 360 Overheats

[dartster73]

OK I know I must have done something wrong. When I first fired up my 360 Not only did I have it 180 out I had a couple spark plug wires crossed up. It started and ran BAD....but it ran. I let it go for about 10 seconds before I figured out something was seriously wrong. I sorted out the plug wires and got it lined up to true TDC. Hit the key and it lit immediately and ran awesome. I started my cam break in procedures etc etc. After about a minute and half the temp hit 195 and was climbing fast. I shut it down. Let it cool. All the hoses were in place and the heater is just bypassed. I fired it again. it took about a minute to overheat and blow most of the coolant. So I pulled the thermostat out. Same thing one minute and she was steaming.

Compression is 150-155psi on all cylinders except #4 was 140psi and #2 was 145.

Its a 1977 360 block .040 over, 340 X heads, generic Edelbrock cam and flat top pistons. This is nothing special. I was hoping for some input. Did I blowout the headgasket on the first mismatched run?

[dodger1]

You'll get details from others, but I had the same thing happen to me under virtually the same conditions and engine mods. Apparently the cooling system will trap air on the first fill and overheat pretty easily - sure did when I first started. I managed 15 minutes with the garden hose constantly running into the rad neck and got lucky with the cam/lifter break-in. You might try removing the thermostat next run, and leave the hose in the rad neck. Hope you save your cam!!

[70AARCuda]

Also check to make sure your timing is correct...

[wilks3]

If you drill a 1/8" hole in the thermostat it helps greatly to "burp" the system when filling it up. The hole won't affect the stat at all. This way you will get air out to the top of the radiator where it belongs.

[dartster73]

Thanks Guys, it was a combination of an air bubble in the motor and the timing was set at about 30 degrees retarded. I did the hose trick and was able to cool it down long enough to figure how bad the timing was. I got that straightened out and the temp dropped. Oil temp went down, exhuast temp went down and it sits and idles like a dream.
The scary part was how good it sounded at 30 ATDC