Finding cracked block/head

[Fast Ed]

I have a 1996 5.7 Vortec converted to carb. It runs good. Stays cool- 170! It must have a cracked block or head. It keeps getting lots of brown sludge in the radiator. Also has small bubbles when running with radiator cap off. I'm trying to determine if it is a head or the block? Any ideas?

 

[gpmorgan]

Remove the spark plugs and see if one ore more are extra clean. If so, it's probably the head gasket or possibly cracked head. I've heard those engines are prone to crack the heads??? You can also do a compression test to find which cyl is having the issue.

 

[Honky Kong jr]

X2^^^^^^

 

[4WDKC]

If you take them off for any reason have them magnafluxed and pressure checked for cracks. I bought some from a running motor no coolant in oil and one had a hairline fracture that didnt leak but the shop didnt trust it and said first time it got close to overheating it probably would have become a crack.