blowing white smoke at idle intermittently
 

I have a 95 z-28 which I justed purchased from a friend. It just starated puffing white smoke at idle nothing during cruise. performed a block test and came up with no hydro-carbon in the cooling system. where/how can coolant be entering the combustion chamber..... no misfires, plugs look okay.... and yes its defenitely burning coolant has that crappy sweet smell. any help????

just an idea...
i have heard of cracks in the throttle body allowing coolant into the system and that would obviously pass a block test

Thats the next thing I am going to check, thanks

It may not be coolant. Oil from one or two valve seals?

no, Impretty sure its coolant. removed the t-body,no signs of cracks. guess the head gaskets are starting to go. How prone to head gasket failure are these motors?