i was lookin under the hood tryin to figure out what heads i have and i seen a casting number of 706 then i looked on my brother 2011 truck and he has 243 do these numbers mean anything ? and if im gonna have a set ported polished and flowed which do i want and which do i want to stay away from ?

 

what i was thinkin was should port my or get a set from the salvage yard for cheap but what casting nummbers

 

the 243 heads are very nice but would lower compression on a LM7 5.3 due to the larger combustion chamber so some milling would be necessary. Your brother's truck has different pistons allowing for that larger combustion chamber.

 

get the 243's milled.

 

+1, they are the more desirable castings

 

yup, and iirc, 706s had problems with cracking and breaking?

 

I believe that there were some early castings that were prone to cracking, there are pictures floating around here somewhere that show the casting mark to look out for on the bad ones.

 

thanks fellas. now i know what to look for