Allright guys I have a set of each. I searched old posts about the differences but couldn't find any info on the 2. Whats the differences, I've read the combustion chanbers are the same. Why port one set over the over?

I'm taking a set to the machine shop today. Thanks in advance for the input.

 

Use the 241s they can use the gm mls gasket while the 853s have to use graphite and the 241s are marginally better for flow.

 

Why do you have to use graphite with the 853's. I have never heard of that.