The 308's i have had alredy been polished, so as cast I cant say...
I can tell that the polished 'with nothing else done to them' 308's i have flow 232cfm.
The stock 2.02 J's I have 'as cast' flow 228cfm.....so it's close but it could be the polishing imo..cause the port looks IDENTICAL in every way except for the the push rod pinch being more intrusive...which kinda tells me the push rod pinch is not an issue in stock form, so in that case... to work that area of the port 'push rod pinch' would be simply slowing the air down...and counter productive, even if it yeilds 3 cfm more.
As for the exhaust...they flow more at the lower lift, after that.. the roof is cast so low that just a lil port work is required...then they flow big, compared to a lot of port work to get about the same with an older head, simply is in better form to start with.
back on topic..
After I do the next round of numbers for these 318 heads, I will start on the exhaust ..stock and modified with step by step pics.
