I have a buddy do this on his 400 just a couple weeks ago, he was tuning it as it had developed a miss... must have been the shreded alum foil that was being spit out the open header.
yes,he has the heads off now doing a VJ on them.
***best way on a BB is to get the felpro HP valley pan with the heat blocked off and use the 4 thin gaskets with it.***
on my SB I have used soup can lids to cut patches out. the MP-block offs are a tad to thick and mine intake bolts kept comeing loose.
I have some thin metal block offs on there now from a radio cover/shell and the 440 has the felpro HP valley pan.
