hello....well if you want the truth about how the lumps work in the exhaust call MIke Kirby-he will tell you ...we can keep saying this and that, but trust me ALL this has been figured out LONG ago...for those who have the Inline Manual you can see the cut away of the head with the work Kirby does....and as Jack has seen, i also have been to Precision Engine Service and seen the exhaust lumps- i even saw the aluminum bolt in 1's he had-but they needed more work to install than just bolt-in ....mmm i even saw heads with them installed and those heads were not cut open....interesting huh?...well i guess you could keep guessing or accept what works and what doesnt-wish i had that much time.... have fun....
Lee
