Join Date: Oct 2008
Location: South Coast Ontario
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I've never really thought much about hopping up an atomic 4, but now you have me thinking...
A downdraft or sidedraft manifold and carb set up would likely give you some clearance issues. That is the one benefit of the admittedly goofy updraft carb, you can tuck it in beside the block where it is out of the way and approximately 177% more difficult to access.
if you've got the width, a side draft SU might be a decent match, but then you have to create some sort of bellcrank throttle linkage, and then you start scratching your head over the cam set-up, and I don't think anybody does custom bumpsticks for A-4s.
I'd probably look at simply mproving flow by porting, polishing and matchporting the manifold and head, and maybe changing the ratio of the rockers. Maybe deck the head a little to raise compression from the seriously low 6.3:1 . But seriously, if your A-4 will drive your boat at hull speed now, well,...