Originally Posted by Scott Dreveny
I have a 78 Bronco and want to Overhaul my tired 400m I would like to get it to 400hp i already have a edelbock 4bbl intake and carb what engine mods do i need to do. Can i keep stock heads just port and polish or do the need to go too. how much of a overbore do i need to go and can i keep my crank what type of cam etc etc etc
We're getting snow up to our butts so I' can't get too deep into this. The 400M suffers mostly from all the things the SMOG engines of that era suffer from; not enough compression, not enough squish quench, and not enough cam timing and lift.
This has caused an otherwise very nice motor to be quite maligned over the years. However, you choose to fix those 3 issues will build you a 400 plus HP motor. Everything else is just prettying it up from porting, to headers, not that those things aren't needed, but if the first three don't get fixed the others will never be as effective as you'd wish for in terms of building power.