paradigm shift

You really need to decide how much HP and $$$$ are in the budget. Don't forget the drive train if HP and Torque go up so does the strain on the drive.

If you have the blocks and blowers already and need cranks I would go with a 496 combination. If you go with the 1071 non-innercooled and low boost I would say no more the 8.25 cr. Cams depend on budget if you want to go hyd roller or not along with HP you are looking to get. If you go with a blower and are not looking at max HP you have some flexibility with heads and cam set up also to save some $$$$. I think we really need some more info on what your final goal is to go futher. Last thing I have is do not get in a hurry and do the research it can save you $$$$ and some headaches. Just my opinions and I know nothing!.

Wateronthebrain

I want to see 80 to 85 Mph and Have good reliability. My boating season up here is so short, I might only get her out 8 to 10 times a year thus no worries on mileage. She'll sit in the garage for the other 8 months of the year. I'm not running her pinned all the time either.

My total budet for engines is around $20,000. Not the largest,but it should be able to build me some respectable power.

paradigm shift

Sorry I did not get what boat you have and size weight etc. What speed are you seeing now? That will decide how much HP you need.

DYVMASTER

I have stock 1987 420s with Gil Exhaust and TRS drives..would I be able to simply bolt on a set of B&M 174 Superchargers and use my olley 4150 750s I have on the boat now? Or is there some mods to the engine that needs to be done? I know I have rectangular port heads..Crane roller Rockers and hydraulic lifters which I believe all came stock in those motors! I like this thread..Im learning a lot and since my Port engine is out of the boat now I may pull the other and do the upgrades this winter!

badluck

I turned a couple of 420 in to 525SC clones, or Hawk 525SC some years back. I used a B&M 174 with a Holley 850, Imco exhaust and MSD Ignition. I used the stock pistons, new rings, bearings and inconel exhaust valves. Those engines were turn key, I never had any issues with them. I was running 4psi boost.
In your case you would need a bigger carb than a 750 and if you plan to use the stock ignition, you should get a V6 ignition module (less advance). This mod will add 80-100 hp to your 420s.