I have a 81 Nordic 20 with a berkley jet. I have built several car engines but this is my first marine. My engine is a 4 bolt main 60 over 454 stroked to 496 with scat forged crank, rods and wiesco +30cc pistons all balanced. With my 292 heads I'm now afraid I will have to much compression for my boat. What do you think? Also i don't have a cam yet. Im worried about reversion with my basset water injected through transom headers, air gap single plane intake and a 750 holley Msd distributor and Msd box.
High compression isn't a problem.. just have to run good fuel and keep the timing under control(right close to 36* total).. big HP is fun.. and with the weight of your 20' boat.. the more the better..
H20MOFO is right.. get a spring loaded valve inline with the water cooled headers that only allows water into the headers after 2K rpm.. spring pressure is key.. play with it, as rpms increase, so does the water pressure at the pump.. so you'll need to dial that in..
Like to also say... a BBC with close to 500CI.. needs a bigger carb than a 750DP Holley.. go bigger... a 2-circuit 950-1050CFM Holley would be my choice...depending on the cam and the rpm you plan to run it at.. going to run mine to 7400rpm MAX..
I am running the same basic 496 combo, right around 650HP.. stroked MKIV 454 with 088 GenV heads(open chamber rectangular ports) w/2.25" intake valves and 39cc SRP Forged Pistons..
12.07:1 and it lives on 100LL Avgas... pretty blue fuel @ 6.00 a gallon... might look into E-85 @ 2.78 a gallon... cheaper but burns 30% more fuel than the blue stuff... so will have a shorter cruise capacity, just have to carry more fuel with you when you take it out.. any way you look at it.. it needs higher octane than pump Premium to keep it happy..
Cam is 271/282 @ .050" Duration Comp Solid Roller w/.680" lift, easy on the valve train.. AR306-10..
Single Plane Team G manifold and an 1150 Holley Dominator... dry "Rewarder" headers.. have fun!
Last edited by Old as Dirt; 09-14-2015 at 12:32 PM.