420hp 454
 

Around thanksgiving I bought a new to me boat. An 86 242 with a 420hp 454 and Bravo.The motor is a GM 454 with forged steel crank, forged steel ls6 rods and j.e. forged pistons, It has a crane cam with crane gold roller rockers, on GM rectangle port heads, It has a Weiand team G dual plane intake manifold, with a holley carb, ignition is a D.U.I marine H.E.I setup with rev control box. Exhaust is Eddie marine fully polished EMI thunder series manifolds. Runs well and has 90hrs on the engine. I knew I had to replace the swivel pin when I bought it. Upon removal of the transom assembly, the transom assembly turned out to be junk. The transom also ended up needing a total replacement. My brand new transom assembly will be here this week, and i will be finishing the transom soon. So now I don't have the budget to do up the power right now. Anyways, I like to pay cash for everything. I start with a goal, and I buy parts over time. I would like to take my 420hp and turn it into a 550hp. I was talking to Mike Tkach, he suggested AFRs and hyd roller cam. I am open to any combination of parts while using my shortblock. Originally I was thinking slap a 177 blower on and go, but now I am re-thinking that. What is the general consensus here? I want to get my game plan going.

If you went with a blower, I'd go with a 250 blower at least. Many guys have bolted a supercharger on those engines with good results.

88 Bullet was telling me to use a 250 instead of the 177. I was leaning toward the 177 because thats what a 525sc was, so I figured it would be easy to dial in. I am scared of tuning with the larger blowers. I hear 250s with 1 carb, some cylinders go lean. I think 2 carbs might be tricky. I like blower surge though!

would this work well?

http://www.ebay.com/itm/B-M-BB-Chevy...4894f9&vxp=mtr

Yes, that would work. I ran a 250 with a single dominator on my 454's. Dual carbs would be better, but the single 1050 worked. Its a better choice than the 177. I'd definitly want to strip and repaint that blower, and intake in that ebay ad.

Yeah that one looked rough. If it were polished i would own it. Do they still sell new 250 kits?

the only problem i see is the blower will have eaten your budget and you still have crap gm iron heads and a flat tappet camshaft,but it will get you where you want to be.

The blower shop has a nice 250 billet blower kit.

My goal is 550hp. The reason for that goal is to go much faster in a 242 will take alot more power. 550hp will get 70mph, and a bravo should live. When I want to go faster than that I will just buy a faster boat. I am not really dead set on a budget, I would rather have a plan set. Then if I see a good used blower, or good used set of heads, I will pick em up. I am not an expert though. I learn everything the hard way, this time I would rather listen to somebody that already learned the hard way.

So to run this

http://www.theblowershop.com/store/2...ine-p-650.html

I would need to get a second carb, Linkage, fuel line, and flame arrestors, right?

I have a friend Oneanddone on the board. He has a 42 fountain with what were originally 454/425s. Basically same motor you have. They have 250s on top single carb. Boat runs great. Bottom ends are up over 600 hours and have never been out of boat. Heads gone through and cams have been swapped out for Madera cams. Just for info.

So this is the same kinda question I enquired about on another thread.

So if you had some running 420s in need of a light rebuild what would you do for the bang for the buck.?

1st could you go with a Madera cam and open the heads up a little bit and gain 50 horse ?

Or would you slap a blower on it maybe with 2 carbs to get the airflow?

Or upgrade the heads to some AFRs and than call Bob and have a cam ground?