endeavour32

iTrader: (4)

You have received some good advice so far, and I will add this to the suggestion pool. First off get with Bob Madera, if you are new to this, ask and we will provide you with in contact information. Second, outside of your compression ratio, your combo that you listed is not suited for a marine engine. Both the cam and heads are more than you can really use, that is if you are buying new and want it optimized.

As for your heads, a 454 needs nothing larger than the AFR 265 oval ports. I ran these on my last engine and I can tell you these are incredible heads. When I bought mine it was $200 more for the CNC Chambers, as Mild Thunder was talking about above. Valako Racing makes a marine head that is even better, but I believe that they are pretty spendy... Rookie, knows about these heads so if you are interested, look him up in here.

Cam- You most certainly want a roller cam, with Morel lifters. IMO nothing bigger than 242, and your lift will be determined by the the flow of your heads.

Exhaust- Search on here for a nice set of used, Stainless Marine, Gil, or CMI manifolds with long tails. Sorry your stock exhaust is worthless in this application. If you are on a real tight budget you can use the stock Merc 496 exhaust but it will hurt you a bit in power output.

The above combo as a 454 will get you around 550 hp, 496 a little over 600 hp. As others have stated, its going to cost around $10,000 for such an engine when all is said and done. Either way, call Bob, tell him your budget and your hp goals and he will get you on the right path. A lot of guys with experience with car engines come in here and will say I did xxx with my 454 drag engine and it made xx hp. This is a boat engine and is a completely different animal. What will live in a car will last 15 minutes in a boat, so it really pays to do things the right way.

TylerBurich

Griff, won't he be leaving a lot of power on the table with the stock style exhaust ports on the edelbrocks?

MILD THUNDER

iTrader: (3)

I am always somewhat perplexed by situations similar to these. Everyone wants to stroke out a 454 to 496 cubes. They will spend thousands on a new rotating assembly, machine work, converting to neutral balance balancer/flywheel, etc. Then, want to use mediocre heads, flat tappet camshafts, etc.

In my opinion, a 454/468ci, with your basic GM steel crank, GM dimple 7/16 rods, is a good foundation for a 600HP engine. Investing the money that went towards a rotating assembly, would have been better served to spend on the top end, like good cylinder heads, roller valvetrain, and a nice induction package.

I guess what I am getting at, is I feel there is more to be gained by going this route, than simply adding 1/4'' to the stroke. Not to mention in a BBC, the valvetrain is the weak point. Invest your money there, and you'll be a happy guy. Cut corners on the valvetrain, and youll be very dissapointed. Just my thoughts.

rotax406

Thanks for the replies I agree money spent in the top end is much better spent I bought this boat cheap with a bad motor the rods and crank were fine and it was already stroked so it made sense to keep it I have cmi power flows but will prob b going with headers mine have a lot of corrosion the only reason I chose that cam was two diff guys used it in a marine build with good results on the dunno 550 at 5800 and 560@3600 torque both seemed to b happy with it im learning so keep it coming I dont wanna dump a hole lot into this boat for The reason if I enjoy it I will be stepping up to a 28 to 31 ft twin im just getting my feet wet per say lol well I hope not wile in the boat lol bob recommends 290 or 305 with his cams might b the way I go and if I go bigger pull the motor and stick a stock one back in to sell cause I will have more in the motor than the boat is worth but sounds like that may b the right direction

MILD THUNDER

iTrader: (3)

Makes sense in your case since it was stroked already. I think I would absolutley go with one of bobs cams, if going with the AFR heads. IMO, a flat tappet, with 575 lift, would be leaving a bunch of power on the table. Those heads will support plenty of lift, and bob's lobe profiles will maximize the setup, not only from a peak HP standpoint, but idle quality, midrange efficiency, etc. That cam you listed, IMO, has too much duration and not enough lift, for a 496 with good flowing heads.

Griff

Sure, they're not CNC'd AFR's, but they cost half as much and he'd be able to upgrade to a matched roller cam with the money saved.

endeavour32

iTrader: (4)

The Edelbrock heads are not 1/2 has much as the 265's. RPM ovals are $1300 each from Jegs. AFR 265 CNC are less than that when I bought mine, and they will smoke an Edelbrock. The only other head I would entertain for a 454 N/A would be Jim Valako's new head. But I believe they are closer to $3000 a pair.

rotax406

I talk to bob he said 290 or 305 with his cam over 600 hp sounds good to me it will cost me about 2500 more than the other way I was gonna go but prob cheaper to do it once and b happy now the question is I raised my drive 1.5 inches what prop should I start with and what kind of mph out of an old 24 outlaw im hoping 70plus

endeavour32

iTrader: (4)

The 290 is a really nice head!

Griff

I was talking about the low hour used Edelbrocks in the swap shop which are listed at $1400 per set vs buying a new set of AFR's.
Looks like they sold a few days ago anyway. http://www.offshoreonly.com/forums/s...rpm-heads.html
His engine is also a 496.