What do you think of this BBC combo?
 

Gathering up parts to build a big block. Here`s what I have and what I`m thinking of:
1998 454 Gen VI short block.
9.0 : 1 Hypereutectic pistons
Stock rods with ARP bolts
Stock crank
Vortec heads (stock)
Hyd roller cam 230/236 .547/.547 on 112 LC
RPM Air-Gap intake
800 Holley
MSD ignition
Stainless Marine Hi-Torque III exhaust

5200 rpm MAX

Hoping to see 375-385 hp

scrap the hypereutectic pistons for some forged ones and it sounds like a good combo !

Just guessing, you'll make at least 425hp

I have to disagree with my friend 26Scarab on the pistons. I think for what you are running they will be just fine. They will limit you however to how much additional power you may want to add later. Also, I don't think the MSD is required. There are many threads on MSD's on this website, do a little research. I think you will be up ito about 425-440 HP about 500 ft/lbs with that combo you mentioned.
Good luck

Why do I here you guys using Hypereutectic pistons. I feel they should be called "Hyperpathetic". I have seen my share of failed Hyperpathetic pistons. Spend the money go forged.
MikeW

Save your money on the MSD, the stock Mark 4 ignition will be fine. If you really want to add ignition, go Crane HI-6M. Dont forget real big flame arrestor. and plenty of air to the engine compartment.

I guess I need to qualify that with failed in high performance applications.
MikeW

MikeW,
Sure, I will agree that ultimately forged is better than hypernutectics. If you are going to say in the HP range that was described here, a good quality hypernutectic should be fine. The main thing with doing an engine like this is the quality of machine work and attention to detail during assembly. Balance, line bore, use torque plates when finishing the cylinders. Yes, under the wrong application the you can break anything.

I agree with formula31 about the ignition box you won't really need one. When we were dynoing my cousin's 454 with about the same specs as yours---he had the stock Merc distributors (I think they're called the "Thunderbolt"---right?) anyway, we hooked up one of my Crane ignition boxes and made a few pulls and it didn't help one bit for his combination which made 461hp @5100rpm. The only place where an ignition box would help an application like yours is in the idling department, it will idle better, but I don't think you'll need it for that either. BTW, I think you'll be fine with the hyperutectic pistons with your comp ratio,rpm and application. As someone else said; good machine work and attention to detail during assembly is extremely important. Best wishes :)

That is probably just a smidgeon to much cam, with a 454 you will make peak power at about 5500 rpm if you want to prop for 5200 max a slightly smaller duration cam will make more power in the 4500 to 5200 range and more torque from 3500 right on up , that cam would be better suited for a 502

I agree with ursus. That cam is a hair too big....more like 218*/226* or 222*/230* would be more suitable for your application and RPM range of 5200rpm @WOT. Plus it will give you a little more power and not be as lazy in the middle RPM range as well. You're on the right track though. :)

Yes I was thinking of 223/230 like the stock HP500 cam

Whiteknuckle

When I was Teaching for GM we saw a lot of problems with Piston slap with the Hypereutectic ( 91ish 3.1l)after a fair amount of miles.

When we building 450-500 hp BBc with them we had numerous pistons where the pin boss broke off. Thought maybe we where running to tight. So we set them up on the loose side of the tolerance, still had the same problem. I think they just expand and contract to much. I gave up on them after that. Maybe they are better now. After I seen a few Blocks turned to scrap, I will stick with forged in a boat.

Just my opinion

Hey Larry ,
Looks like we disagree on the piston thing, we might have to solve it over BEERS !!!:D

Seriously though I wouldn't put those hyperexploding pistons in my lawnmower! Back in the car days I saw many a guy break those pistons in 400-500 hp small blocks.

Thanks for the input guys!
There seems to be disagreement on:
1. IGNITION.
I have not purchased one yet, so I may save money by finding a good used Merc set-up.

2. PISTONS.
Haven`t bought those either. Forged aren`t much more, but I`m not making that much power. Will probably get forged, just for the insurance.

3. CAMSHAFT.
I was thinking it might be a tad big. I may look at one a step smaller.

Do you guys really think 425hp?
I would be very pleased!!!!!

Ignition:
Your choice , some guys made some good comments about not needing it BUT I've never heard anyone say "well I've got an MSD it's overkill so I think I will change it to a stock Tbolt"
If your not on a real tight budget , what is another $325 (might as well get the distributar too !

Pistons:
GO WITH FORGED ! How do you know what is "to much power " for the hyperjunk pistons ?

Camshaft:
People always seem worried about the camshaft thing, " I might go just a tad smaller" I even said that when putting my motor together ( .723" lift 256/264 @.050 on a 112) but I decided to go with what was recomended and haven't been happier. I've just heard " I should have went bigger " way too many times.

These of course are just my opinions and observations, good luck with whatever you choose.:)

Guys,
On the ignition, a good T-Bolt will run the boat but I always try to upgrade to MSD. If you try to tune a T-Bolt ignition, I don't know any adjustments except initial timing. A six cylinder unit has a much better advance curve and rpm limit. An MSD distributor is a joy to work with and the box helps with idle, plug fouling and starting, but not much at 5000-5500 rpm.
Be sure the components (cap, rotor, wires, plugs, etc.) are good

On pistons, I have had problems with hypereutectic pistons EXCEPT Keith Black. I have seen many of these break in boats and in street cars, but it has ALWAYS been installer error.
Follow the instructions that come with the pistons, not the rings,
for end gap-the top ring gap will be huge compared to what you are used to but do it anyway. The skirt clearance can be relatively small-smaller than forged, but, again, FOLLOW DIRECTIONS!!!!
For the camshaft, I strongly recommend you talk to someone at a reputable cam manufacturer who knows boats, not just the person that answers the phone. A small cam will wimp out and a large one will suck fuel and hurt low speed performance
Hope this helps:D

DonMan,
One thing to keep in mind is there is more to cam selection than just the motor specs. The boat type and hull weight all play an important role. A light boat can use more cam than a heavy boat with the same motor combo. I always have people tell me my cam is to large, and for many of their boats it probably is. My boat is very light and pretty efficient so what my motor is lacking down low is barely noticeable, and there are large gains had on the big end. In my opinion the cam you have chosen is still pretty small and getting the motor to idle and take the throttle crisply may take some minor tweaks, but they will be simple adjustments. Only my opinion! Good luck!

If you really want to gain something worth the money....put these on.

http://www.offshoreonly.com/forums/s...threadid=38575

You will not be disappointed. They will be the best money you can spend.

The heads are pretty well ported and will make 475+ HP easily on a good 454 and unbelievable torque.

Rod

you guys are a little hard on the Hypers Ive got 2 seasons at 9.5 to 1 no problems to date runs damn good dont it Kaama? I saw your Knuckels turn white!!! and the MSD is worth the money to me any day it starts better, idles better ,and gets better fuel economy my .02

Until the MSD screws up, which it will, and then you will be building a new motor. Been there done that seen that. Its amazing how much damage happens to an engine when the advance goes high.

I think I made some wrong assumptions on DonMan's project. His goal was 375 H.P. and I assumed that he was working off a 330 HP block with maybe some budget restraints. If budget in no problem, go with the forged pistons, and MSD. I maintain good engineering is building something that meets your specific goals with a margin of safety. If you go to far past that safety margin, an area of componet strength that the engine will never perform in, you have done things that are not cost effective.

I wouldn`t say my goal is 375hp, I would be happy with that, but would really like to see 415hp, like a 502Mag. I AM working with some budget restraints...Her name is Cheryl.:rolleyes:

RPM, I agree with you 100%. The Merlin oval ports work miracles.
9:1 or even 8.75:1 compression ratio, a good cam, this thing will make at least 425hp. I have built many big blocks and these heads are the best I have run in this type application!

I too will agree that Merlin oval-ports are probably the best head for a big block marine application in the moderate horsepower level. But let`s take a big block designed to make less than 500 hp, aren`t these Vortec heads about as good as you can get before stepping up to aftermarket heads? I already have a nice pair of Vortecs, so I am using them regardless.
I want to run the factory style roller cam, can anyone give me a good recommendation for an aftermarket retro-fit cam? Please give the specs...
It looks like I may be running a 750 Holley instead of the 800...comments?

From the other way....Why would you want to limit rpm to just 5200? If you go with forged pistons and arp bolts, go ahead and spin it 5500. I agree with wette on the cam. I ran a 226/236 112ls on that engine, and it was great for propping at 5500 WOT. This may draw rocks, but go with at least an 800cfm and a single plane intake. Desktop dyno says that alone is worth 40hp over a dual and 750cfm. Just get a straight advance TBV module (v6 or v8) and scrap the MSD, until later. The weak spot I see later on is those little 3/8" rods. They should work fine in your app, I just think they would be one of the first failure points if you push it later on. Heck I pushed the stock cast (300hp) pistons to 600hp blown and didn't have a problem. Never spun it over 5600.

A rough check on desktop, shows ~460hp at 5500-6000rpm.

This is the hp500 cam made/available from crane, make sure you use the right springs

http://dab7.cranecams.com/SpecCard/D....asp?PN=169611

Hypers are fine, Forged for what you are building are overkill
Your estimate of 385 is about right
might see 390-395 but that is about it.
Make sure if you have some advance ground into your cam you are careful setting the timing and the upper end or what these guys said about KaBoom is going to be in your face.
My cam has 4 degrees advance ground in it, Did not know that until dyno day and they put the cam grind # in to the computer.
Jason

Has anyone ever run, or know someone that has run an Edlebrock 454(468 overbore) 540 HP @ 6000 RPM package as shown in their catalogue? It uses a cam with a 112 degree lobe centerline and I'm not sure about reversion. Any help would be appreciated.

I ran a 228/235 @.050 duration hydraulic flat tappet cam ground on a 112 installed on a 108 in a 454 mag with stock exhaust with no reversion. I think this is getting close to the max for stock exhaust. Hope this helps.

I second wette on the experience on the 112, but I didn't think that combo was on a 112?

All you have to do is what I did with the stock exhaust
Get some stainless pipes and weld them in the risers to make a water jacket down towards the back of the boat.
Mine are about 14 inches long welded in each riser pipe.
In essence I have "dry" exhaust and I run a 110 LSA Choppy as **** cam with 7 degrees of overlap
No reversion at all
Jason
best of all this mod cost me about 35 bucks and stainless steel welding rods can be gotten at any welding supply company for a few bones.