I figure with some down time this winter it may be the right time to give the cruiser a little more pep.  I figure another 100 hp would be a good target to work for (~500hp).  Currently everything works flawless, I'm just kicking the ideas around.  I hate to tear down something that works, but more is always better!

The engine is a '96 Marine Power 454 ~390 hp (spinning an A ~4800-4900), forged pistons, new gm hi-perf sq port heads, rpm type intake, q-jet carb (works for now), 9.5:1 compression.  Pump gas is a must and not squeezing.

What are the options without tearing though everything?  Blower... too much compression?  Stroke it to a 496?  If so, what are your estimates on the build  $    Any help   


Thanks!

pro charger

A good set of cylinder (aluminum) heads , cam and 850 carb.

-beerjet-

    

Get your current heads flow benched and optimized, new cam and good set of roller everything, RPM airgap manifold, new carb. Carb is the expensive part. Unless you're really trying to save weight, don't waste your money on the aluminum heads.

As far as the centrifugal supercharger you can probably run 7lbs comfortably and still just run 91. If you put a real supercharger on there, same story 17% underdriven should give you about 6 lbs of boost. That 6 pounds will give you a clean 125HP. Slap two 600 Holley's on there a new cam and roller everything, have your heads reworked and you'll be gold. Probably closer to 550HP conservatively.

What's the casting # on the heads?
Put a solid roller in it .680 lift with about 260 durration at 50. Instead of a carb, I'd run carbs.
I had a similar combo that made just under 600 hp with a flat tappet cam. Boat ran 83 mph!!

As far as I know there is still no aluminum Y Block head. I was helping in making one, but it's stilll not available

I seriously doubt that by only stroking the engine out will it get you 100 HP. He's making less than one HP per cubic inche so by stroking it to a 496 it should theoretically gain him... about 36 more HP. Even if he bumped up the compression a point, which may stop him from using pump gas, he'd still be under his 100 HP more goal.

If you look at the cost of decent aluminum heads, combined with the potential to increase air flow more at a later date, plus they're aluminum which (supposedly) helps control detonation, not to mention they look SIK, why bother with 20 or 30 year old cast iron heads?

It's difficult, at best, to argue with a blower engine. However consider that a blower will reduce the life span of the engine signifantly.

I'm still leaning towards a decent set of aluminum heads, a "bigger" cam, and a Holley DP. If you got the $ definately go roller cam.

How much for the aluminum heads? Then you gotta worry about electrolysis. Doesn't really sound like this guy is someone who's is ready to do a lot of tuning and maintenance. You're not gonna want to pass up much more than 500HP. You've got to consider your pump too. Some guys insist on running an aluminum impeller all the way up to 1000HP but you're eventually going to spin the center right out of the impeller. Just can't exactly dump on it at low speeds. You've got to be ready to make the commitment to your pump too, not just the engine...

Easy power, since you're not willing to buy new heads (as you said you just bought these ones) I know two different guys who will both do a great job for $500 or less. Get a Hydro-roller cam and roller everything package from Comp or Crane (preference is up to you), find a used RPM airgap manifold on ebay or something, and an 850 carb. I'm partial to Demon's. Had a 1050 Dominator on my truck and had to adjust it constantly, 950 Demon tweaked it once and it ran great all season.

If you're looking turn key, stick with the single carb.


What kind of boat is this going in?

Thanks for the feedback.  There's tons of info available from this boards' members!

This is going in a big hawaiian... a cruiser (below).  "Plug and Play" would be best because of my limited knowledge and experience.  I'm not afraid to learn, I'm just doing so as I go along.   


As for the heads, I found the part number and info on the net.  These were new and fully assembled:

12562920 Cast Iron Gen V & VI Cylinder Head Assembly Gen V and VI cast iron head with 118cc open chambers, rectangular intake ports, and 3/8-inch rocker stud holes. 2.18-inch intake valves, 1.88- inch exhaust valves.



What does a set a Al heads cost?  Ah, never mind, probably would have been a better idea to spend the money then -when I didn't have it!  So about porting the existing heads, what gains would be see with a mild cam?  Cost/labor?

So...
Port existing heads  $?
Roller kit + Cam   $?
Holley dp 850   $300 to $500


The pump should be in great shape.  It was completely gone through last year from a new drive shaft to new impeller (just about end to end!)  I'm thinking towards a AA to pull the rpm's down on the long hauls and give a bit more out of the hole.  This boat can use a stump puller!  I'm finally licking my wounds after buying the boat a year and a half ago, running it for a couple hours, then in the shop for the next few months.  I took all the funds away which I was hoping to spend on the fun stuff a year ago...


Thanks
LC


big jet.

...  These were new and fully assembled:
12562920 Cast Iron Gen V & VI Cylinder Head Assembly Gen V and VI cast iron head with 118cc open chambers, rectangular intake ports, and 3/8-inch rocker stud holes. 2.18-inch intake valves, 1.88- inch exhaust valves.
...

(From what I've read) Those are some really good numbers for a Chevrolet stock head. Ditch my suggestion of switching to aluminum heads. The combustion chamber is not too big and not too small, couldn't ask for better flow (stock) than rectangular ports, real good valve sizes... plenty of air flow potential for some real good HP.

An engine is an air pump and with Chevrolet the stock heads are what usually limits the HP, your heads ain't limiting jack sh!t at this point. Much bigger cam (roller preferred), Holley DP (or two), and you'll have your 100 HP addition. I wouldn't even port the heads you have.

You wrote you're thinking of going to a "AA" impellor to lower the RPM's, what RPM are you at W.O.T.? Going to a roller cam will significantly raise your redline thereby not making it nesessary for you to lower the RPM's at W.O.T.


IMO

I dis agree on the carb set up! I have a tunnel with dual 750's on a stock motor and have never had to touch them once since I got them back from the carb guy. Just do yourself a huge favor and make sure you get matched carbs ment to be ran togeather , not just two of the same kind.

I dis agree on the carb set up! I have a tunnel with dual 750's on a stock motor and have never had to touch them once since I got them back from the carb guy. Just do yourself a huge favor and make sure you get matched carbs ment to be ran togeather , not just two of the same kind.

Legal Chemistry may want all of the info on your "never been touched" tunnel ram set-up. Not to jump on your back or throw you under the bus but... I read nothing in the above post that tells the story of 3' flames shooting out of your two carbs! I saw it more than just a few times. Maybe he doesn't want flame thrower's serving as carbs 

As far as the "matched carbs" and "not just two of the same kind", I'm calling BULLSH!T. If you are refering to the two carbs needing to have the same jet sizes, accelerator pumps, etc... then yes, a matched set is required. BUT if you are refering to "matched set" of carbs built by Holley with different metering blocks and all of that other crap you saw on TV - BULLSH!T.