Led Sled

Hi all... I'm new to the make my boat go a bit faster world. I can't seem to get any straight answers from any one...Water jackets on early "69-85" and late model "86-up" the same? Can I ditch the vortech heads and intake on my 89 5.7 for early style heads and manifold? Any cooling issues? What about valve train geometry? I was planing on the following up grades to speed things up.
1. Through hull exhaust.
2. Good after-market heads "Dart Iron Eagle"
3. Cam and Manifold to match heads
4. MSD ignition
5. Drive shower
6. 14 3/4 x 23 prop

Any susgestions would be great.
Thanks again.

Iggy

No problem swapping the heads and intake. Water passages are the same.

Just remember that the Vortec intake uses a different bolt pattern than the older style (no center bolts).
Actually there are three bolt patterns for the intake. Don't know the manufacturing year but just before the Vortec heads came out the center two intake bolts were drilled on a different angel (straight up, vertical) than the years preceding (perpendicular to intake surface). Be sure you have the correct intake for the heads.

BTW what's wrong with the Vortec heads?
There are many SBC engines making 425+ HP with the Vortec heads. All they need is a little modification to allow a higher lift cam. The Vortec heads also make great torque.

rmbuilder

Try this thread, it may be helpful
http://www.offshoreonly.com/forums/s...ad.php?t=93389
Bob

Led Sled

Thank you much for the quick reply. I have other questions. Do people start a new thread for each question?

Iggy

Not necessary, just add them to this thread if you wish.
If they are on different topics I might consider starting a new one. It'll get more attention that way too.

Bring'em on!

Let me ask a few questions of you:
What boat?
How big?
Type of drive? Alpha or Bravo?
What cam kit did you have in mind?
What intake were you planning?
Carb?
Changing exhaust?
What prop are running now? Need make, model, and pitch.

Led Sled

Thanks Iggy, It's a 1989 IMP 23' with a alpha drive. I don't want to convert to a Bravo "$$". So i was going to put a new set of upper gears, 1.34:1 this i was told is good way of keeping it together, also a drive shower. I do not hole shot the boat ever time I move it if ever " that should help too." The prop now is a 4 blade 14 1/2 X18 SS. As for the intake and cam, I'm looking at the Edelbrock performer RPM package. D234/[email protected] L.539/548 hydraulic roller 1500-6500. I was going to degree the cam to bring down the red line to 5800. 6500 will cook the alpha iv been told. They also have a non roller that is D234/[email protected] and lift is 488/510. A classic 650 Holley vac secondaries will do. Don't for get a MSD to fire this pig up. I want to move prop size to a 14 3/4X23. And finely to let it breath, exhaust straight thought transom. " need advise on best parts for that too"

Thank you
Rob

Iggy

You currently have an 18" pitch prop on it now?
Sounds a bit low for the boat. I have a 1988 21' Formula with a 270hp 350 MAG and an Alpha drive (1.5:1) and I'm spinning a 21" Laser II. Also have a 21" Mirage as a spare.
Is it possible you already have the 1:34:1 gears?

Before you go buying parts you should pick up a copy of "Small-Block Chevy Marine Performance" by Dennis Moore. www.mooreperformance.org
This book will help you pick the right parts.

Iggy

Ok, I went to Edelbrock's site and looked up the cams your considering.
According to Dennis Moore's book the cam you're thinking about is too big for a 350. Crane Cams makes a similar grind and Dennis states that this cam should "only be used in a 383 to 406 in. SBC".
Look at the Chevy p/n 24502586 and Crane p/n 109631.

Led Sled

Hey Iggy, your 100% right about the cam, that would be the best choice.

The GLM exhaust is the ticket as well, nice separation of ports into upper riser and very well built all with a reasonable price.

I checked the prop today, it's like I said. I top out around 40mph @4700rpm. I can't check the gears unless I count the gear teeth. What prop would you recommend?

One last thought is, wouldn't I be better off putting a Whipple or Procharger with 5-7lbs of boost and call it a day? "no other mods except exhaust and ignition."
Thanks
Rob

Iggy

Hmmmm......at 4700/4800 rpm I'm moving at 58-60mph.
You must have a heavy hull. Or does an extra 2 feet of length make that much difference?

Have you tried a different prop just to see what happens? Maybe a 21" 3 blade?
Write down the serial number off the upper gearcase and go to Mercury's Parts Express web site. Enter the S/N and I believe it will tell you what ratio the drive originally came with. Mercuy Parts Express

Tossing a blower onto the stock engine could result in a trashed motor. I don't know how many hours you have on it but without rebuilding it with the proper parts a blower will tear it apart.
If you want to keep the bottom end as is then a cam, heads, intake, ignition, and exhaust is about all you can do. Even then, depending on how worn out the cylinders are, you may not get the full potential out of it without a full rebuild.