87MagnumII

Ok I know I should have stroked this dude to begin with but I was being cheap and didn't do it. Here is what I've got

1997 350 CID
Vortec heads
Lt4 hot cam
1.6 roller rockers
9.8:1 compression
Performer rpm intake
650 demon carb
Block is decked
Crank is balanced

This package will turn 5000-5200 rpm thru a 1.47 alpha drive with a 21 laser II at 60-63 mph

Here are my questions

1. How tight could I twist it if I turned it into a 383
2. Considering all labor and machine work are free I just need to buy parts to stroke it, would there be enough of a gain to worry about?

3. Would a 383 setup turn a 23-25 pitch prop up to 5000-5200

sprink58

Dave,

Understanding "Free labor and machine work"...leave the 350 the way it is. Find a 400 cu in SBC..go 030 over and build a 406 with Vortec Heads and a torque cam.

I built one years ago in the "Pre Vortec" days using "186 Double Hump" 2.02 factory fulie heads w/64 cc chambers, dished pistons to keep it at at 9.5:1, a 350 HP/327 Crane "Blue Print" of the Chevy Cam, Chevy LT-1 square bore intake with a 750 Double Pumper, MSD 6A. The engine dynoed at 435 HP at 5600 RPM and made over 400 lb ft from 1800 RPM to over 4000...peak was 455 at 3500!!

With the new Vortec heads you will probably do better

Pull the 350 and sell it after you drop in the 406. You won't be thinking about spinning it more...you'll be trying to bite more water with a bigger prop.

Just my thoughts....I want to put a pair of those together for my 255.

Griswald

To answer your questions:

You can spin a 383 as tight as you want. Good crank and rods, run a good balancer and let it eat.

You're gaining torque by stroking it and torque is king. Worth every penny. That doesn't mean you're going to realize a huge mph gain though.

87MagnumII

I'm running 60-62ish now, if I can get 65-66 I'll be a happy camper, was just wondering if turning it into a 383 would get me there

87MagnumII

I'm trying to stay on a "budget" (I know boats and budgets don't mix,lol) with this thing. I can do the stroked kit for around $1000 so that's what I'm leaning towards. I know a few guys running 400's and they love them but I'm not really wanting to start from scratch again

jason4636

I have a 2003 Crownline 202lpx. 3400lbs boat with alpha 1 gen 2 outdrive. I blew my lower half of the outdrive in 5 hrs with new motor. Put a new SEI lower on it, and have been fine for 25 hrs so far.
On the motor I have 383sbc. Eagle forged crank,and rods, JE forged piston, AFR 190 vortec heads, Lunati 60121 cam, with roller lifters and 1.6 roller rockers, Edelbrock RPM air gap intake, Holley 750 carb, holley blue fuel pump, EMI Thunder exhaust. And a lot of other stuff. Total of $12,000.

On the Dyno I only did my pulls from 2700-5500 Rpm's
482.7 HP at 5500 Rpm and still climbing
486.7 TQ at 4300 Rpm
At the start of my pull at 2700 rpm I already have 433 TQ, and still at 5500 I still have 460 TQ. Its a real flat TQ curve.

The Boat runs 65 MPH at 5300rpm with a Merc. Rev-4 19P
Heres a link to my cam
http://www.lunatipower.com/Product.aspx?id=2011

Hope this helps you out

jason4636

The only reason I spent so much on this motor. Is because, the factory motor was messed up when I bought the boat. So I rebuilt the motor on the cheap for $3000 to a 383 with all cast bottom end. It lasted 22 Hrs before it went.

So I bought everything brand new including the block. I wanted a motor to be built like a brick **** house. I know I probly payed way to much for a boat motor, but I like peace of mind.

Dennis Moore

The difference between a 350 and a 383 could be seen as the difference between a 327 and a 350. The only difference is 1/4" in stroke. Not much really!
I wonder if two identical engines were built (with only a 1/4" difference in stroke) and dynoed, if the power would increase by more than 10 horsepower? 15 horsepower? Doubt it would be more than that!
How much work and money are you willing to invest for 10-15 horsepower?
Will a 10-15 horsepower increase require a higher pitch prop?
Dennis

SB

iTrader: (1)

1hp per cid is very easy to get now-a-days.

So, quick easy to see example:
1hp X 350cid = 350HP
1 HP X 383cid = 383HP.

Many boats with small blocks are very light and run fast. Many don't. Which do you have ?

33hp in a small lightweight I/O with quick bottom is gold !
33hp in a big wave pushing 'tug' may not be worth it.

I have and run with a few people with light (under 3k lbs), quick bottom, 18-21 single 350 SBC boats that respond to pretty much anything - positive or negative.

Would you believe almost 3mph with a GM cast iron high rise intake on bone stock 5.7L 260hp Merc in one of them ? Still quadrajet carb ?

SO........yes, small hp improvements can be well worth it. Making a 260hp motor into a 330-350hp motor can be well worth it ! Well, well worth it. So........yes, going to a 383 and making even more power can be super worth it.

It depends on your boat and your boat tuning abilities.

BTW: Yes, my hands get dirty. They are dirty right now. Not just an internet keyboard guy. I can be sometimes though. LOL.

SB

iTrader: (1)

Interesting as many people with same combo (less compression) turn a 23" 5000rpm with same engine combo. Speeds in 62-65mph range. Exception would be a 21 Velocity that will gover 70mph with that package. Again, a large exception as those boats haul with their respective power.

Is your boat heavy ? Not a performance (quick) hull ?

Stock exhaust ? Too small flame arrestor ?

Have you tweaked your BG650 ? What spring do you have in the secondaries ? I've used same carb on just about same engine build and found stock jetting to be almost right on. 700ft above sea level. I, however, spent better part of a day tuning with secondary springs. Believe it or not, ended up accelerating the fastest and getting best top speed with the lightest spring in the kit. SHort/soft yellow one. I crapped (lol) with the difference. Yes, was armed with a GPS...no butt dyno stuff here.

So, if you haven't done atleast that, your carb has a quick change spring kit on it. It's the big red round thing with a slot in the middle. Just turn it counterclockwise with a decent size flat bladed screwdriver until it unthreads. Wallah, there's the spring.

Keep adding softer springs until your grin is the largest. If a softer one slows it down, go back to the last 'best' spring.