383 stroker is it worth it?

[Bondo]

Yes many people to you are right. But when all hell brakes loose it becomes quite pricey. IMO anyone knows someone running anything bigger than 5.7's to R,MR, or Alpha drives is tempting fate. Those who have done it and are successful will fall short eventually as their luck runs out. It's inevitable.

Ayuh,..... SEI drives are 'bout $1,500. brand new with a no questions asked policy,.....

Chump change in the Boatin' world, so long as yer turnin' yer own wrenches,.....

 

[Walt T]

I built a 454 for a guy who used an SEI drive. Last I heard it was still going strong. Yes the 290 isnt an apples to apples comparison. I simply told him my experience with the engine. You can put whatever you want in there and it'll be fine if you baby it. But then why even bother.

 

[flipbro]

Haha no drive switching in my future. I know these drives and learn more all the time lm merc all the way... My boat is a 20 foot wellcraft elite BR very lite. I think I will go with the vortec heads a eldibrock doul plane mabe the air gap version machined to get the center bolts and a nice cam any suggestions on the cam? I plan on keeping my QJ Carb as its been rebuilt and works absolutly beautiful I know I will need an adapter plate if memory serves me..

 

[achris]

Haha no drive switching in my future. I know these drives and learn more all the time lm merc all the way... My boat is a 20 foot wellcraft elite BR very lite. I think I will go with the vortec heads a eldibrock doul plane mabe the air gap version machined to get the center bolts and a nice cam any suggestions on the cam? I plan on keeping my QJ Carb as its been rebuilt and works absolutly beautiful I know I will need an adapter plate if memory serves me..

Best plan I've seen yet... The 2516 (http://www.edelbrock.com/automotive/mc/manifolds/marine.shtml) intake will accept both square and spreadbore carbs.

 

[NHGuy]

I don't think an air gap intake gains much in a boat, because they already run a bit cool, mine has a 140 degree stat...

I'm really happy with the Comp XM262H cam, here's a link...http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=99&sb=2. Just be careful of valve lift values. GM Vortec heads have a limit on lift beyond which you'd need some machine work. There are aftermarket heads with vortec chambers that may do the job for you with no machine work. Search around a bit, some of them could even accommodate your old type intake manifold. I used my original pre vortec (swirl port?) 64cc heads and did aluminum standard lift roller rockers, and a kit from Comp that included the cam, lifters, valve springs, retainers and keepers. It needed the springs to handle the lift that the cam has. Any flat tappet cam requires it's own dedicated lifters.
If you can spend a little more than I did you can get a marine roller cam and lifter setup. They have steeper ramp angles so the valves get open and closed quicker. That give you better cylinder filling and emptying, which means more power.
I was surprised when I noticed that I use less fuel when I cruise. I'm certain from my seat of pants test that the engine really has more power, it takes off really well. I don't hammer it off the line too often, only if my kid wants to ski, and I even roll it on then. But when I give the throttle stick a shove it does scoot.

I'm not a pro motor person so I used the kit setup from Comp. But you could also check what they recommend and build something similar from parts you pick, I think if I was starting over and the cost was not too much I'd look into their beehive or conical valve springs and see if they are doing any of their cool 4 pattern cams for marine use. The 4 pattern cams use different valve timing on the cylinders close to the center versus the ones on the ends. This an accommodation to the different lengths intake runners. They also offer hardened surfaces in their cams for a fee. it's called nitriding, and it's supposed to slow down wear.

 

[Greg68S]

Best plan I've seen yet... The 2516 (http://www.edelbrock.com/automotive/mc/manifolds/marine.shtml) intake will accept both square and spreadbore carbs.

I can say from experience. This intake manifold is awesome. I was very happy with mine. I ran a mild cam, vortec heads, a flat top piston, and the 2516 edlebrock in my 1989 Thompson. Dyno'd the motor at my local speed shop. 315hp at the flywheel! Big jump for that '25 cuddy that only had 260hp 5.7. I paired it with a reman alpha one and she preformed nicely. Knowing what I know now I'm thankful I didn't blow up that alpha but I was young a dumb so to speak and that was my first boat. I didn't own it long after that. I upgraded to a small pocket style cruiser. I needed more room. Looking back now I should have stroked it and paired it with a bravo. A SS24P prop would have been awesome!!!!

 

[Walt T]

Cam I have in my stroker, requires Vortec head modification

Camshaft Part Number:CCA-08-417-8

UPC:036584038405
Cam Style:Hydraulic roller tappet
Basic Operating RPM Range:1,200-5,200
Intake Duration at 050 inch Lift:218
Exhaust Duration at 050 inch Lift:224
Duration at 050 inch Lift:218 int./224 exh.
Advertised Intake Duration:270
Advertised Exhaust Duration:276
Advertised Duration:270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.495 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.503 in.
Valve Lift with Factory Rocker Arm Ratio:0.495 int./0.503 exh.
Lobe Separation (degrees):112
Computer-Controlled Compatible:No
Grind Number:CS XM 270HR-12
Valve Springs Required:Yes

 

[Scott Danforth]

I updated to vortec heads, switched to a vortec marine intake (factory Volvo Penta part). I added a carb spacer for low end torque. Added the Comp Cams 262/268 cam and roller rockers. added a Melling high volume oil pump.

Engine went from 9.4:1 to about 10.3. Talking to the local engine shop, its estimated we bumped from 275hp stock to about 330-340 range.

my thread is here http://forums.iboats.com/forum/engi...ormance-upgrades-for-an-aq271c/page3?t=503800