383 Stroker
 

Hi:
I'm a new member, I just found this site today, and found some useful tech for myself. I might be able to give you some insight to what you are doing. I just finished building a 383 stroker for my 21 foot Fourwinns Liberator. I used the Scat 383 stroker kit which included a 9000 series cast crank (Forged is an option), SRP forged pistons (Dished), and Scat forged rods. I used stock Chevy late model center bolt valve cover heads with 64cc chambers. The heads were pocket ported, gasket matched, and the valves were given a 30 degree back cut for improved partial lift flow. This along with the pistons .025" below the deck and sierra marine head gaskets (.020" uncompressed) gives me a calculated CR of about 9.6 - 9.7:1. For the cam, I used the Comp cams Extreme Marine Part# 12-236-3. Advertised duration: 262 intake, 268 exhaust, with .462" intake lift and .477" exhaust. This is a flat tappet cam, and yes I know, I should have gone roller. I also used the matching springs, and roller tip rockers (1.5:1). For piston rings I used Total Seal gapless. A friend who races semi pro swears by them. For the intake I'm using the GM performance parts Hi Rise Z28 style cast iron with a Quadrajet, and for exhaust, GLM center rise cast iron with through hull exhaust (Engine is salt water cooled). This engine runs like a dream! Idle is nice, not lumpy, but you know something is there. There is so much torque, that the boat pops up on plane like it weighs half of what it did with the old engine! Top speed went from 49mph (Radar), to 60!! That was with stepping the prop up to a 21" pitch from a 19". The engine has 10 hours on it as of winter lay up, and when the spring comes I'll have to finish dialing it in. I'm having some carb issues, so I'm building a totally recalibrated carb for it. I run it all day on 89 pump gas with 12 degrees inital advance. I don't remember what total advance is, but I know it's allot. I've run it on 87 with no problems. I hope all this info helps. if you need any more, just let me know.

Paul

Paul, you have a fantastic engine that seems like it is matched perfectly. Too many people go for that overkill cam just for the sound and wonder why it won't perform like it sounds.

Anytime you can have this much torque and top speed on a bowrider you're on the right track

Roby

Thanks, But the Liberator is not a bow rider. This was Fourwinns top line performance cuddy back in the 80's and early 90's. I remember seeing them at the NY boat show in the 80's, and always wanting one. I finally bought this one 5 years ago for a song needing an engine. I put a 280 HP 350 in it, but last year I said That's Enough! I WANT MORE SPEED!! (Like any fine american!). So I built the 383 last winter. When I save a few more bucks, I want to get a set of stainless headers. Know anyone with a set of headers for a small block... cheap??

Paul

Sorry about that, I didn't realize it wasn't a bowrider.

Roby

I ran a few different roller cams in my 383.

First setup
vortec heads
air gap intake
750 holley
9.8:1
crane roller 222/230 .543/.563 lift on a 112 LSA
EMI exhaust
max hp around 5250 rpm, 400-415 hp
took boat from 58mph to 70.1 mph

Second setup
AFR 210 heads
Victor jr intake
750 holley
10.8:1
EMI exhaust
Crane roller 234/242 .574/.595 lift on a 112 LSA
Max hp around 5500 rpm, around 490-500hp
took boat from 70.1 to 75.3 mph

What i am doing now.
AFR 210 heads
Victor jr intake
800 holley
12.6:1
EMI exhaust
crane solid roller. 250/258 .598/.598 lift on a 112 LSA
max hp around 6000, probably around 550-570 hp Plan on spinning it up to 6500 rpm.
Hoping for 80 mph with this setup but probably gonna fall short.

Paul, thanks for taking the time. Those are some impressive numbers, especially given that you don't seem to have changed to high performance heads or roller cam just yet.

Traviss, given your experience, do you have a recommendation for a specific roller cam to be used with the AFR 195 street heads, with dished forged pistons, to run on 87 octane?

ttt