Those specs with the long exhaust duration is mainly suited for N20 applications. It would work decent on a 383 SBC but it all depends on the cylinder head flow and exhaust system. An aftermarket head with a good exhaust port and I/E flow ratio would not need that 12* split between I/E to make good power.

For ex... My AFR heads have a very good I/E ratio and the best power is usually made with cams with only 1-2* favoring the exhaust. Ex 224/226. Except in a marine application our manifolds don't flow as well as long tube headers and a little more exhaust duration is needed.

I have a question since were on the subject of a 383 conversion. How much can you get out of a 350 block? Is 383 the most you can get without honing anything?

Yes I used them out of the box with the Crane, When I went to the Bullet Cam we installed bronze guide liners and Isky valve springs. Out of the box they used oil. No detonation with 93oct. I was more than happy with the Bullet cam picking up 4 mph with a cam change is very good. This set up worked for me and our 272 Formula.

You got to bore it .030 to get 383

Without boring the block you could build a 380ci with a 3.750" stroke crank and 4.000" bore.

You can take a 350 block out to 396ci using a .030" bore and a 3.875" stroke. That's about the biggest I would want to go.
A few have stuffed a 4.000" stroke crank in to get over 400ci but it does not leave much compression height on the pistons for a marine application.

dont do all that work to the engine then leave stock exhaust even if you have to go through the prop.......I switched to polished Revolution Marines and on bone stock 350 carb engines and saw immeadiate noticeable torque increase right out of the hole and another 500 or so rpm on top.....they are a direct replacement for stock.......plus I took 100 lbs a side off the back of the boat, 200 lbs total!!.......I would think you would see even more gains on your hopped up engine.......doug

That's good - I think I'm going to stick with a flat tappet cam as the retrofit roller stuff is pricy and this really isn't an all-out performance boat hull anyhow... Interesting info on the oil consumption - I've had a couple sets of the sportsman II's on IMCA style modifieds and haven't had them use oil...

I'm thinking I'll swap exhaust manifolds later - gotta keep some sort of budget here if I want to stay out of the doghouse....


Next question is on oil pan... I'm thinking about running a 'diamond stripper' screen style windage tray and getting one of those cheap "drag" style 7-quart pan and pickup combos - figuring the extra capacity should help keep oil temps down a little and the windage screen to keep the oil in the pan - Oil pump will probably be a melling M55HV and a matching steel sleeved shaft. anyone have a better "budget" oiling setup without going dry-sump OR is this overkill and I should just run the stock pan setup?

I've always used a 7qt kickout Moroso oil pan with the stock GM windage setup and a Melling M55A high output oil pump. On my 355 solid roller that spun 6500rpms I did opt for M55HV. If your staying under 6000rpms I don't see any need for the HV pump. It takes more power to turn it for no real return. Add the larger pan and get as much windage as you can. A regular or M55A HO pump should do you fine.

On my new 385ci build i'm using a Hamburger 7qt marine pan with built in windage tray and a blueprinted M55A HO pump.

I used Milodon 7qt part # Mil-30902 $169.95 and MEL-M55HV pump. We also ran a 454Mag oil powersteering cooler and amsoil 20/50 series 2000, After a hard run oil temp only 210deg.