350 sb more power
 

ok let's see how im doing have twin 350 mags 1991 pushing 270hp. doing some research im looking at world heads s/r torquer 2.02 valves 2.020x1.600 the book says i will get another thirty hp im running emi exhaust w/stainleess risers.also changing to comp cam model#12-210-2 rpm 2200-5200 intake and exhaust @.050 is 218 valve lift .454.going to a new crank and rod kit with flat top pistons.does this sound like i will increase my hp if yes to approx how much.a friend of mine owns a machine shop im only paying for parts.also the engine will be balanced.? will i get reversion or am i safe.

For a boat you need torque. For torque the easiest way is CID. I would look at prepping 2 x 383 CID. These engine are capable of legit 400HP/475#/ft of torque and still be reliable. If you did this I would recommend going with sportman heads.

Chris

Stroke It Baby!!!
A 383 stroker kit is the way to go.
I built one for my single engine boat, and the difference is incredible! Tons of torque. I attached a breakdown of the parts I used. If you have any questions, just email me.

Paul :)

The attachment didn't work, so I just copied and pasted it here:

1. Chevy Four Bolt Main Truck Block Bored +.030”
2. Scat 383 Stroker Kit # 1-383IPS Consisting of:
· Scat 9000 series stroker crank
· Scat Forged 6” “I” Beam rods
· SRP Forged Dished Pistons +.030” # 138103 16cc Dish
3. Total Seal Gapless File-to-Fit Rings
4. Comp Cams Xtreme Marine cam # 12-236-3 (XM262-H)
5. Comp Cams Lifters # 812-16
6. Comp cams Valve Springs # 981-16
7. Comp Cams Magnum Roller Tip Rockers 1.5:1 #1417-16
8. Cloyes True Roller Timing Chain #
9. Clevite F-77 Tri-Metal Bearings (std.) Cam, Rod, Main
10. Melling High Pressure Oil Pump # M55A
11. GM Extended Oil Pickup for 5Qt. Pan.
12. GM Performance Parts Cyl. Heads #10125377
13. GM Performance Parts Intake Manifold #14097494

liberator thank you.how much for the parts no labor?

For a idea over the past 2 years I have ran two 383's and building another one.

1. 383

2 bolt block
eagle forged 3.75 crank
eagle h Beam "3D" 6.00" rods
SRP dished pistons. 9.9:1
vortec heads machined for screw in studs, guideplates
222/230 .542/.563 roller cam
All crane valvetrain
air gap intake
750 holley
EMI exhaust
around 400hp at 5200 rpm

last year I ran..

383

4 bolt block
same crank
same rods
JE flattops pistons ( 10.8:1) w/110 octane
AFR 210 aluminum heads 2.08/1.6 valves
234/242 .574/.595 roller cam
All crane valvetrain
Edelbrock victor jr intake port matched
750 holley
EMi exhaust
around 500 hp at 5500 rpm

now i am building this

383
same block
same crank
same rods
JE pistons ( 12.7:1) w/110 octane
same heads
250/258 .598/.598 lift solid roller cam
edelbrock victor jr intake port matched
800 or 850 holley
EMI exhaust
should be in the neighborhood of 570 hp

you don't even want to know how much this cost :eek: :D

im still wating for answer or comment on what i want.i appreiate information on the 383 but that's not what i want.

I have 1996 5.7s that were just rebuilt stock. I have built a few 383 stroker motors for cars in the past and would do the same but hate to tear apart or replace brand new rebuilds. I was thinking about just replacing cam, ignition, intake and exhast and then adding small B&M blowers. What are the pros and cons to that?

Re: 350 sb more power
 

Why new crank and rods? Do those motors have flattops already or are they dished? :)

Reversion... you see the cams I ran on my setups. i have never had reversion. With that small of cam you should not have any reversion, esspecially it is a little safer with the EMI exhaust you are runnin.

Are your exhaust thru the transom or thru the drive?

sonic28
The 12-210-2 cam you are looking at is a single pattern cam ground on 110* LSA. The Torquer heads have a good exhaust port with an I/E ratio of approx 78% but you would do better with a dual pattern with about a 4* split on a 112* LSA. The wider sep will provide some insurance against reversion. Depending on the displacement and compression ratio you go with(350/383) I can give you some duration numbers on shelf and custom marine grinds. Because your block is already set up for roller have you considered those options?
Bob

more compression or more cubic inches a 350 is still a 350 i'm going with 9.9 to1 vortec all stock with flat tops(i hope it does'nt ping)
i was told below 5000rpm think compression and use the biggest engine you can .
beyond 5000rpm it's all about the air flow
more cam without more compression =a dog.a lame gas suckin dog!that just sounds cool at the dock.you may make gains with magic camshafts and higher rpm's but watch your compression if you end up lower you will not gain a thing. i think you just might be able to make as much torque&hp as a stock 9.4to1 vortech but i'm not an expert i'm a dirty plumber
screw reversion

hmmmmm I know those 9:1/355inch single carb Nascar Busch motors make some big power, admittidantly with some big rpm however..........doug

Changing cranks and rods won't get more HP. If I understand you correctly and you want to stay with 350 CID. Then punch the engine to .030" Put a fresh set of flattops in the engine. I would run the Dart Iron 180's. Little better head then the SR's. Get a set of Edelebrock Air gap intakes. Run 1.6 rockers on the intake side and 1.5's on the exhaust. It is all about moving air in quick to make power. Induction system.

Save your money and use the rods and cranks in the engines. Just have them reconditioned.

Chris

chris if i go your way how much hp?
and thanks to all you others for reasponding.
paul

travis im going with flat top

Re: 350 sb more power
 

You should call Eddie Marine and tell them what you have told us. Based on the length of your risers and cam specs they should haven't any problem letting you know if you are safe or not. I would have thought that Eddie Marine would have questioned you on your cam specs and told you what to go with when you purchased them...If they didn't they should have. I am running the XM270 cam from comp cams and Stainless Marine manifolds and risers. I have no problem at all.

BH

I'm running 355'' with flat top L-82 pistons, 9.3:1, World SR 1.94/1.60 heads, Crane roller rockers, Speed Pro 460 lift/ 222intake 220 exhaust duration/ 112*lsa cam.
Had some efi problems with one but the one that was running well ran 5500 rpm with no complants. they started and idled well on 89 octane. I've done the cubes and compression route on the street..... which is way I don't want to do it on the water. Don't get me wrong if I were building a boat for a lake or short hops to the local watering hole, I'd go the with the set up Travis is running, BTW Travis have you seen the 450" Small Blocks yet?
One more thing the engine builder who is doing mine, built the same engine for his kid , less the roller rockers, and made 330 horse and 400 ft/lbs. on the dyno

ohh yeah.. I have seen them.. It just takes money.. and I don't have it LOL! :D :D

I'll have to go through my receipts to see what everything cost me. It wasn't too bad. If you're going to go with flattops, make sure you know what you're compression is going to be. 12:1 is cool, but where are you going to get the gas to run it? With 16cc dished pistons, 64cc heads, and .020" gaskets, I calculated my compression at 9.6:1. That works fine with 89 octane gas.

Paul, with what I have suggested should be a legit 70HP increase and 100#/ft of torque with max rpm set around 52 to 5400. . . useable power. Key is to get a matched camshaft to the head flow. I also recommend not buying assembled heads from the factory and just bolting them on. Nothing wrong with the work but as with any mass produced item, some attention to detail gets lost. Any good shop can disassemble and put a good valve job and mild blend work to pick up some easy power.

if you have any other questions you can e-mail me. .
[email protected]


Chris
Stef's Performance Oil Pan and Fabrication

thank you chris you came out with the information and answers i was looking for. and thank you all others for your response.
paul

I have been playing with different options for over 10 years on my 350. It started as a 300hp/5200rpm. Many mods and lots of money to around 370hp. All of my speed gains were from hull, drive and prop and weight mods. I think I gained 4-5mph on all the engine mods If I did not change anything else.

Changed to a 406 shortblock and that alone was the biggest jump in accelleration and top speed.

If you are going to change the rods, pistons and crank, got for the 383 rotating assy and decent cam. You will then have a good base from which to grow.

You can upgrade everything else slowly and not have to pull the engine.

Torque is the key

Kent
18 Donzi Classic 438hp/497lbs torque
"Mala"

there is a twin sbc buildup in my future.Id like to make 360 to 400hp. I too am concerned about long term reliability, not just blasts across the lake and back. Im talking Poker runs where your at near top rpm for 20 to 30 solid minutes at a time and 2.5 to 3 hrs for the day. has anyone ran a 383 or 406 in this type of environment?? I know the 350 may be short on displacement but theres lots of meat in the block and they can handle this type of use, Ive done it........doug

Travis I do believe that you are on the conservative side on your hp #s. :D Dwight

basic logic ,if GM parameters are9.4to1with89octane,30deg.adv.timing&4800rpm@WOT then the perfectly logical nut would go a little beyond knowing full well GM is not going to even come close to pushing the envelope as durabillty/warranty constraints dictate.
"torque is the key"(Kent)granted the relatively low(compared to a bush nascar,twin29)RPM a hotrod boat engine goes
you can find sonicsss'caveman engine in dennis moores'book(mercruiser280TRS)and see what he siad about it
high tech,high compression tolerent,efficient ,heart shape combustion chambers(like vortec)and roller cams are the way to go.GM made their 300HO into a 330HO
just by switching to vortec heads(same compression and valves with better combustion)the ram jet 350 is rated@350hp which is a(marine vortec)with a tunnel-ram-like EFI setup and headers
like you paul i'm from massachusetts and i only saw 89 octane fuel once or twice 92-93 is all i can get locally, why risk it any way.
i am looking for more torque between 4000and5200rpm wishfully hoping to turn the same prop faster, and you?

Don't want to hi-jack this thread, but I have a ? for Liberator21. You and I have the same 383, but I used the stock merc heads (but 2.02/1.6 valves, planed to 74cc, 9.7:1). My ? is about the melling 55A pump (Z-28 hi-volume). What are your pressures at idle , 2000, 3000?

At idle, I'm 50-60 at idle and can reach 80 at 2500. What about you. Seems high.

oh ,ya !my point is,i think your combo is good but a little old shool and if you are going to go through all the trouble?...and if any way possible GET SOME BIG BLOCKS
and stop kidding yourself

Here is a link to what my 355's are.............I spin them 6000 all day long...........I also do the poker run thing. I ran them for 400 hrs before a freshen up.

Also, don't let anyone scare you away from solid roller cams. Set up right they idle awesome & make some awesome power.

If you have any questions, feel free to PM me.

http://www.offshoreonly.com/forums/s...ghlight=Crower Canfield&pagenumber=2

RJ

ya seems high you'll wear out your distributor/oil too heavy?

Oh yeah, you'll have to go to the second page where I list the engine specs

Large CID small blocks will live at 5000 to 6000 rpm no problem, the key is the tolerances need to be dead on, machine work has to be top notch, and you have to use quality parts. Just had a customer tear down a 417 CID circle engine and it had 4000 laps on it at 7400 max rpm. Engine is well maintained, good parts.

Vortec's are extremely good heads, very good power as we use them in limited carb classes quite a bit. Negtive is they have had a history of cracking and due to the runner volume they are not suffiecent to supply larger CID engines with adequate airflow unless you get cam crazy and that is not a good idea with a boat.
You need to match the parts to the desired powerband to achieve what you want.

That oil pressure is way to high. For a NA engine in the marine world with HP under 400, a std oil pump is fine. We do recommend a heavier spring for marine application.

Torque is key and the easiest way to get more speed out of a boat is CID gained with stroke. But I must say a pair of 434 CID SBC would be strong power plants and a weight savings.

Chris

:D

If you are going 383 you can step up to the Comp Cams XM 278 and still have plenty of low-end torque. It sounds nice too.

Roby

Nothin but a solid roller in whatever you choose !

:D