Offshoreonly.com - Cam suggestions for 383 build

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Quote:

Originally Posted by SB (Post 4083403)

AC Crooks - you are correct about the HP and that smaller (212/218) comp cams. I know you know your small blocks and that proves it. GMPP's 425HP motor uses better cylinder heads and 383 cid's and a larger 222/230 HR cam. As a note, Their Vortec single plane added 20hp over the highrise dual plane to get it to the 425.

also,edelbrock's catalog shows the hp/tq for their heads,cam and intake.plus he like to have his cams make some vacuum.

Could always install a $700 slob cam and ruin the party and get out of boating.

I don't think that a good recipe was copied and resulted in near identical numbers. The motor in PHR had a bigger cam. I think the guy selling them just gave him a bill of goods regarding the dyno numbers. Those HP an Torque numbers are what I would expect from a 383 with the cam Sprink is using. I'm just saying hey look at this, to much of a coincidence.

Quote:

Originally Posted by dbkski (Post 4083310)

So what are you implying? That two nearly identical engines one built in 2006 and the other in 2012 can not yield the exact same results? :lolhit: :lolhit: :lolhit:

The details in this case do not point to shenanigans by sprink's builder.

Looks to me that a good recipe was copied. Where was the magazine engine built?

Quote:

Originally Posted by Trash (Post 4082987)

Your limiting factor is not the fact that it is a stock exhaust manifold, or worrying about reversion, but rather trying to exhaust out the outdrive. That is your choke point. The Lunati cam would likely work but not trying to push it out the prop. Keep the LSA wider as you go up in cam size and utilize thru-hull exhaust with the stock manifolds and risers. Crower has some nice hyd roller cams that would work too. Don't pick a cam that makes peak power at 6000 rpm as you will likely never see that in a boat. Some drives don't like that.

Target an LSA in the 112-114 degree range.

FWIW, I'm running a cam nearly equivalent to the 276XM, stock exhaust with thru-hull and no reversion.

A lot of useful information from all of you, thanks. Is your engine loud all the time? I'd love to hear the engine loud but not all the time. I'm pretty green on terminology but could I run a cam like the 276 comp and quiet the engine when wanted or is that getting into a lot of expense? I need to get this project done before my 12 and 14 year olds are grown. My old job is gone that let me spend what ever I wanted on toys and I'm tempted to buy a mild hyd roller just to get it done and get everyone out fishing and skiing. It just seems a shame as well built as the motor is.

Quote:

Originally Posted by lil red (Post 4083325)

Why is a custom ground cam out of the budget? I've had a couple done recently for less than I could get a comp from jegs.

I don't have the $300 or $400 I was quoted to go that route. The comp 270xm roller I can get for $259. Not sure about the 276 comp but it looks like if I were to go that route that I will have to sink more into an exhaust I had not counted on.

Quote:

Originally Posted by sprink58 (Post 4082928)

I built twin 355 Vortecs two years ago with the comp XM 264 Roller.Here are my results:

SuperFlow
Dynomometers and Flow Benches
SF-902S

355 MARINE CHEVROLET Result Summary Date 12-20-2012 1:46 PM Temp 80 Deg F. RH 74%

RPM TQ* HP*
2600 399 198
2800 408 218
3000 421 240
3200 430 262
3400 436 282
3600 440 302
3800 444 321
4000 448 341
4200 451 361
4400 450 377
4600 443 388
4800 438 401
5000 431 410
5200 421 416
5400 409 421
5600 396 422
5800 373 411
Max 452 422
Avg 426 339

* Test Exhaust 1.5" Diameter Dyno Tester Supplied Headers.

355-cid VORTEC SPECS

Bore / Stroke / CID: 4.030 / 3.48 / 355 cid
Compression: 9.4:1
Block: GM factory four-bolt 350 L-31 VORTEC
Crank: SCAT forged-steel PN 1101-11133
Pistons: Probe forged (PN 130212334-030)
Rods: Probe (PN 1201-10062) 5.7"
Rings: Total Seal Moly
Bearings: Clevite
Gaskets: Mr. Gasket and GMPP
Cam: COMP Cams (XM264HR) 212/218 at .050, .488/.495 lift, 110 LS
Lifters: COMP (PN 875-16)
Chain: COMP (PN 2100)
Pushrods: COMP (PN 7372-16)
Rockers: COMP 1.5:1 (PN 1417-16)
Heads: GMPP Vortec (Scoggin-Dickey PN SD8060A)
Manifold: Edelbrock Performer RPM Air Gap (PN 7516)
Carb: Demon (PN 1402010VE)
Distributor: Davis Unified Ignition DUI-7000
Spark Plugs: Autolite AR103
Oil System: Milodon HV (pan PN 31505)

I am running stock Mercruiser OEM Exhaust with y pipes in the boat so I'm loosing power on the top for sure. running 1.5 Ratio Bravo I's with 23" Mirage I have all the power and torque I can use. i have no reversion issues and make BIG TQ numbers down low.

Do you have flo sheet on those heads? I'd like to compare to the 180cc EQ performance heads I went with. When you say y pipes are you saying tru hull or out the prop? I almost went with vortec heads then decided on the EQ 180cc with 64cc intake runners. They used molds of ported ports on these heads. The intake to exhaust flow ratio is real good on these heads and should make excellent torque . I bought the stroker crank on ebay for $270. It's a kellog forged and nitride treated crank. A guy in Oklahoma went to the auction at the Mercruiser plant when they shut down and bought about 30 brand new stroker cranks for scrap price then turned around and sold them on ebay. They were all big and small block chevy cranks still new in the boxes. He really had no idea what these cranks were worth. I should have bought 4 or 5 at that price.

I went with 5.85 Oliver connecting rods and RaceTec forged d dish pistons with valve reliefs for up to 570 lift cam. The deck was cut down with the pistons .005 in the hole.Compression comes out at 9.3.1.This is a link to the heads I bought except the ones in the link are a bigger version of what I have.http://www.ebay.com/itm/Cast-Iron-cy...056b0a&vxp=mtr

The EQ Heads are very good. Will make a little more power than stock Vortecs.

Quote:

Originally Posted by SB (Post 4083744)

The EQ Heads are very good. Will make a little more power than stock Vortecs.

I hope so. I've read a few articles on engine builds where they were used and made real good torque. I had talked to a well known head porter who was familiar with them and he encouraged me to go with them over EQ's vortec heads which are pretty good also. The EQ performance heads look very much like a ported Dart head right out of the box for a lot less money and are much thicker than some of GM's crack prone heads. They are a quality casting.

Quote:

Originally Posted by 38special (Post 4083514)

I'm tempted to buy a mild hyd roller just to get it done and get everyone out fishing and skiing. It just seems a shame as well built as the motor is.

FYI:
I did a top end on a high hour 350 Mag (260HP) in a 20ft boat (really 19ft) and about 2800lbs.
218/224 at .050" / 113LSA Comp Extreme EFI HR cam
180cc heads
Weiand Air Strike (like the Eddy Air Gap)
650 Vac BG Carb
Eddie Marine Exhaust Manifolds (already on boat)
Merc Alpha Outdrive

15mph increase was result. NO BS. I'm intimate with that boat. LOL.

It's also an animal planing if at WOT - so....that needs to be held back to take care of outdrive.

Reason why I mention above is that you have same size and near same weight boat + a bigger engine. Heads are pretty much the same performance wise.

So, even if you go a little smaller on cam, it should still be an animal compared to whatever was stock. Just remember what we said top rpm will be as far as best speed. That 212 at .050" cam from Comp will probably be 4600 rpm.

Quote:

Originally Posted by sprink58 (Post 4082928)

Interesting setup, it's similar to what I put together in some aspects.

Anyone care to guess what it will make? Below are specs;

Bore / Stroke / CID: 4.030 / 3.48 / 355 cid
Compression: 10.2:1
Block: GM factory four-bolt 350
Crank: GM Forged/Balanced
Pistons: SRP flat top
Rods: Eagle I-Beam 5.7"
Rings: JE
Bearings: Clevite
Gaskets: Cometic
Cam: Bullet Cams (CHS284/292HR112+4), DUR @ .050 230/238, .530/.530, LSA 112, INT C/L 108
Lifters: GM Dog Bone Roller
Chain: Cloyes Billet
Pushrods: Smith Bro's
Rockers: Pro Magnum 1.5:1
Heads: Edelbrock E-Tec 200
Manifold: Mercruiser HIgh Rise Dual-Plane with 2" spacer
Fuel: MEFI 1, 90mm Throttle Body
Distributor: Merc.
Oil System: Melling HV
Exhaust: Stainless Marine, long tails

http://youtu.be/9RlLV8QBbCk