Attempting this 5.7 build again.

[christoner2002]

Started looking at building a 5.7 Vortec engine for my boat last year, but after asking here, I saw I was doing it wrong. So, trying again. Looking for a decent reliable build that will not have any issues, yet may make a little more power then it had originally. This is what I have, and what the boat/engine specs are currently,

1997 Larson 206 Sei bowrider, originally had a 5.7 without vortec heads, and a 2bbl intake, Alpha One Gen2, 1.62 ratio, and a 21pitch Stainless prop. I changed it to a 4bbl intake and a Edelbrock 1409 600cfm carb when I bought it. On a gps, it will run about 53-55 on a good day. Engine is at over 700 hours, and is showing some signs of being tired.

New engine I am building,
1997 350 block, bored .030, decked .015, line bored, new freeze plugs and new cam bearings. Forged steel crank, turned .010 on the mains and the rods, rods have been checked and all are good. Pistons are these

https://www.summitracing.com/parts/slp-h815dcp in a .030 overbore. They look like the stock ones that came in it. 1.55 compression height. +12cc dish After decking, pistons will be .020 in the cylinder

The bottom end will be balanced as well.

http://www.jegs.com/i/JEGS-Performance-Products/555/210044/10002/-1 these are the head gaskets I am looking at. they are .024 thickness

That will get me at .044 quench. I know these are not the ultimate pistons for the build, but they are what I have to work with.

The heads are standard Vortec 062 heads. I will be adding the Alex's parts valve springs to allow this to take a little more lift on the cam. I also scored a pair of Crane Cams full roller rockers for $50 that are self aligning, and a 1.5 ratio.

Where most of my questions are is in the cam choice. I will be running this with thru prop exhaust. The factory cam was around .431/.451 lift and was a roller. I will be using a roller cam again. I am looking at three cams, and wondering what you all think would be the best choice They are as follows

Brand:Crane Cams Manufacturer's Part Number:104224
Part Type:Camshafts
Product Line:Crane Hydraulic Roller Camshafts
Summit Racing Part Number:CRN-104224

UPC: 021174039245
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,000-5,500
Intake Duration at 050 inch Lift: 214
Exhaust Duration at 050 inch Lift: 220
Duration at 050 inch Lift: 214 int./220 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 276
Advertised Duration: 270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.452 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.465 in.
Valve Lift with Factory Rocker Arm Ratio: 0.452 int./0.465 exh.
Lobe Separation (degrees): 112
This seems to be a mild a somewhat mild cam, that is similar to what was used in the older 6.2 Mercruiser engines.




Brand:COMP Cams
Manufacturer's Part Number:08-416-8
Part Type:Camshafts
Product Line:COMP Cams Xtreme Marine Camshafts
Summit Racing Part Number:CCA-08-416-8

UPC: 036584038382
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,000-5,000
Intake Duration at 050 inch Lift: 212
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 212 int./218 exh.
Advertised Intake Duration: 264
Advertised Exhaust Duration: 270
Advertised Duration: 264 int./270 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.495 in.
Valve Lift with Factory Rocker Arm Ratio: 0.488 int./0.495 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
Grind Number: CS XM 264HR-12
Valve Springs Required: Yes
This one is one of comp cams smaller marine hydraulic roller cams.



Brand:Chevrolet Performance
Manufacturer's Part Number:24502586
Part Type:Camshafts
Product Line:Chevrolet Performance LT4 Hot Cam Hydraulic Roller Camshafts
Summit Racing Part Number:NAL-24502586

Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,800-5,800
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 228
Duration at 050 inch Lift: 218 int./228 exh.
Advertised Intake Duration: 279
Advertised Exhaust Duration: 287
Advertised Duration: 279 int./287 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Valve Lift with Factory Rocker Arm Ratio: 0.492 int./0.492 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
Valve Springs Required: Yes
This is the LT4 Hot Cam from GM. Have heard of many using this cam, but not sure about reversion.

My Intake will be a Edelbrock 7516 RPM Air Gap for Vortec heads.

I will be reusing the Mercury distributor

Goal is to get 300-325hp to the prop. Does this seem like a decent combo? Also, anyone know if full roller rockers will fit under stock centerbolt valve covers?

Thanks for any help.

 

[Bondo]

but after asking here, I saw I was doing it wrong.

Ayuh,.... So far, I think yer still goin' the Wrong way,....

Ya don't need forged pistons, a total waste of money,...
Go with hyperutectic, with a D-dish, to match the Vortec combustion chamber,...

Ya Don't want a steel shim head gasket,... they rust,...
Deck the block to 0.000", 'n use a multi-layer SSteel head gasket,... their usually 'bout .043" or so,...

Is this the motor outa the boat,..??
Or another '97 ya found somewhere,..??

 

[alldodge]

Could give your self more metal and deck to 0.010, then get pistons with a + 0.010 and the .043 gasket

 

[christoner2002]

"Ya don't need forged pistons, a total waste of money,..."

The pistons are not Forged. They are Hypereutectic. Pistons are bought, and already balanced in the rotating assembly
I will see about zero decking it, and using a gasket around .040-.043

 

[Scott Danforth]

If the pistons have 4 valve clearances, its the wrong piston period.

They should look like this

 

[christoner2002]

Ok. I spoke to the engine builder, and he will take the pistons back as a trade. I will just pay a little more to rebalance the rotating assembly. Found a set of Keith Black pistons that have the d shaped dish.

https://www.summitracing.com/parts/uem-kb158-030/overview/

With that done, what cam do you think works best?

 

[Scott Danforth]

The cam will be dependant on your exhaust. With stock manifolds and risers, this is the biggest cam you can put in your SBC

http://www.compperformancegroupstor...e=CC&Product_Code=08-417-8&Category_Code=HRXM

Anything bigger and you need to go to aftermarket exhaust.

Since your building the motor, i would toss in a stroker crank as well (especially if you have to grind the crank or touch the rods)

 

[flipbro]

I would have your builder double check those pistons! Compression hieght is 1.678 on those KB. That's a 327 piston. You want compression hieght as close to 1.556 as possible not over. With what u had originally would have made 300 plus horse. Don't use a steel shim gasket.

 

[christoner2002]

Thank you for that catch Flipbro. I will call him in the morning.

 

[achris]

If you increase the valve lift, make sure you open the intake and exhaust ports in the head to take advantage of the extra lift. If you don't, it may have a negative effect on the output. If you intend using 'stock' vortec heads, use a cam with stock lift. And I'd use the cam that gives you the best LOW end torque. Boat engines want bottom end, not top end. (unless you plan racing, in which case, you're gunna need a bigger wallet! ) And if you make much more than 300hp, you're gunna need a Bravo behind it.

Chris...........