350 build

[mtnrat]

I am slowly collecting parts for my 350. I am looking at the new vortec bowtie heads.
Vortec Bow-Tie has all-new ports that are taller and narrower, the idea being to increase velocity while maintaining volume. The heads are available in "small-port" (PN# 25534421) or "large-port" (PN# 25534431) versions, with the small-port heads boasting 185cc intake runners and 65cc exhaust ports; and the large-port heads cast with 215cc intake ports and 84cc exhaust ports.
Out of the box, the heads come with 66cc combustion chambers and 0.450-inch deck surface thickness. GMPP tells us a camshaft with up to 0.530-inch lift will work with the heads, too. Assembled heads come with 2.00/1.55 valves, too. Additional details include mounting provisions for early-style valve covers or the later-style center bolt covers, as well as mounting holes for earlier six-bolt intake manifolds and later-style four-bolt Vortec manifolds.
I am going to roller retrofit and use quench pistons(about 9 to 1 compression). I got a set of HP exhaust manifolds and risers from Dennis Moore Performance(ebay).
These heads look promising.
What do you all think?
Cheers.

[Ryan00TJ]

I am also building a 355 and retrofitting to a roller cam. Stick with the small 185cc port for 350ci. The larger port version is a little much for 350 cubic inches. Bang for the buck they are a nice jump over the older stock heads.
What are the rest of the engine specs? Decided on a cam yet?

[mtnrat]

The small port is the one I am looking at. The cam I am considering is the XM264HR from comp cams or something very similar. I have a marine 350 with only 30 hours, but it is currently set up for very low hp.
I am going to change the pistons(quench style 18cc dish depending on measurements I get when I take apart the existing engine), retro roller it, put on the bow tie vortec heads and use the HP exhaust manifolds from Dennis Moore. I will also use a vortec intake and a Qjet carb.
Should scoot my boat pretty well. Do not want too much cam as I use the boat for a lot of pulling as well as just cruising, but I still want top end.

[Ryan00TJ]

The small port is the one I am looking at. The cam I am considering is the XM264HR from comp cams or something very similar. I have a marine 350 with only 30 hours, but it is currently set up for very low hp.
I am going to change the pistons(quench style 18cc dish depending on measurements I get when I take apart the existing engine), retro roller it, put on the bow tie vortec heads and use the HP exhaust manifolds from Dennis Moore. I will also use a vortec intake and a Qjet carb.
Should scoot my boat pretty well. Do not want too much cam as I use the boat for a lot of pulling as well as just cruising, but I still want top end.
Should make a nice well rounded setup. The XM264HR cam should be quite civil in docking and provide a broad powerband. The way I look at it, you won't be disappointed going to a roller setup over the flat tappet. You have addressed all areas, intake, exhaust, etc. Combo is everything. I would recommend staying away from hyperutetic pistons and go for a set of forged if you have the cash. I found out the hard way they won't last in a hard run marine application.

[mtnrat]

Thanks for the heads up on the pistons. Who makes or supplies suitable forged quench(d-dish or reverse dome pistons). I may want to get a balanced rotating assembly.
Thanks