porting the SBC

I run in salt and that negates the possibility of using an aluminum intake. So Im stuck with regular marine stuff unless I go closed cooling, which I will not do.
5.7 GM Vortech
I have the Mercruiser bow tie high rise intake already installed along the the Mercruier / Weber version of the AFB carburetor.
Thunderbolt V ignition system.
Compression is right at 213 psi even, all 8 holes.
I figure that setup gets me to the 280 horsepower neighborhood.
It runs extremely well but i want a little more.

First thought was 202 heads and a cam. True that would put me up where i want to be in the 320 hp range but I would be lighter in the pocket by at least $1000. Paying and playing,, i know, I know.

Then I thought that just making what I have flow better might be a big improvement on its own.

So my thoughts are to pull the heads this winter and match port the intake manifold, exhaust manifolds and heads. I used to do that to my old Toyota 20R racing 4 bangers with great results 30 years ago.

My question is: do you thinks it's worth the hassle? Think I'll notice anything in performance? Or just a placebo effect from knowing its ported.

I haven't done it in 30 years, so has anything changed? Prussian blue, scribe to the gasket, remove material, polish casting bumps and pits from the passages is all I ever did.

Thanks.

John,From messing around with my Vortec heads and research on them light porting can be done (general clean up of the casting marks/lumps) but don’t take material away from around/behind the valve seats that is the main flow part (makes the vortex to flow so well) if you do it will flow less....then you need to go bigger valves to bring it back up, 400hp can be done easy on clean Vortec’s it’s the valve guide height that needs work easy done with a hand drill and cutters you can buy or run longer stems on the valves then a bigger lift cam.

Keep an eye out for Indmar Vortec intake they are ally but the water ways are bronze lined.   

Good luck with the build.      

I would have to agree for the most part on what Zach and Roger say. The Vortec heads flow really well right out of the box. Unless you can match up a port job with a new intake (at minimum), I would think that you're going to see very little, if any gain at all.
Now, if you had the old style non-Vortec heads, then it could be worth your time. From what I hear and read, you can expect 25HP gains.

I ported two sets of heads for my SBC (non-Vortec) but they were added with other mods at the same time so I can't really say what the porting itself did for it. The mods together were awesome and well worth it and I was really glad I did the porting.
Would I have pulled the heads, done just the porting and put it back together? Probably not. I had 50 hr's into the first set and 30-35 hrs. into the second set. Then you'll have to grind the valve seats before you bolt them back on because you WILL hit the seats once or twice. It's a given. Face it.
I must admit, it would be very interesting to do just once to see exactly what gains you can get. I would love to do just that to the GT40P heads in John's boat knowing how well that runs now. I would just have to get rid of about 100 other things I need to do first before the next hundred comes up.

If you go with a bigger lift cam you will need to use bee hive springs or open the old spring seats out to take stronger springs…also good to take out the old push in rocker posts and tap for screw in type …its all in my thread UK's 78 SN

John I'm at home on a tablet which I'm poor on look in maintenance page 30 and page 6 on my thread

At work now on a PC now Link UK's 78 SN

The downer with boats VS cars is you are limited to a smaller range of camshafts because if you get too wild with the overlap and duration you don't reap any of the benefits from the higher RPM operation (IE. unless you drop big dollars marine manifolds don't have the cylinder scavenging benefits of a collector style header).

I wouldn't be opposed to a closed loop system if I were a salty dawg either!

WFO:
4800 RPM / 49 mph and she flattens out bad around 4400.
I would like her to pull harder and higher. (did I just say that out loud?)

13 /13 OJ but it's an old OJ. Probably no better than the federal/.
You know Tim, I ned a prop anyway. maybe ill start there and leave a good running motor in one piece.

I just hot rodded the boys go kart and now everything MUST GO FASTER! Hah!

May be of interest too..Vortec marine intake