Porting stock 351w heads... getting started

[SadbutTrue]

i was told the best way to go about this was to buy a certain gasket and use it to draw an outline of how much of the ports you want to take off (both intake and exhaust)... first question is what gasket should I use, and how close do I make my cuts to its lines.

Second question, is what tool should I use?

Also, is it really worthwhile to port the headers at all?

Ben

 

[LMan]

http://www.sa-motorsports.com/diyport.htm

 

[allcarfan]

I would mildly port the headers if there are some rough spots, but be careful because there isnt a lot of meat there.

If your heads are cast iron, id get a nice stone to be used in a die grinder. You can use a dremel, but it takes forever. You could buy some Carbide porting bits on ebay to help you along, but be forwarned...they are VERY aggressive when used for porting.

I suggest a felpro 1250 gasket for your intake ports. You can go with a 1262, but thats a BIG MOFO. Like you said, trace the gasket around the ports. I port all the way to the lines on a 1250 gasket. I start with each of the corners in the port, and then the top and bottom and sides to match. BE CAREFUL!!! DO NOT BREAK INTO A WATER JACKET>>>>DO NOT BREAK INTO A PUSHROD HOLE!!! You can see how much you are taking off, but look at all of the metal residue to see how much you have really taken off...dont over do it.

For the exhaust ports, I like to use this gasket made by...I think either Earl's or Mr, Gasket. it is a metal gasket with graphite inserts for the ports. The ports are pretty big when you buy this gasket. its pricey though..I think about $40/pair...but they are reuseable and you can actually port the inserts if you want!

As for bowl work.....i cant help you much there....just smooth all of the jagged edges and be sure not to over do it. Make sure the heads are disassembled too. DO NOT port the combustion chamber. If you do, you will make it bigger and lose compression. Plus, you could mess up the valve seats.

any other help?...just post up.

 

[brianj5600]

I am a fan of streamlining the bump in the exhaust, rather than removing it completly. Leaving a tapered shape behind the valve will smooth air flow. On the intake entry, keep it conservative. Opening the entry more than needed will create a bulge in the middle of the intake tract. I have seen people use too big of a gasket and slow velocity in that area, only to speed it back up closer to the valve. I use an electric die grinder since I don't have a compressor to keep up.

 

[allcarfan]

I think someone needs to post a picture of a head with arrows pointing to all of these areas that have been mentioned so a novice knows what is being talked about.

On the intake side, you want to use an 80grit sandroll, nothing finer. You want to keep it rough for better fuel/air atomization. Do the same on your ports on your intake. ON your exhaust ports, you want them as SMOOOOOOOOTH as possibly...even polished if you can do that!

This will make the air turbulent entering your head...mixing up the air and fuel...and it should slide/shoot out of the exhaust port!

 

[SadbutTrue]

yeah, if anyone could give me a little more direction on what to do with the bump, it'd be appreciated. When you say "Streamline" could you give me an idea of what shape I should be shooting for? It seems easier to just remove it completely. And if anyone could post on "signs" I should look for to know I'm about to bust into a pushrod hole or water jacket, or simply good rules of thumb to avoid them, I'd appreciate it.

The heads are 69' heads, btw.

 

[brianj5600]

Looking from the combustion chamber, the bump should not be touched next to the guide. Picture a line from starting on each side of the valve, on top of the bump, that connects to where the bump rejoins the port roof towards the exhaust flange. Draw another line from the back side of the valve, on top of the bump, to the same point. It will look almost like the head rest that tapers back onto the trunk of an old racing sports car from the '60s. My AFR's have a similar shape behind the ex valve. Clear as mud?