I began porting the L98 heads on my Camaro, and I just wanted to make sure that I was doing everything right. I'd like to get my work examined by the experts...

Thus far, I have removed most of the casting marks within the intake and exhaust ports, polished the exhaust ports (as much as I can), smoothed out the bowls, and properly radiused the short side underneath the valve.

I don't have the luxury of a die grinder, so I'm tackling this project with a Dremel. I've been using a ~40-grit stone, and 60- and 120-grit sandpaper rolls.

We'll start with the intake ports. The before picture is above; the after is below. They don't look terribly different, but I removed the humps along the port (though they're still visible), and cleaned up some of the rough casting marks. I did not touch anything that I didn't have to.



I was able to clean up the exhaust ports quite a bit. After using the stone, I went over it with the sandpaper rolls. 120-grit is the smoothest that I can polish; does it really need to be mirror-smooth? Despite the rough-looking ports in the lower picture, the walls really are smooth.



Lastly, the bowls. The short side radius wasn't terribly sharp on these heads, but it still needed work. The edges are now perfectly smooth with no sharp areas; I did not alter the actual shape/contour of the bowl in any way around this area.




I did not smooth out the valve guide area. My main reason for not doing this relates to clearances with my Dremel -- it'd be a little tough to fit it in there AND ensure that I didn't nick anything important. In the second picture of the bowls, you'll see that I left some casting marks alone, for the same reason.

I don't think that I'm going to match the intake ports to the intake manifold. It would take entirely too long with a Dremel, and I'm not sure if I'd even notice any major gains.

This post is long, I know, and I appreciate your looking over it. Am I on the right track? Can I set this head aside and start on the other, or should I make some adjustments? For reference, these heads are to be installed on an L98 350 with TPI, a ZZ4 camshaft, and headers. I have already had the heads modified with screw-in studs, cut valve guides, and larger springs.

 

Not bad so far.

But what you've worked on isn't where the majority of the gains are.

Look in particular at the intake ports, right behind the valves.See how it looks like the intake port is just about a cave, and the factory just sort of ran a conical tool into it to make the seat? Take out that ridge right there, and smooth it all down, without enlarging the area behind the valve; only take off the ridge. Also, on the intake side, the highest flow area is along the top (roof) of the port, on either side of the guide, as the port makes its 90° bend along there; you want that area as streamlined and smooth as you can get it, again without removing any more metal than you have to. Imagine taking a garden hose and squirting a straight stream into the port (or even do it in reality), and picture where teh water is going to go and the path it will want to take. That's the places you want to clean up.

Don't lower the floor of either the intake or exhaust ports; don't really do much to it at all, other than removing irregularities, because there's litttle flow there.

Mainly, the bowls are where the payoff is. So those 3 funky protrusions near the intake guides need to go away, for example.

That ridge around the valve guide is another feature that could stand some work. Smooth that down, and round the corners of the guide and the casting around it. That irregularity will cause a great deal of turbulence.

You're doing good at not "hogging" them out; that's a typical novice mistake, is thinking that "bigger" must be "better". Work on shape, like you are doing, rather than size.

 

Thanks for expanding on the porting, RB83L69. I figured there had to be more to it than what I did .

In regard to the ridge behind the intake valve, are you referring to the area directly opposite the port inlet (i.e. short side)?

Secondly, you said to keep the roof of the intake ports as smooth as possible. When you say "smooth," do you mean void of all irregularities, or truly as smooth as possible (a la exhaust ports)? If it is the latter, will there still be enough turbulence in there to properly mix the intake charge?

Finally, is there any need to slightly radius the rough edge around the exhaust crossover in the two middle ports?