[All4Fun]

I am currently porting the heads for my engine. (To cheap to pay to have it done and want to learn something at the same time.LOL) They are 1970 #13 large valve heads. I have already matched the ports to the intake gasket(Felpro) and blended them out an 1"-1 1/2" into the runners. Bowl work is done with the short side radius blended in smoothly to the valve throat. All sharp edges,ridges(casting shift)removed and blended. Valve guide bosses have also been radiused. I know the exhaust side should be near mirror finish to avoid carbon build up. Due to the severe casting imperfections on the intake side I went ahead and did the whole port. My question is what kind of finish (grit) do I put on the intake ports/bowls in order to maintain adequate fuel dispersion/atomization? I know this is pretty important. They feel and look great but I want to be sure. (Street Use). Please anyone able to assist I would be appreciative.

Thanks,
John

[All4Fun]

I am currently porting the heads for my engine. (To cheap to pay to have it done and want to learn something at the same time.LOL) They are 1970 #13 large valve heads. I have already matched the ports to the intake gasket(Felpro) and blended them out an 1"-1 1/2" into the runners. Bowl work is done with the short side radius blended in smoothly to the valve throat. All sharp edges,ridges(casting shift)removed and blended. Valve guide bosses have also been radiused. I know the exhaust side should be near mirror finish to avoid carbon build up. Due to the severe casting imperfections on the intake side I went ahead and did the whole port. My question is what kind of finish (grit) do I put on the intake ports/bowls in order to maintain adequate fuel dispersion/atomization? I know this is pretty important. They feel and look great but I want to be sure. (Street Use). Please anyone able to assist I would be appreciative.

Thanks,
John

[T Hutchinson]

Hey John, not suprised you havent got a response yet, I dont think there are too many do-it-yourself porters on this sight. After all the trial and error I had to go through to get D ports to flow a measly 280 I can see why. I've never polished the exhausts to the level your speaking of but you might want to try the video by Pete McCarthy on head porting offered in PE magazine, if you dont alrady have it. I havent seen it, but Pete helped me when I was struggling with technique and I can tell you the guy knows his way around a port, and one hell of a nice guy to boot. Good luck!

[Will]

The shape of the port is far more important than the finish on it. In the intake port you want a rough finish to help keep fuel from dropping out of suspension in the "boundary layer" but how rough of a finish is hard to say. In short, I think you'd have to REALLY work to get a finish that's too rough, so just use a sanding mandrel or coarse stone and go over the surfaces in the intake that you worked on. If it looks like a sanded finish, it's probably rough enough. On the exhaust side, polish to as close to a mirror finish as you can since there are no worries about liquid fuel falling out of suspension. I ported the #13s on my 400 myself and it was a lot of work. I used the guidelines given in the HO Racing "Engine Design and Blueprint Assembly Manual" to do most of the work but because I didn't understand what they wanted me to do on the port floor as it transitions to the short turn I left that area alone. I now know that what you need to do is level the port floor, making it flat. Do NOT lower the port floor, just "square off" the transitions to the port walls at either side of the floor. Frankly, it was a lot of work and without a flowbench I have no idea whether it made any difference or not (though I suspect it did). Thus my decision to spend the money and let a pro do my new heads this time around. Good luck and be sure to let us know how your new engine runs!

[PONTIAC DUDE]

#80 grit. Later. http://PontiacPower.cc

[All4Fun]

Thanks alot guys for the help. As always it is much appreciated! As for the finish, I have it at 80 grit... it just looks so smooth compared to what it looked like before, I wasn't sure. Man was there alot of casting crap in those intakes. The exhaust was even worse. Even without altering the ports just cleaning them up has got to make a diference in flow. Should be plenty sufficient for my flow needs. (068 cammed 400 w/1.60 ratios).

Thanks Again All!

[Triggerman]

If you are looking at a certain area of the port and are in doubt as to whether material removal would help....don't remove any material. You'll almost always be right. The money you saved on paying for porting can be used to flow the heads when you are done. Flow all 8 ports. This will identify whether they all flow within an acceptable margin of each other or not. Don't be surprised if they do not. If they don't, you will get different plug readings across the 8 cyinders and you will be blaming the intake for not distributing properly. The intake won't know what you are talking about. TM
Also, I see you talk about "radiusing the valve guide" area. Be very careful in this area. The guide support area has 2 important jobs to do. It must support the valve to keep it from wandering around and has to have contact material available to transfer all the heat off the valve back into the head casting, and thence to water passages. Removing material from this area reduces effectiveness of both these tasks. If the valve head is allowed to move around, it will harm the concentricity of the seat and it's seal. Reducing the valves ability to shed heat could result in more sensitivity to detonation. In addition, there is very little (if any) flow to be gained by cutting the support area down. I would limit work in this area to minor flash cleanup. TM

[This message has been edited by Triggerman (edited 07-01-2000).]

[All4Fun]

Thanks for the response Trig!

I limited my port work to removing casting imperfections that might impede flow. I am definitely not comfortable enough to alter the port in any way. I do have H-O s' books and have studied their blueprints but do not feel without access to a flow bench I could evenly alter the ports. As far as the valve guide bosses, all I did here is round off the edges slightly. I hope I didn't hurt anything here; there was minimal material removed.

[Triggerman]

Sounds like you are working at the proper level of modifications, considering that you don't have a bench to verify your results. You might get a copy of the series of articles Pete McCarthy wrote for HPP and maybe a copy of his porting video. Lots of good theory to absorb. TM