Blog Title: dsm-onster
I'm bored and I have a minigrinder. Hmmm. . . . Head porting!!!
Waiting out the Nor-Easter here on the Eastern Shore, VA. Can't work. So I started porting my head. This head is a 1g head off an n/t block.
I read the nice little write up here about mild porting your 1g head. Great stuff. I can see how there would be a gain. The valve bowls are hardly conducive to smooth flow. There's imperfections, lips, and other stuff going on right where the port turns into the valve opening. There are many casting imperfections.
Also, specifically for the short side radius of the exhaust ports, there's a nasty almost ripple series of rises. . . at least on this particular head. This took ALOT of "touch" to remove, because I didn't want to alter the shape of the port. There was no ripple in short side radius of the intake port, however.
I should have taken a shot of the exhaust ports before doing this work. But here's the finished product on that side at least.
I will start the intake side soon. Here's a few shots of the imperfections. Here's where the gains probably will be the most, because the lip is a direct step down in diameter, as the exhaust lip is a step up in diameter:
Here's an example of some weird shapes in the intake port. There was this kind of stuff in the exhaust port, too:
Here you can see that nasty ridge at the intake port bowl. I'll bet the airflow here at mid valve-lift is like
! Also this was at the exhaust port, but the exhaust gases are not as affected by this because this becomes a step out.:
Nevertheless, a smooth transition is still better. So they got ported there too. None of this was about reshaping the ports, just cleaning them up. I will still need to go into the exhaust manifold side of the ports and clean up the casting imperfections.
I read the nice little write up here about mild porting your 1g head. Great stuff. I can see how there would be a gain. The valve bowls are hardly conducive to smooth flow. There's imperfections, lips, and other stuff going on right where the port turns into the valve opening. There are many casting imperfections.
Also, specifically for the short side radius of the exhaust ports, there's a nasty almost ripple series of rises. . . at least on this particular head. This took ALOT of "touch" to remove, because I didn't want to alter the shape of the port. There was no ripple in short side radius of the intake port, however.
I should have taken a shot of the exhaust ports before doing this work. But here's the finished product on that side at least.
I will start the intake side soon. Here's a few shots of the imperfections. Here's where the gains probably will be the most, because the lip is a direct step down in diameter, as the exhaust lip is a step up in diameter:
Here's an example of some weird shapes in the intake port. There was this kind of stuff in the exhaust port, too:
Here you can see that nasty ridge at the intake port bowl. I'll bet the airflow here at mid valve-lift is like
! Also this was at the exhaust port, but the exhaust gases are not as affected by this because this becomes a step out.:Nevertheless, a smooth transition is still better. So they got ported there too. None of this was about reshaping the ports, just cleaning them up. I will still need to go into the exhaust manifold side of the ports and clean up the casting imperfections.
Total Comments 2
Comments
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And NO!!! that is NOT a pube in that last picture!!!!!
Posted 09-26-2008 at 06:29 AM by dsm-onster
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Rough Inned the portmatching on the Exhaust side.
I opened up the exhaust ports to match the exhaust manifold ports. There was ALOT of material to remove. Blending it in took me quite a ways into the head runners.
Left ported. Right unpored.
There are "humps" a the outer wall of the port pairs close to the floor and right at the turn (short side radius). I smoothed them out as well. Here's my thread about these, Porting head: What to do about the "humps" in the exhaust port?
I still need to polish up these ports. But here's after porting the bowl, removing that hump, port matching to the exhaust manifold, and cleaning up the casting imperfections.
Also, I noticed that the evo3 exhaust manifold and 1g exhaust manifold have a "hill" in their ports where they butt up to the head. Port matching the head makes the transition gradually fall then more quickly rise as you start to get into the exhaust runner. If you grab a spare you will see what I mean. It is like a very minute arc velocity stack (radiused entry). I plan on porting that "hill" to a more gradual reduction in runner diameter. If it IS meant to increase velocity, then I'm sure the more gradual change will be beneficial as a well built intake manifold has runners that more gradually shrink in diameter.Posted 09-30-2008 at 09:36 PM by dsm-onster
