Have you read Doc Dutra's old article from the Slant Six Racing News?
www.dutra.org/doug/draft-webpages/porting/ssrn-article.doc
There's also an article that talks about the newer vs older heads:
http://www.slantsix.org/articles/combustion-chamber/sl6-combustion-chamber.htm
Fourth post down on this one has some flow numbers with various mods:
http://speedtalk.com/forum/viewtopic.php?f=1&t=22094
Really stupid question and I am only asking it just so there is no doubt in my mind but you said ..........It does add a small amount of volume to the port itself...........I am assuming at this point that this is exactly what we do not want. We want to reduce the amount of volume to the port itself.Any smoothing you do will give some results. Whther or not it's enough when combined with other mods to make a feelable difference is anyone's guess. But - you won't hurt anything by leaving a larger hole there. It does add a small amount of volume to the port itself, but like Kid mentioned - these heads are so bad that it takes a lot to make them good. It's just reality - not bashing. If you really want to "fix it right" then have the holes welded up and reshape the bowl. This will require the entire head be rebuilt because of the heating required and the distortion - but if that's also part of the plan then welding isn't a big expense. I also don't think it will give you much better performance so the cost vs reward issue comes into play there too.
This is great information and a big help for me, I am a bit confused though. You mention looking at the head in installed position....rectangular hole, top of rectangle is the roof and the bottom of rectangle is the floor.....so that means when flipping the head over and looking at the combustion chamber/port we would be looking at the roof of the head.I have no pics, but here are some simple terms:
Looking directly at the port in normal installed position: the floor is the bottom, the walls are the sides and the roof is the top. Now flip the head on its back, with the chambers up toward you.
With the valve removed, the bowl is what you see if you look down pass the valve seat.
Doc's recommendations are what I have always done as well; I think we may have read the same books when we were kids,
You don't want to lower the floor, or the bottom of the runner. I have found that the most "bang for the buck" ( the most effect with the least effort and time involved) is to "blend the bowls", that is, removing the casting flash just below the valve seat ( careful not to hit your valve seats!) and grinding off the big blockey bosses that often stick down where the valves stems come through the head into the bowls. Then you can "gasket match", which is matching up the openings between your intake manifold and the head so they run directly into each other without a "step" where the two meet.
Another thing I do is to open my headers or exhaust manifold slightly larger ( about 3/32) than the exhaust port opening in order to create an anti-reversing effect, or A.R., and polish the exhaust ports. This is easy to do, since headers are usually larger than stock openings anyway.
That is a pretty head, can you tell me how you got it so clean? Did you do any combustion chamber work?Here is a close-up of my slant head....it will be getting oversize valves fitted.
Thanks Bill. so it sounds like that little knub will have to go away completely. Is that your take on it too?Here's a little brighter shot of the original picture. Hope it helps...
Thanks Bill. so it sounds like that little knub will have to go away completely. Is that your take on it too?
Great looking head toad, thanks for the link as well. I plan to use some of the pictures for another up-coming question.Use the pics in this link as a reference
http://www.slantsix.org/forum/viewtopic.php?t=38066
Might be that is part of it as well :read2:1930,maybe the excess (hump) is to support the valve guide area for longevity.The slant was engineered as a work horse.Just a thought.
That is a pretty head, can you tell me how you got it so clean? Did you do any combustion chamber work?
I'm going to be rebuilding a couple heads for a local guy to go to the 2 Mopars hes got with Slant 6's in them so, I'm following along, not the first time I've played, but....it has been awhile so, a refresher won't hurt any!