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By PF Arcand - 8 Years Ago
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This question should likely be posed to John Mummert..however I realize he is a very busy man & now sells new aluminum cylinder heads, & no longer offers head porting, so I'll try it here. Maybe someone who is well familiar with head porting can clearify it for me?. Quite some time ago, I obtained a copy of his published instructions in YBM on porting factory heads.. (sorry I don't currently have the issue #) Problem is, that there is one area that I just can't get straight in my head, no matter how many times I read it! On the 4th page of the instructions, a paragraph starts; "The vast majority of flow in both ports..... travels straight towards the head bolt (boss). Next sentence says " The best treatment of this boss is to grind an angled face to direct flow past it. (to the right) This is more important than trying to blend the boss into the right hand wall of the port up stream from the boss." Un quote. Did he mean the right hand wall, looking from the valve end? Further he stated; "remember there is practically zero flow on the right side of the upper port to within 1" of the head bolt. (boss). "Leaving a slight lip of about 3/32" where the right hand port wall meets the new angled surface of the head bolt boss, does not hurt flow." Unquote. Does he mean across from it, on the right wall looking from the top end? (it doesn't seem likely but ?) Or looking from the valve end up the right wall? I've read this section a number of times & just can't get it sorted out... ( I should mention that the copies I have are not that clear in spots & with the scanner I have, which isn't very compatible with our computer & copier, it's not practicle for me to make additional copies for others, sorry) Any informed advice appreciated. I don't want to mess up the spare set of "G" heads I have here. - Thanks.
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By Joe-JDC - 8 Years Ago
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While I haven't read that particular instruction manual, I have ported Ford heads and intakes since 1972, and quite a few of the Y-block heads and intakes. "Line of sight", is always where the airflow wants to go when the velocity picks up with rpm, and if you can get the flow to increase without shearing over the short turn, then the flow will always increase. Airflow reacts to shape, so you need to direct the air towards the center of the port if possible. That means on both ports, you need to put a curve in the inside wall to direct the airflow around the head bolt boss. Many porters just cut the wall until they remove the head bolt boss, to get more straight shot at the bowl, but that has its own problems with fuel dilution, oil control issues, and turbulence. Some folks cut the port as straight as possible, and then drill the head bolt boss out and insert a brass tube to reduce turbulence, or leaks. If you don't have much experience with porting, just a good deburring with a carbide or stone through the whole port will increase the airflow potential nearly 10%. I have also found that there is quite a bit of flow to be found around the pushrod hole boss if you can use large radius carbides, or round stones with 1/2", 3/4", or even 1" radius. I typically use a diamond double cut carbide in either flame shape, or oval shape with 6" shank to reach into the ports to rough cut the ports, and then use various grits of cartridge rolls to clean up the cuts left from the carbides. Having said all that, the Ford castings usually have wall thicknesses in the range of .200-.220", and you can feel safe removing at least .075-.100" of material without hitting water or making a hole in either the head bolt boss, or pushrod bend. I hope some of this makes sense to you. Good luck with the project. Joe-JDC
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By PF Arcand - 8 Years Ago
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Thanks Joe. I've read about some of your work in Y-block magazine. The info on casting thicknesses is very helpful, as it's often difficult to get an accurate feel for casting thickness, even using calipers etc.. I'm just doing a mild street port, as the block assembly currently has a stock cam etc. There's just a couple of areas there that I wrote about that had me somewhat confused..
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By Joe-JDC - 8 Years Ago
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Good luck! I just finished a pair of 113 posted heads, and they will be going to the shop for oversize valves and competition valve job next week. Lots of work to get them where I wanted, but I think they will be worth the effort for a street driven type engine. Got the exhaust manifolds ported to match the heads, and have Ted milling the iron intake carb plenum slots. These old wrists and shoulders rebel when I pick up an iron head anymore. LOL.
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