I bet flatdog has straightened henry ford out on a lot of things by now I hope they have flatheads and drag strips up there I sure miss that guy.
Interesting pics - appreciate the effort to show. Definitely jives with D-shaping the end exhaust ports and moving the opening as far toward the ends of the block as possible. Also illustrates the neck down right at the valve. I've slowly evolved my thinking on the relief - while your feeler gauges clearly shows what the likely entry into the chamber is, there is no question that the air must turn whether it likes to or not - once turned, it has a new direction of flow and the relief must help here - this is borne out in flow testing at higher lifts/flow rates.
The picture shown above has had the cylinder relieved over the valve and it is aprox .400 lift. The proflow valves when first coming off the seat has a much better flow visually because of the head being thinner where the stock valve is thicker at the seat, has to raise higher before there is the same path to the cylinder, hard to show in pictures but can see it when hands on. The regular SS valves has thicker heads but with a 30 degree cut at the bottom of the valve to match the valve seat helps it (again visually). I have made a cutter to try on the heads for valve clearance if needed, not at a true angle to either side (one side is about 4 degrees and the other side is about 6 degrees so settled on 5 degrees, tool is home made and hardened but maybe not enough for cast heads. I appreciate the input, makes for good reading and opens up for insight to the flathead. Vergil
I was told by a guy with a LOT of flowbench experience that, "we can talk ourselves into almost anything we want" - logic, while not necessarily going out the window, doesn't necessarily apply in some aspects of the flow dynamics specific to engines...while that seems almost counter-intuitive to me, the flow bench doesn't lie. Of course, as has been said countless times before, we don't race flow benches or dynos. That's why, in the end, I think we need to look at drag-strip validation of dyno numbers - and, in turn, dyno numbers that support flow-bench theory. In aviation, we have a saying - "clock to map to ground" - this is the normal way of dead reckoning navigation. You can do ground to map to clock and make things work, but it may not be repeatable. That's my fancy way of saying, I think we (and I include myself in this) get caught up in the latest flow testing or dyno testing of something, but the proof is always in the pudding - drag strip passes (by a relatively consistent driver with relatively consistent conditions) will give you a ballpark idea of what your HP really is (plenty of data points to work backwards from). Once there, you can figure which flow "enhancements" worked and which didn't based on comparative (and that's an important word - comparative) dyno tests validated the flow tests... Visually, it's easy to make a lot of assumptions that may, or may not, be true....
Dang Ernie. I was really enjoying all the pretty pictures and you had to type all those words. Now my head hurts. I really do get why a flathead would like a blower so much. I hope to build one someday. Now there is no question that it will be blown.
Well I don't do the drags for time slips and no access to dyno and no flow bench so can't give any input so will just read. Vergil
I found a site with a lot of port flow information from David Vizard, excellant information and something you would only find in a book or a classroom. Thanks Bruce for bringing his name up. Vergil forgot the link --- http://www.gofastnews.com/board/tec...orting-school-1-why-engines-need-airflow.html
Vergil Thanks again for the Show & Tell - beginning to learn too much info, gonna be dangerous soon. I'm heading for my machinist this week to talk about exposing the intake runners and building the injector blocks. Again Thanks
Have experiments ever been done with building a ski ramp that fits on top of the guides somehow? I suppose the trade off is always gonna be reduced size, but the more direct path may perhaps overcome that?
I,m not sure what you mean about 'ski ramp' on top of the guides, but I,ve heard that some of the oldtimers would braze a lump of brass on top of the guides and, grind and form it to make a smooth flow up an into the combustion chamber. At least thats what I think they were doing. I,m not sure as i,m not an expert. Seems that flow isnt about size, and what might look good isnt, I,ve heard about flow increasing in ports when a pencil is poked around the port while doing the testing, then it becomes 'magic'. Some have said that the exhaust flow isnt a big problem even tho it looks like it might be. My question is how did the hi dome piston work in Barney Navarro,s, flatheads? Seems it would breath pretty good.
I was meaning something that would fill the bottom of the port in the guide area, and I guess that's exactly what the brazing and filing would achieve, a nice steady slope up to the valve rather than the stock rightangle under the valve. Would take a heck of a lot of brazing.
along with maybe more compression on Barneys flatheads?? yes there was lots of brazing done baknthday, heads, combustion chambers, etc. they would remove the valve guides to braze them up.
Vergil as we know the installed valve spring hetght is affected by changes in the deck or valve eats. Any way you can give me a fairly accurate dimension from your cutaway? I'm looking for a dimension from the middle of the valve seat surface, in the deck, down to the top of the guide horse shoe clip. Probably a lot to ask I know but you have always been helpful to us flattie lovers. in the past JIM
Jim this is what I came up with, on this seat the dimension is within +.001" or -.001", hope this is what you want, if not let me know and will get it right next time. Vergil
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