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i believe that the TWR heads could not use oversize valves ,per rules A series!
they could modify the ports but not valve size! Allen Scotts book about A series engines!
altho Grp. 44 were not limited to factory valve sizes!
the valves in my V12 Jag are 3MM oversize(inlets), 2MM over for Exhaust,, bought from 44 leftover stock, single piece forged Stainless steel!
ported and blended to the seats, Berrilyium exh.seats, now banned in race industry(i think).
ron
I meant A-series as in Austin Minis - they used to do a lot of work re-shaping the combustion chambers to remove shrouding of the valves.
That is where this idea came from.
I ported a set of HE heads 6.0L heads actually. As the engine has gone to 6.7L I opened the chambers as well as de-shrouding the valves. On the flow bench they flowed 25% more below 50% lift and about 10% more at peak lift, which was probably more to do with bowl and port work.
I ported a set of HE heads 6.0L heads actually. As the engine has gone to 6.7L I opened the chambers as well as de-shrouding the valves. On the flow bench they flowed 25% more below 50% lift and about 10% more at peak lift, which was probably more to do with bowl and port work.
If you had the opportunity at no signifigant cost...say engine is out not going anywhere any time soon, is any of this even worthwhile on a stock(ish) HE V12 at standard displacement?
If you had the opportunity at no signifigant cost...say engine is out not going anywhere any time soon, is any of this even worthwhile on a stock(ish) HE V12 at standard displacement?
I would say yes, certainly blueprinting is certainly a worthwhile effort. It's a LOT of work I have 100's of hours in these heads.
On a stock engine I would not take as much out of the chambers or CR will drop (which is why I opened the exhaust chamber.
Deshrouding the intake valve to increase low lift flow and cleaning up the horrible ports and port matching to the largest port will at least have the engine run smoother, if that is possible in the V12
This is what I accidentally found on Facebook.
Source Link cstrading.nl/
What do you mean and why are these dots - points?
As I understand it, this is a turbo engine. Why does this turbo need extra turbulence?
not that I could find, but im sure this would make a world of difference if you were stroking and using big cams.
Im debating doing this to my extra set of heads maybe for my next project.
Why not spend a few hundred dollars for a pair of early pre HE flatheads? Here’s why. When the valves open up on those the whole cylinder is wide open. 360 degrees
HE heads when the valve opens up the flow has to get around the recess before it’s in the cylinder. that's two 90 degree turns. If you’ve ever worked with a flow bench you’ll see how much that hurts flow. Same for the exhaust.
On both sets of heads the swirl is put into the cylinder by the angle it enters the heads
Now maybe you think H E stands for High Efficiency?
well explain this to me. The Pre Flathead Fuel injected engine makes 264 horsepower with 7.8-1 compression Right?
Now wouldn’t you think that going to 12.5-1 compression would greatly increase horsepower? So how much more power does the later HE make?
My opinion. Is California came up with tougher smog laws about them and since fully 50% of Jaguars cars are sold to California I think H E stands for Help Emissions.
My thinking is that in 10 years nobody will be able to find flathead heads anymore. If someone could come up with a way to make properly set up heheads for power. It would solve the pproblem of he heads and there scarcity.
I believe the company that did this head did it with a cnc. It appears to be how they do everything else.
Also I do have an ECU that does allow Individual adjustment of the fuel and spark to each cylinder. So it could be a solution or atleast a remedy to slight valuations in the combustion chamber
search the junkyards. I’ve seen early V12’s that have had engine fires sell for scrap metal prices. Yes an engine fire ruins wiring and makes a mess of hoses and vacuum lines. But it sure doesn’t affect the heads. I’ve pulled manifolds that are good and even carbs that are rebuildable ( not all but some)
yes some years only a relative handful of V12’s were made. But as a core to start from they are fine.
Check the date of those rusty wrecks too. There are still plenty to be found.
comparing the size of the valves V12 and XKE 4.2. inlet 35mm-42mm. forgot to measure exhaust
That’s brilliant!!! All these years whenever I wanted bigger valves I just modified Chevy Blanks to work. Picking up off the shelf parts that I can use excites me.
On the Flathead You don’t want to mess with the exhaust valve. Exhaust valves don’t need to flow more than 80% of what intakes do because exhaust is less dense than intake and it’s under pressure rather than in a “vacuum”
I was using 1.90 intake and stock exhaust. On my most powerful engine. The Exhaust port was totally stock and I found a fast and accurate way to port the intake. Using a vertical mill rather than trying to open the port up and get it to flow the same as all the other ports. It went from over 200 hours of hand porting and checking flow to 10 hours.
If you do have a CNC mill, is there a pattern/shape that does make the head perform?
It’s a trade off. Improve flow = lower compression. You can partially make that up by increasing timing. Notice the timing of the HE compared to the pre HE
However you simply cannot beat physics. Every time you force a change in direction of the intake charge or exhaust flow you lose horsepower.
That’s why the early “flat heads” or Pre HE are so superior. When the valves open it’s a straight shot into the cylinder.
Comments about fuel mileage are silly. We don’t own economy cars. We own performance cars. Power requires fuel. The more power the greater the fuel use.
Pure and simple the whole reason for the HE heads was to conform to the pending smog regulations. So they copied the early straight 8 Buick combustion chamber. Which had the side effect of slightly increasing fuel mileage. Much of the actual improvement comes from other fuel mileage improvements about the same time. Replace the 1940’s designed automatic with a more modern efficient Turbo 400. Taller gear ratio, Improvements in EFI.
08-27-2019, 04:09 PM
