I just happen to have a mint pair of flat heads for sale- lol please do not think this colors my comments in any way. I have been building/ testing turbo systems since 1972. One of the most important items? with a any blower engine is the design of the combustion chamber. The flatheads used a poorly designed dished piston. IDEALY you want a dished piston- not a bathtub piston. AND you want a slightly dished combustion chamber. There is also a ratio of quench area to cylinder area. This quench can be done with the flathead/ piston. This double dish will give you a "soft" combustion chamber. This soft chamber is best suited for blower/ nitros apps. ALL H E heads are unsuitable for any high horsepower app. Why? the "pocket" around the ex valve creates a "violent" chamber. When you make about 375? hp the chamber will create 2 flame fronts. You will get violent detonation. I have seen this first hand. Or I This H.E. head produced the most violent detonation I have ever seen. ( melted half the piston and the top 3 rings) Short of eliminating the ex pocket there is nothing you can do to control the detonation with this chamber. IF you retard the timing to stop the detonation you will not be able to make more then 350-400? H.P. You might try a 12 nozzle water/ alky injection system. If you do get big nozzles. You can shoot huge amounts of water without losing any H.P. Chevy did tests on this 60? years ago. The max ratio is 50%- I.E. if your engine is using 200 lbs of fuel per hr(400hp)- you can shoot 100 lbs of water per hr. with no power loss. The 4000? hp pro mod cars use this individual nozzle water injection today.( dont know how much water they shoot) I dont know. how successful water injection will be on an HE engine. I would want to have an extra set of pistons when I tested it. Here are 2 comments on this engine 1, the 3.550 dia jag piston weighs more then a stock 4.250 dia.12 to1 bbc piston. B the jag connecting rod weigh more then a bbc connecting rod. C, lol you can put a 4 inch stroke crankshaft in these engines. and D (oh well) the ex port will be the limiting H.P. factor The more power you make the bigger radiator you will need The ex port puts huge amount of heat into the cooling system. 5,? sorry Another problem will be blowing into the stock intake manifold- put it on a flow bench- blow into it- just like the turbo will- check the flow at each runner- then you will see why you have A/F differences between the cyls.The stock intake manifold will easily support 600 N.A. hp Hapy new yr. scott .

 

pretty much sums it up, explained it!
altho GM has been playin around water injection 70yrs (not counting WW2), my father bought a new 1950 Cadillac , had fairly hi compression, ping going up hills in hot summer days!
went to local dealer and they put on an option, a water injection Glass jug, every one thought it was windshield washer, nope it had a small hose going into the air filter !
HEY the pinging stopped and dad was happy!
my personal experiance with water/alky was with a new 1962 Oldsmobile Turbo-Fire with the Aluminum 215 cu.in. V8, i guy brought one into shop, said NO [power.).
after much search NO boost, the water resivior was empty , filled it with GM fluid , and away he went !
a fun car BUT, big cube V8s were comin on line, and back then you cant beat cubic inches!
ron

 

pix of my Jag V12 shows dished piston, NOT the original drop center chamber !

pic of my present Jag chamber after market!

 

That GM fluid was nothing more than Windshield washer fluid with a different color dye in it. I know that’s basically what early Bombers had in WW 2 for “take off boost”. ( slightly more than the 15-20% methanol used I think it was closer to 45% methanol to water ratio to keep it from freezing at altitude.) Then the Military went to 115/145 gasoline and it wasn’t needed anymore.
Indecently the Germans didn’t have access to the same octane fuel which is the motivation to develop their jet engines.

Every decade or so someone stumbles upon it and thinks they’ve invented something new.

As far as the heron head design. It was a compromise. It’s what we have to work with but it isn’t terrible either. The fireball still is focused on the center of the piston and unlike the Hemi head design Sir Lyons came up with in WW2 while standing fire watch over the factory. It isn’t filled with corners and spaces that disrupt the air flow.
Once that valve starts to open the flow has all the way to the cylinder walls to get moving before it is obstructed. Since the flow even hits the cylinder wall tangentially the swirl helps rather than slows down flow.
Is it as good as a 4 valve low angle head at high RPM? No. But at lower RPM it’s better than the Hemi design.

While the factory tried a 4 valve head design, and yes it was capable of making more power but only at Higher RPM and the added weight up high like it was was enough of a disadvantage that the factory never pursued it further.

 

Hi The chamber in the HE head is simply too violent. It is not a "soft" chamber You will never make any h.p. with a chamber like that.. AND another thing lol the sunken ex valve killed the ex flow. I am sure the ex. residuals in the chamber did not help too. I had the both heads flowed. Even the ex port in the flat heads was not that good. Sorry the flow # are long gone. As I remember it, the short turn is junk- there is enough metal to fix that and the port did not have enough taper The stock intake is killer The air cleaner is actually the first restriction on the intake side.

 

While I agree with your assessment of the shape of the HE head and it’s potential to make power. The Flathead or PreHE’s combustion chamber is much better. What’s more as the intake valve opens the piston is moving down and there is no interference. The intake port generates swirl without the interference the HE head has.
The exhaust port on the Flathead or pre HE flows 95% of what the cleaned up intake port does when it’s generally considered 80% is all that’s needed ( remember exhaust is under pressure being forced out )

 

from jaguar engineering papers V12

 

Scott interesting that you do/did have a 409 Chevy , what body was it in ?
i happened when W series 348 engines were coming strong, also happened to buy a New crate 409 engine n 1961,installed it in a 1957 chevy belair 2 dr. 4 speed corvette box ,installed a TWO 4 barrel manifold and custom exhaust!
that car was 600lbs lighter than a full dress Impala coupe,, fast was not the right word for it on the street, thru 1961/1962 never got beat by anything in cluding vetts!
it could match or beat new 427- 1963/67s.
course like most of us shoulda, woulda,coulda , had it today!
ron