Xjeffs, pic of my TPS , 0-280 graduations , for my SDS fueling system!

potentiometer ,$3. dollars at electronic store!

 

 

if your gonna turbo then you would need a custom piston, todays cost are down , like $100. bucks each(12)!
also there is noway a GOOD turbo engine is gonna be cheap!
a good piston design will put more squish/swirl in chamber, have around a 9-1 comp ratio.
the stock early flat chamber heads would pull over 6500RPM , and proper cams and springs could raise it to over 7000+ revs!
and OLE has some experiance in custom flat heads (CNC etc).
my early 5.3 heads are hand ported , fitted with 3MM oversize inlet valves , 2MM over exhaust valves, custom and lightened ,polished, altho i MAYBE should have done 2mm inl.
and 3mm exhaust knowing the outlet ports are slightly flow resistant,,?
but nowhere as bad as later HE exh. ports!
to add the HERON chamber is highly resistent to detonation, thats why it needs a lot of ignition lead, good tuning will help take care of that!
as of right now i'm running 45 degrees total timing, and no sign detonation, 27yrs countin! with Euro 9-1 pistons in it!
custom SDS ECU , ,HI performance engines need ,TUNING-TUNING-TUNING!
ron

 

The piston being somewhat hemispherical is not a desired feature in an engine turbo or other wise. It's a liability. The piston being rounded or dished simply means it has more surface area and will absorb more heat. The head HE or other wise are flat and will absorb less heat. That's not ideal. The pistons aren't cooled and given enough boost (heat) the rings will expand to the point they crack the piston or drag the bore. Furthermore work done (Torque) is a function of cylinder pressure, a piston's shape doesn't matter all that much in this regard.

No one uses heron heads anymore... because it's an awful design with the only advantage being cost savings.

4 valve heads flow, no question about that. The Ferrari 458 GT has specific output of 126 HP/liter. But don't count out a well designed 2 valve head, for example Nascar engines have a specific output of 131 HP/ liter

 

The early V12 had the dubious distinction of being the first cars in the UK to require emission controls to meet the very lax emission standards there is the mid 70's.

The combustion chamber played a big part in that, and it was known at the time the flathead suffered from charge stagnation and poor combustion at part throttle. Jaguar had to compensate by running them overly rich, thus requiring exhaust treatment of all the unburned HC's.

 

No piston is perfect. There are area’s in even great 4 valve pistons that are under or poorly used. You’re dealing with a constantly moving and changing situation.
Our V12’s could be better but they are very good when limitations are considered. Jaguar tried 4 valve heads on their race cars and the power they gained wasn’t worth the weight they added at the top of the engine.
The HE heads suffer from poor flow compared to the early preHE ( Flathead design). Air flow is reduce when forced to make directional changes. Any combustion in the head requires two 90 degree turns.
Inducing additional swirl like the HE does further reduces flow.
The Flathead has swirl built into it the way the ports direct flow into the cylinder. Squish is taken care of by the flattened area at the edge of the piston.
Complaining about energy absorption due to greater surface area is like the left eye complaining about the right eye. It will happen in either the piston or the combustion chamber I know of no flat combustion chamber with a flat piston.
As far as fuel requirement, I’m a racer. Power is my sole goal. Fuel in America from the mid 70’s until the arrival of E85 was very substandard compared to England. That’s why England was able to use 9-1 compression while America suffered with 7.8-1. ( and made 37 less horsepower)
Ronbros is right using stock 9.0-1 pistons and the Flathead design for an affordable way to power.

I keep using the word cheap remembering the few sets of 9.0-1 compression pistons I got out of scrap engines. But out of fairness those are gone. As is my ability to spend money for custom forged pistons. Instead I sort through used components and select the best usable pieces. Laughing at those who spend money buying new. ( while wishing I could)

 

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Yes, that is what I say, the need of Pre HE tuning kits is not the masses. The most have HE and that is not suited for boost.

Ole M

 

That's a fantsy. Early Pre-HE heads suffer from no swirl and charge stagnation. So much so they had to boil the fuel with coolant pipe running through early manifolds. Squish event happen when a large discrete area creates shock wave in just 1 or 2 direction thus creating a vortex that homogenizes the mixture. This can not happen at the edges with a full thin rim in 360 directions. It's like a circular firing squad. Self defeating.

Modern pent roofs usually have 2 discrete areas for squish and early pent roofs that dont like the XK head have barrel roll facet aided by the valve angle that aids in charge mixing.

There is a reason no manufactures have used a flat head in last 40 years.

It would be my fantasy that someone would produce an V12 head the with a modern chamber the head. There has been talk of this in the past but no follow through. A few enterprising chaps have fitted AJ6 heads on a V12 that would be heavy but interesting.

 

The Jaguar factory made a few sets of 4 valve heads for the V12 and tried one set out in a race. The conclusion drawn was the slight power increase was offset by additional weight up high and not worth the added complexity. If you want I’ll look up the details for you.
As far as using the heated water from the heads that was due to the convoluted route taken by the carbs to get them to fit under the XKE hood. Used because the originally supplier failed to deliver the fuel injection as promised. Indeed the first system used the Bosch system X3 for the 12 cylinders.

 

Also Grp 44 had 4 sets cylinder head made 2 valve for preHE in California just before they shut down (Jaguar stopped the money)!
as i understand the Cali design company had a small chamber in head, and a small chamber on piston top, the two chambers worked together!
but ports were much bigger than stock, and flow tests designed, like a raised exhaust port, for straighter flow out!
and larger better inlet swirl,, (i sure would like to SEE one myself)!
44 finally made over 700HP engine along with over 7-L displacement!

 

I hear he’s selling them for something like £15,000. Plus intake manifolds.
Didnt Lister get something like 843 hp with their version of the V12? That’s pretty impressive considering they were running on French pump gas.

 

also some turbo MARINE Jag V12s engines made 1000hp , using nice cool ocean water to cool everything, you wont over heat the oceans!
i think? i hope!
imagine pumping 50 psi into inlet manifolds into a V12???

 

Hey Ole:

Nice job on this achievement! I am guessing you paid close attention to TWR and Jaguar's XJS by Allan Scott. A lot of that book talks about cam changes, upping the base circle and then messing about with profiles and timing. But my question is this: how did you get the torque numbers? Rather, what is the CR your engine is running?

Well done!

M

 

OLE, something i remember at the Big Daytona/Rolex 24 hr races , 44 and some private entrants , those with a big bore cylinders had trouble with blowing head gaskets!
i have seen sadly some run like 22/23 hrs only to DNF including Grp44!
and around 1997.1998, Lister brought over one of there cars, black coupe STORM, non turbo, empecable build quality!
it went off track at chicane , but coolant was blowing out anyway!
44 tried all kinds of bore sealing, including O-ring seals, but nothing was ever satisfactry, including the GAS filled rings!
have you taking thought about that noted head sealing issues? for long distance endurance engines?
ron

 

I remember the Lister Storm and I think I drove my XJSC to one of those Rolex 24 hours. Cool car.

 

Mike 90, pic of a V12 race piston 12.5 -1 comp ratio!
had pic for yrs, TWR,, looks like its been hand fettled one spot. it looks convex(camra to close), its flat top comes all the way up for sqwish.turbulence!

TWR race piston forged Cosworth, chamber centered in middle! for Flat chamber Heron type. they also milled heads flat by 050. thou. and the valves protruded from the surface reduce shrouding ,more flow, and custom valves, but factory sizes( MAYBE ?).

 

 

I run 12-1 cr. And my cam is quite radical, and was developed after sqrutinising Allans book and also I simulate engines in software and I am able to match the camprofile to the manifolds and flow I am locked to use.

 

This is how I do it. I place the copper wire just at the back edge of the flame ring of the gasket, it protrudes aprox 0.3mm from the block. Bullet proof. Never had problems with gaskets with this way of doing it.