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Found V12 pistons for 1990USD that's oversized and forged. Will give 9:1 in a pre HE engine.
I got no idea what that translates into in a HE.
should anyway be enough to get some more boost into the engine than standard.
Get someone to regrind the cams to better suit turbos.
if can get more lift and longer duration on the intake porting might not be necessary?
increasing port size would reduce gas speed and reducing low end volumetric efficiency and thereby reducing low end usable power.
with enough intercoling and pressure the power in the other end should not be a big problem?
some grinding to eliminate sharp edges that can create hotspots in the combustion chamber + new gaskets and bearings and the monster should be good to go right?
notice the curved large bowl for 9-1 comp ratio! after market pistons for PreHE. after 20 somethin yrs Japan showed the world how a detonation resistance piston chamber should be! prehe , 11.5-1 Cosworth piston NA. fuel required 104 octane or higher! old style factory piston , square bottom with valve reliefs, 10-1 ratio! has some squish around the edge thats a plus!
about street flavored turbo cams, short duration and close valve overlap is the prefered method unless you want extreme RPMs!
wide overlap will blow your boost out the exhaust when they are both open!
and 9 to 1 comp would be great(maybe 9.5 to 1)?
that silly HE chamber has to much heat rejection into the cooling jacket, possible detonation problems!
the pre HE chamber has a lower surface area , and slow to start detonation!
you mention forged , what does the piston chamber look like, any pix?
and fuel consumption should not be in the same sentence with 12 cylinders! they are NOT compatible,LOL.
ron
about street flavored turbo cams, short duration and close valve overlap is the prefered method unless you want extreme RPMs!
wide overlap will blow your boost out the exhaust when they are both open!
and 9 to 1 comp would be great(maybe 9.5 to 1)?
that silly HE chamber has to much heat rejection into the cooling jacket, possible detonation problems!
the pre HE chamber has a lower surface area , and slow to start detonation!
you mention forged , what does the piston chamber look like, any pix?
and fuel consumption should not be in the same sentence with 12 cylinders! they are NOT compatible,LOL.
ron
by longer duration I mean leaving the intake valve open much longer after btc and not more overlap. With a bow atmospheric pressure less overlap would be needed to get rid of combustion residue and the piston should be much more into its compression stroke before gasses start flowing the opposite way in the intake valve.
increased surface area should theoretically not itself lead to increased chance of detonation, but sharp edges do since the are thinner and easier heat up to temperatures where **** happens.
also a increase in area will statically increase the chance of hotspots.
Increased heat rejection will reduce the danger of knocking since the charge is cooler, but efficiency will suffer.
if I wanted fuel efficiency I would have a Japanese 3cyl midget car with a variable geometry turbo, but how cool would that be? However I see no harm in trying to get more for my money when I fill the tank
an increase in heat going to the water jackets of the head will allow the engine to run hotter and lead to the Famous V12 overheating problem!
i was at Daytona 24 races many times , and V12 Jags would often do well , BUT most when losing was the last 2/3 hrs because of overheating!
that piston chamber is a pretty good shape, but quite different from the orginal factory shape,as shown!
also no valve reliefs , means piston does not come all the way to top deck? very little squish?
but like i said put it all together and show us the results?
ron
an increase in heat going to the water jackets of the head will allow the engine to run hotter and lead to the Famous V12 overheating problem!
i was at Daytona 24 races many times , and V12 Jags would often do well , BUT most when losing was the last 2/3 hrs because of overheating!
that piston chamber is a pretty good shape, but quite different from the orginal factory shape,as shown!
but like i said put it all together and show us the results?
ron
Ron, some of the problem Group 44 had with overheating I believe is do to water short circuiting. If you look at the stock system the coolant hole sizes is the same at the front as the rear of the engine. Cool water enters the engine and exits through the coolant tube on top of each head. There is nothing forcing cool water all the way to the back of the engine and taking an equal amount of heat from each cylinder.
My race car which always ran cool, I put a plate on top of each water outlet and drilled a bigger and bigger hole in each plate. The front cylinder got a 1/4 steam hole with the back plate opened the full size of the gasket. The outlet going back into the radiator came from the firewall. Thus forcing the coolant to go all the way to the back of the engine before returning to the radiator.
To be fair it wasn’t my idea. I think I stole it from LUTZ in Australia. Whoever, it sure works. I used it on a single pass radiator without a bit of trouble.
Also since it’s collected at the firewall in the back of the engine compartment it’s self bleeding unlike the stock system.
Ron, some of the problem Group 44 had with overheating I believe is do to water short circuiting. If you look at the stock system the coolant hole sizes is the same at the front as the rear of the engine. Cool water enters the engine and exits through the coolant tube on top of each head. There is nothing forcing cool water all the way to the back of the engine and taking an equal amount of heat from each cylinder.
My race car which always ran cool, I put a plate on top of each water outlet and drilled a bigger and bigger hole in each plate. The front cylinder got a 1/4 steam hole with the back plate opened the full size of the gasket. The outlet going back into the radiator came from the firewall. Thus forcing the coolant to go all the way to the back of the engine before returning to the radiator.
To be fair it wasn’t my idea. I think I stole it from LUTZ in Australia. Whoever, it sure works. I used it on a single pass radiator without a bit of trouble.
Also since it’s collected at the firewall in the back of the engine compartment it’s self bleeding unlike the stock system.
that's a lot of useful information and make lots of sense. I would love to see a picture or 10 of this setup compared to the stock.
They recently made a new set for someone on this list, who, I'm afraid, wrongly, sounds intent on using in an NA situation.. which I doubt will work.
After an injection of development cash from Jaguar they were able to find changes to the std HE head that allowed them to hit their target goals, even under high RPM brutal usage.
Yeah sure, they had a constant supply of cold water to shed heat, but they did with both the pre-HE and HE, and the HE performed better.
~Paul K
Last edited by FerrariGuy; 01-17-2020 at 06:19 AM.
That’s interesting. From my flow bench experience I know air does not like to turn, especially sharp 90 degree turns which it would be forced to do in those recessed valve heads.
The prime advantage of the pre HE head (flatheads ) is the relatively gradual turns air makes as it enters the chambers. It doesn’t make any sharp turns at all until it finally hits the cylinder wall and even that is at a tangent rather than a straight on shot caused by Jaguar’s intent to impart swirl.
Ron, some of the problem Group 44 had with overheating I believe is do to water short circuiting. If you look at the stock system the coolant hole sizes is the same at the front as the rear of the engine. Cool water enters the engine and exits through the coolant tube on top of each head. There is nothing forcing cool water all the way to the back of the engine and taking an equal amount of heat from each cylinder.
My race car which always ran cool, I put a plate on top of each water outlet and drilled a bigger and bigger hole in each plate. The front cylinder got a 1/4 steam hole with the back plate opened the full size of the gasket. The outlet going back into the radiator came from the firewall. Thus forcing the coolant to go all the way to the back of the engine before returning to the radiator.
To be fair it wasn’t my idea. I think I stole it from LUTZ in Australia. Whoever, it sure works. I used it on a single pass radiator without a bit of trouble.
Also since it’s collected at the firewall in the back of the engine compartment it’s self bleeding unlike the stock system.
I'm willing to nag a little to get a few photos or/and a bunch of drawings of this setup
I know from my marine engineer background that a few marine diesels had individual valves on each cylinder to manually adjust flow to keep each cylinder working with minimal heat loss without getting temperatures so high that you would destroy something, but they had individual head for each cylinder.
That’s interesting. From my flow bench experience I know air does not like to turn, especially sharp 90 degree turns which it would be forced to do in those recessed valve heads.
The prime advantage of the pre HE head (flatheads ) is the relatively gradual turns air makes as it enters the chambers. It doesn’t make any sharp turns at all until it finally hits the cylinder wall and even that is at a tangent rather than a straight on shot caused by Jaguar’s intent to impart swirl.
The HE is giving higher efficiency so I guess you get more power back for the amount of fuel.
more flow won't matter much if you don't get burned gasses out. If the air in the overlapping stages only pass directly between the valves some exhaust gasses are left effectively preventing the cylinder from filling with a mix that can be compared. If 5% of the combusted gasses are left 4% extra flow won't help. I guess knowing this for sure is trough simulation and everything else is just observations and experience with a bit of guesswork.
The HE is giving higher efficiency so I guess you get more power back for the amount of fuel.
more flow won't matter much if you don't get burned gasses out. If the air in the overlapping stages only pass directly between the valves some exhaust gasses are left effectively preventing the cylinder from filling with a mix that can be compared. If 5% of the combusted gasses are left 4% extra flow won't help. I guess knowing this for sure is trough simulation and everything else is just observations and experience with a bit of guesswork.
Wow! It’s difficult to explain how wrong that statement is without detailing what achieved what.
The HE ( HE means Help Emissions) head is far worse than the pre HE ( Flathead) head.
The HE head recessed the valves which decreases the flow potential.*
The only good thing about the HE engine is the increase in compression ratio ( from 7.8-1 to 11.5-1 ) in US bound cars) and a slight improvement in the fuel injection system.
* with valves recessed into the head, air has to make a sharp turn to get into the cylinder and then get out of the cylinder.
Any “turn” in the flow direction decreases power and thus efficiency. If you have ever looked at the early Chevrolet six cylinder head, you will see the inspiration for that valve recession. Due credit is given when May called his head design the Fireball head which Chevrolet had been calling their six cylinder engine since its creation in the 1940’s
Realize the so called HE head was created to meet the coming California emission regulations. Not an increase in power! Since more than 50% of Jaguar sales was to California loss of sales to the California market would have been fatal to Jaguar who had made their biggest financial gamble making the V12 engine. Sir Lyons had been planning on a V12 engine since 1954, but it was only the sales success of the XKE and 3.8 sedan which gave him sufficient capitol to actually build a V12.
A secondary goal was to improve part throttle fuel mileage. That Jaguar did by changing final drive ratio (from a 3.07 to a 2.88) and a more efficient transmission From the cast Iron Borg Warner transmission designed in the early 1950’s to the aluminum Turbo 400 designed in the 1960’s.
Finally proof of the above statement can be found on AJ 6’s web pages. Peak power output in modified HE engines is about 450 horsepower while peak power output exceeded 750 horsepower with the early head. ( commonly called the Flathead )
Advocates of the HE head may try to confuse you with words like swirl and squish. Forgetting the swirl is imparted by the angle fuel and air enter the chamber caused by the intake port and in both head designs. And squish is generated by the raised edge on the piston.
Anyone have a chart that shows compression ratios of the v12 with different heads and pistons?
meaning mixing parts between the HE and preHE.
it is very simple, no chart needed. Flathead engines ( pre HE ) used a heron head designed piston. Heron head is a combustion chamber in the piston rather than the head. The prime advantage is increased airflow into and out of the cylinder.
In America the compression ratio was 7.8-1
while the rest of the world got 9.0-1 * the sole exception is the 1980 engine ( until May ) had 10.0-1
with the HE head the piston is flat topped and 11.5-1 until the 6.0 engine came out which had 11.0-1.
No you cannot use the HE pistons with the Flathead. The valves will hit the pistons and if you could relieve them the .375 needed to avoid collision the compression would be over 18.5-1. cylinder
Totally redoing this post because I think I made some math errors. What's below still has some errors, but I think it's due to inaccuracy in the exact chamber volumes and piston volumes:
This time I did the math for the hypothetical pre-HE piston with a 5.3L head, and the standard 5.3L and 6.0L systems.
Base Data:
5,343cc / 12 = 445cc per cylinder
5,993cc / 12 = 499cc per cylinder
Bore: 90mm (documented) 5.3L Stroke: 70mm (documented) 6.0L Stroke: 78.5mm (documented) Deck Height: 229.286mm (given by Norman Lutz) Rod Length: 151.4mm (documented) WristPinDia: 23.813mm (documented) Piston Skirt Clearance: 0.03 mm - 0.04 mm (documented for 5.3L) Compression Height:
s10an, with most of the information on JF site you will have at least 75% of mods required for more performance ,in a jag V12, i has taken Many yrs to gather it! from many people, from all over the world!
so just show us what you got !
talk is cheap , good engines are not!
and because the V12 is really old tech, most information was done without computers! many yrs ago!
also get the book by Allen Scott , he was chief engine builder for TWR , and Jaguar factory spent in the millions to get to where they were competative in class!
his final assumption was increased stroke would give more useable power than most other mods.
NO REPLACEMENT FOR DISPLACEMENT( except BOOST).
like all the power they made was only useable above 4500++ RPM.
for a race car YES ,lotsa top end mods RPM, for a fast street car TORQUE, all you can make!
ron
[QUOTE=S10an;2180969]if so simple then you can tell me exactly the compression ratio if a pre HE piston is put into a HE.[/QUO
if you are going for stroke your cheapest option is to buy a 6.0 liter engine. The first batch made was still a forging ( 93-mid 94. ). After that they were sintered Iron. In any case you are in custom made piston territory. The stroke will be determined by your crankshaft grinder. The stock rod journal is 2.300 and the Chevrolet connecting rods use will be 2.100 yielding approximately a .400 stroke. I say approximately because existing wear on the crank journal will alter that slightly..
I have always ground the crank and measured. Mind you that requires narrowing the Chevy Rods and bearings.
Shop for aftermarket rods. They are stronger and lighter and less expensive than new GM rods. . You will likely find it cheaper to buy 2 sets of 8 rather than buying 12 individual rods. Periodic sales are your best chance of buying at the lowest price.
Unless you are going for a cost no object engine and willing to get custom made connecting rods made and a new billet crankshaft turned. Then you are in territory I never explored.
At which point there are several good engine programs available so you can design your own modifications and try them in the virtual world before spending any real money.
Engine analyzer is what is on my computer. Make sure your numbers are valid and use good (repeatable) flow bench data as your base line. Make sure you measure each cylinder and each port. In the end rather than pay others I made my own flow bench. Although there are plenty available now at relatively modest cost. Then you can do an infinite variety of camshafts, compression ratios, headers sizes and lengths, timing etc.
or just use a GOOD V8 in it, and be fast,if thats your goal!
if wanting a fast lightweight engine use one of the Modern 4 cylinder TURBO engines(power to weight advantage)??
both ford and GM have some beauties,, would a 300/400 lb weight loss over the front wheels make a difference? old pic of GM ECOTEC 4 banger some dyno graphs of the same engine! notice the boost #s
i talked with the guys at GM Performance about this engine combo, what about just say 750HP , they said no problem doing that!
easy peasy?
ron
01-15-2020, 07:13 AM
