nice, who made the piston forgings?

those look to leave some finishing work?

and that is a very good idea, so you can finish and adjust compression ratio,and piston to head clearence., squish/quench etc.

what bore size, and suggested stroke?

also the bowl is offset to match sparkplug position, NICE , keep the combustion in the piston NOT in a head chamber!

 

They are for a customers engine.
Cost.. an issue? :-) The cost is just right.
If you need a set we can discuss if you need rings, pins, coating and so on.
Package prices available if you need rods and cams also.

V12 rods in H or I profile. And billet cams in any profile.






Ole Mobeck

 

The Gr.A pistons in the Picture in the previous post are finished with correct comp height to fit rod length, stroke and headgasket thickness for the customers engine. Also the dish volume is ready to make the right comp ratio.

They may look unfinished due to milling pattern but that is not an issue. Also the top is turned so they get a better visual finish at the Crown top.

The Gr.A pistons are for 90.5 bore and 70 stroke. Room for valves with +1mm oversize from std.

I try to make pistons symetric so they fit everywhere in the engine.

Here you see some other pistons I delivered, they are for 96 bore and Space for 40 and 48mm valves.
With 86mm stroke and 7500ccm they will give you 12.5-1 comp ratio and capable of cams With more then 6mm lift at tdc.

 

7.5L Jag V12 12.5 comp ratio, then i would need a complete Heavy Duty drivetrain?

Mobeck ,beautiful stuff.

what is the black metal coating you use, also what friction material on piston skirt?

ron

 

Mobeck,
a question...
what do you do for the Main Caps?
as above 400lbs/ft the tend to crack I am told...
need to be fettled to remove stress raisers...


and do you do headers that will fit an 1992-1995 XJS

 

Those pistons are for a customer's engine, certainly not a xj road car.

The black stuff is the look you get when you nitride harden tool steel.
These cams are billett cams, not from castings. You dont find enough room for good profiles inside regrinded std cams or castings available. Therefore nitride hardened Billet's

Ont the shirts there is a moly coating for less friction and wear.
Next batch pistons I consider to anodize for even more durability.
We'll see if someone want a set.

 

I have not seen problems on the more moderate engines that see only 5500 rpm but With huge Power. I have a feeling its the rpm that kills the main caps but I dont know for shure. Maybe someone have seen problems and can tell about it.
But sometime you hear about Things and never get to know the actual cause of the problems. So I dont always beleive what I hear.
But if you want there is available steel mains caps from a man in UK.

I do headers yes but only as custom builds as I tune them to each engine configuration and use.
For mass produced headers I have seen the type VA Spiteri sell. They look real good. But I dont know if they fit LHD cars.

 

I asked Norman Lutz about this as I was concerned this could happen with my 6.7L engine. He assured me that all of the 500+hp V12's he has built (and this is a lot) he has never had a cracked main cap. A lot of these engines were built for Hydroplanes so they were turning at or above 7500rpm for extended periods.

 

I have come across 5 cracked caps! Having put up pics , the internal memo about what to do to remove the stress raisers and pics of an engine where the caps have been modified (6.7 road car) I sigh. Just maybe TWR Group 44 Broadspeed Lister all got it wrong. All the XJR15's with their near standard 6L engines have the modded standard caps. TWR wasted their time/ money doing this? Upto you chaps.
The pistons with the Black coating are mine BTW The finish is top its the flash and a trick of the light in the photos I took
As always your cars your choice.

 

Yup, but the black coating I refered to was the Nitride billett camshaft.
The Next pistonset may as well be anodised.

But there is a real big difference in a professinal built race engine that will se only stress in its Whole life and a beefed up street engine that see 100% throttle 5% of its time... TWR Group 44 Broadspeed and Lister didnt get it all wrong, but they where used in a different manner than a dreamt about street engine today.
BTW it was you I had in mind when I said there are steel main caps available :-)

 

question; who owns or drives the Jaguar Grp C ,XJR-12 race car at last weeks Spa Classic race? Silk Cut car

it was a Silk Cut car, they also had a XJR-15 car running there!

it is now on You tube

 

Shaun Lynne is the driver/ owner of the XJR12 , I have supplied suspension and bodywork but no engine parts.

I will guess the XJR15 was David Bradbury, a customer of mine.

 

don't worry... I have DL'ed you main cap mods and when I even get to get into my v12
they will get the proper treatment... (I hate surprises) my 1275 did not spin to 9k with out the "details"

 

As discussed previously Bonner Engineering in the UK made a revision to the May HE head called the B head with a revised combustion chamber and valve setup. I'm not going for 500Hp from my 5.3 more along the lines of improved performance with vastly improved efficiency using throttle bodies and a Motec system.

Mr Bonner is making up a set of heads for me and I thought people might enjoy a picture of the combustion area which is unique but similar to a Weslake type design and along the lines of where Chevrolet were heading with their 2 valve designs.

We are doing some before and after dyno comparisons.

This may be covered elsewhere but was there ever a fully counter weighted crank for the v12 and if so did it still need the crank damper?

 

Brilliant. Thanks for posting this. Any further details/close-ups greatly appreciated. Those heads look as though the pocketed exhaust valve has been reduced in size, and a decent chamber is in the head. What will be the compression ratio when all is done? And what are the projected Torque and BHP figures?
Do keep us up to date with progress.
Greg

 

Will post more pictures as it comes along. This is for a road car so looking at 160 BMEP at 5750 rpm which gives around 375hp. With more development of the exhaust and inlet runner length potentially 400hp from the standard displacement. Compression ratio will be 10:1. Going to 11:1 is an extra 4% power but with added fuel and timing complexity.

My current flathead 5.3 produces 218 hp on a rolling road and gets 8 mpg on four Strombergs. If a good internal combustion engine is 30 percent efficient I would say mine is about 15 percent hence the effort to improve both performance and efficiency and lessen the smell of unburnt fuel.

 

Will you be running this head on carbs or F.I.?
Greg

 

That chamber volume must be close to 40cc if that's correct then the max CR with the piston coming to 1mm from the head would be 8.7:1 unless you use a dome piston.

The other problem with the HE head is the location of the spark plug which is more offset than the flat head.

V12 cranks do not need counter weights, just balance the rotating assembly, pistons rods etc.

 

Rather than starting a new thread I'll ask it here.

shooting for higher horsepower and wondering what you guys think of basically the opposite way of building the v12. Rather than stroking it by adding a bigger crank (I have the 5.3 pre he) and boring it out, what about just boring it out and keeping the stock crank? Not technically a destroked engine but the increase in bore will effectively lower the piston speed at high rpm.

I'm looking to build a high rpm screamer. Thinking of sleeving and boring it out to a set amount, say 95mm, keeping the 70mm crank, big cams with stiffer valve springs/titanium retainers. For intake I'm thinking ITB's from a BMW m3.

all controlled by megasquirt. I'm thinking the MS3 is what I will need with ford EDIS wasted spark setup. Or would a coil on plug setup work with megasquirt?

 

.

that is all doable , be interesting build, general consensus is Jag V12 suffers from its short stroke for good torque production in in the low rpm ranges.

you will be making new pistons ,and 6.0L cranks are showing up, so may as well make pistons to fit the stroke. Jag V12 never had a problem with piston speeds anyway.

MS good choice , you would deffenatly need a standalone ECU for adjustability of fuel and ignition maps.

and a hi rpm screamer would need a manual trans to make proper use of the rpm.

i dont know what cam/valve train you plan, but the biggest thing is the Jag V12 suffers badly in its hi rpm BREATHING ability, cylinder heads where engineered for smooth driving and not useable much past 5000RPM, there are heads available,but costs are way up there!

but like said here on many posts, go for it just .
keep posted with pix!

are you speaking about the V12 pre-HE or HE engine?

ron