I hate to hear that about copper head gaskets. I am still a little confused about quench being a concern on these heads with a pocket like the one in these HE heads. Am I wrong in asking if you take piston crown down, or relieve the combustion chamber, the net effect is the same? I've tried to educate myself, ask of those who know, but I am wading into uncharted waters is seems with the Jag V12.
At this point, I am on the only track I know to stay on. I will CC what I've done. If I don't have 9:1 or less, I may have to take my pistons back out. The reason I say 4-6lbs of boost, is because of net effective compression ratio. Here is the chart:
Static
Compress.
Ratio
Blower Boost Pressure (psi)
2 4 6 8 10 12 14 16 18 20 22 24 6.0:1 6.8:1 7.6:1 8.4:1 9.3:1 10.1:1 10.9:1 11.7:1 12.5:1 13.3:1 14.2:1 15.0:1 15.8:1 6.5:1 7.4:1 8.3:1 9.2:1 10.0:1 10.9:1 11.8:1 12.7:1 13.6:1 14.5:1 15.3:1 16.2:1 17.1:1 7.0:1 8.0:1 8.9:1 9.9:1 10.8:1 11.8:1 12.7:1 13.7:1 14.6:1 15.6:1 16.5:1 17.5:1 18.4:1 7.5:1 8.5:1 9.5:1 10.6:1 11.6:1 12.8:1 13.6:1 14.6:1 15.7:1 16.7:1 17.7:1 18.7:1 19.7:1 8.0:1 9.1:1 10.2:1 11.3:1 12.4:1 13.4:1 14.5:1 15.6:1 16.7:1 17.8:1 18.9:1 20.0:1 21.1:1 8.5:1 9.7:1 10.8:1 12.0:1 13.1:1 14.3:1 15.4:1 16.6:1 17.8:1 18.9:1 20.1:1 21.2:1 22.4:1 9.0:1 10.2:1 11.4:1 12.7:1 13.9:1 15.1:1 16.3:1 17.6:1 18.8:1 20.0:1 21.2:1 22.5:1 23.7:1 9.5:1 10.8:1 12.1:1 13.4:1 14.7:1 16.0:1 17.31 18.5:1 19.8:1 21.1:1 22.4:1 23.7:1 25.0:1 10.0:1 11.4:1 12.7:1 14.1:1 15.4:1 16.8:1 18.2:1 19.5:1 20.9:1 22.21 23.6:1 25.0:1 26.3:1 10.5:1 11.9:1 13.4:1 14.8:1 16.2:1 17.6:1 19.1:1 20.5:1 21.9:1 23.41 24.8:1 26.21 27.6:1 11.0:1 12.5:1 14.0:1 15.5:1 17.0:1 18.5:1 20.0:1 21.5:1 23.0:1 24.51 26.0:1 27.51 29.0:1
I feel what I am doing is going to dramatically increase the low end performance of this engine. The Jag V12 is a nice engine (to me), but low end has a lot to be desired.

 

Sorry guys....I thought it would copy and paste. At 9:1, 8 lbs of boost take you over 14:1 in net effective compression ratio. I want to drive this car, not hunt fuel for it.

 

Can you post a pic of the chamber.

 

The HE head has large quench area (see pic 2 pads circled). Quench cools the charge, like forcing gas through an orifice.

Its well known that small chambers make power, take a look at Cup Car heads, their chambers are small. In a HE head the benefit of dishing the piston under the valves is you can lift the valve further. A HE head without valve reliefs can not lift as far as flat head.

The Commodore here in Aus runs an L67 supercharged (similar to Buick Riviera) these engines are 8.5:1 and I have seen them run 18psi on stock internals.

 

SC6
Just in case it is useful, Roger Bywater has a very interesting book out about engine design, with a very good chapter on piston and combustion chamber design, called "Engine technology for the modern world".
As far as I could follow it, CR is only one part of the matter, the detailed configuration of the actual combustion chamber, including the piston's part in it, is vital in promoting even dispersal of the fuel so it will all burn, rather than having some of it condense out on the cylinder walls and thus do nothing useful. Promoting a swirling motion to the charge being the aim so the fuel gets whirled about and vaporises.
So it might be worth finding out a bit more about it, as you will certainly get two different results from altering the piston and altering the head, even if the CR you end up with is identical either way.
I know sod all about this matter, but I think my understanding of the Bywater chapter is that it is better to get the piston as close as possible to the head surface, at least round the perimeter of the piston, so fuel cannot "hide" down the crevice between the top of the piston and the top piston ring. So making the head chamber bigger to reduce CR might be better than shaving the piston top.
Great project, really interested in your results, good luck anyway
Greg

 

I will try and get that book. I've been trying to educate myself on supercharging via reading, and speaking with those who have actually done it. From what I have found, in normally aspirated engines, compression and combustion chamber along with other factors are key to power. Mainly because we are all working with atmospheric pressure for our air supply. However, from what I understand, combustion charge area is key in supercharging partly because the net effective compression goes up so dramatically. If starting with 11:1 as the 6.0 has, I would get about 17:1 with a supercharger. From what I have read, 7:1 would be ideal, but very hard ($$$$) to accomplish on the Jag V12. I have learned, and am continuing to learn a lot on something that I really have no experience in doing. There is another thread running on the 5.3 vs 6.0 that I posted about the shims, but is getting me even more info. Thanks to all who post on these forums.

 

The crevice area between the top of the piston and top ring is important, and in a NA engine ideally should be as small as possible, this reduces the lost charge trapped in this crevice, on a Chev this is about 0.150-0.190". On a FI engine the top ring land needs to be thicker to cope with the torture of boost 0.250" plus.

One issue with the V12 and ultra high CR's is lifting the head off the sleeve, TWR struggled with this in the XJS GrpA program.

With FI it's not just the net CR, the blower is forcing more air/fuel into the engine, with 100% VE running 1bar boost in a 5.3L engine will force 10.6L air/fuel into the cylinder. I love supercharged engines, I have had 3 supercharged and 4 turbocharged cars. A good twinscrew SC is the best FI bar far, (I remember you saying you had a Whipple) very efficient boost, and throttle response is instant and they continue to boost until redline.

With a PD SC you can run shorter intake runners as the SC will provide the velocity, the runners on my Mercedes AMG (this had an IHI twinscrew) were very short, but throttle response and low RPM torque were phenomenal.

 

gene , pretty much what all the guys are saying is correct.

so have at it, and show us all! all this talk about squish,swirl,quench of combustion ,compression ratio is for control of dreaded detonation(instant explosion of the flame front travel), so that combustion is smooth and effective push on the piston,(not a big bang).

and reading about 6.0 cams , i just might believe Pre-HE cams may be the best for performance use(using factory cams that is).

and i have found for FI supercharged engines, N/A factory cams are much more user freindly for tuning and smoothness, for a street engine

wild radical cams are for all out race engines. wide overlap cams blow the boost out the exhaust, you need cam timing that can close the inlet valve early trapping air(boost) and exhaust open late using more of combustion expansion! you would be surprised with a given supercharger, what psi #s can be made in the inlet manifold by just changing the cam shaft timing

i can only speak from experience of many years building and blowing up some along the way.

i built a 1000hp SBC with Roots blower in 1965, running 30% load of Nitromethane and 70% Methanol, ran a best of 7.20, at 200 mph,rail dragster!

YES, make torque ,let the max HP be what it is! for the street.

 

I really have no idea what will happen here. But most of the fun for me is the journey. I've purposely waited on trying to post too much on this project, as who knows what may happen? It certainly looks impressive with the blower there! Very unconventional turned up on its side to get it deep down in the valley. It sits a little less than 1/2" off of the valley cover plate, and hopefully I won't have to modify the hood.
It is a 3.3L Whipple twin screw. It will supply more than enough air for this engine. What started this thread is what I found when I went to install the Isky MX-5 cams into my 6.0 heads.

 

Keep up posted on your progress.

The MX5 cams have 0.415" lift IIRC which will require valve reliefs in the piston

 

Isky Racing Cams
They do not offer shaft for Jaguar

 

They don't advertise offering camshafts for Jaguar. But trust me, I have a pair to prove it. Isky box, Isky wrappings, Isky shims, Isky springs.

Re:The MX5 cams have 0.415" lift IIRC which will require valve reliefs in the piston
Thanks for this info. I will check that for sure!

 

Digging around on their site, I believe I found the cams listed in a PDF catalog. I'll see if I can find it...

Ah, here it is, page 183:
http://www.iskycams.com/downloads/2016IskyCatalog.pdf

Padre

 

Padre

 

sometimes cam companies buy cams from other reputel companies , and rebox them!

it can be more profitable for them, and springs and things can be more generic that could fit many engine combinations.

 

Padre
Although it says the cams for the V12 can be made, those cam duration figures are for the 4 valve AJ6 engine, not the V12.
Greg

 

Of course. But it's the only place referenced by Isky about V12 cams and it does gives you an idea of what the two grinds they'll do will look like (XM-2 and XM-3). I've read some references to people putting an XM-5 like cam in a V12, but nothing direct.

This is a very informative thread. Kudos guys!

Padre

 

http://www.pipercams.co.uk/pipercams/www/product_nav.php?type=C&cat=CM&man=10&engine=22

http://www.kentcams.com/product-manufacturer-models-parts/model/127/vehicletype/1/manufacturer/Jaguar/m/XJ12/

 

I have enjoyed the overwhelming support I have always received from the Jaguar community. This is a great hobby, especially when it goes right. If you guys know of a way to weld aluminum yourself, by all means let me know. I have to relocate 4 injectors as it appears, as well as some bracket making that has to be done. I will have to relocate the compressor at a minimum since I have to use the valley for the SC, deletion of distributor, and the long drive nose that will be required.

 

HTS2000 aluminium brazing rods these work great and are easy to use and can be brazed with a LPG torch