anyone know anything about doing this? Ron bros has larger valves in his v12 id be wondering what anyone is using. and has anyone done any head modifacation like this? 41 cylinder heads cleaned ready for assembly | Flickr - Photo Sharing!

 

beautiful engine build up, notice the piston tops, that is as close to perfect for a jag V12 as you can do, some dunce put the pistons in out of order, and had valve to piston contact.

they did use pre heads, with custom pistons, looks like a big bore kit also, so big valves dont hit the liner edge! but it is possible to use standard bore and relieve the cutout.

anyway I LIKE IT! reminds me of mine back in 1995. how fast do you wanna go,, how much money you wanna spend

 

add to post, i got my big valves,intake & exhaust, 3mm over size, from GROUP 44 racing, from BOB Tullius, had some left over new stuff , along with new springs, and retainers.

then i sat down,for a weekend,with no one around, in front of my Serdi seat machine, and made all parts fit properly, i used lighter weight valves than those in the pix, back cut, tullipped and swirl polished , bowl matched the seats to pocket, and a final 3 angle seat.

i'm retired and sold the whole shop,AND I DO MISS IT!
but things change and time to move on.

i'll toss this in(i want to sell my Jag, and as you know it aint an ordinary Jag XJS)

 

i want to go fast. im looking to be able to build in the upper 500s when i get new engine management and ignition. im buying a 6.0 block ive located, stroking that to 84mm and having it re nitrided as well as using gm rods. using aluminum pistons. havent decided on forged or hypereutectic piston pistons with special bushed rods for smaller pins. and upgraded cams. im looking for valves about 1mm oversized

 

some good info in this thread, that engine is built like the Broadspeed engines,

the shape of the piston does produce effective squish, and the chamber is partly in the head, after some thought on it, it can be more refined than what we see! dont forget Broadspeed is 40yrs ago.

this thread is mentioned in the other V12 cyl. head posts.

 

In the UK the largest size is 1.8" inlets, these will work well in just about all larger engines of 6L + and are availble from the likes of Rob Beere etc. Large TWR and Gp 44 engines used 1.9 but these are a pain to get and really require offset guides to maximise their positions, they also require special cam blocks with offset followers; good luck.
The 1.8 inlets will require new seats and lots of opening out of the ports to justify the larger size. The original Group 'A' heads were done by Oselli (still exist) but to do the whole lot, seats porting and valves is quite a lot of money. You will also need higher lift cams, maybe larger followers with the cam blocks opened out and maybe even the cam covers strategically relieved. Then you need to pay for tunning the beast not forgetting those custom pistons you will need to ensure the big valves with their big lift dont make terminal contact.

 

I did in the past but modifications to the head consisted of port work on the intake. The exhaust port flows very well in the stock form. Too well in fact . In theory the exhaust need only flow 80% of the intake because the piston is forcing the spent fuel out rather than attempting to draw air and fuel into a vacuum created by the piston retracting.

Combustion shaping is done in the piston, not the head. There is no combustion chamber in the head which is a great blessing since flow is enhanced. Without the normal shape of the combustion chamber to limit or reduce flow.
The shape and direction of the intake port provide all the needed swirl required. Swirl induces tumbling which further mixes fuel with air. Under compression the fuel air mixture comes very close to the ideal hemispherical combustion. chamber.

 

Rob Beere racing sells a slightly oversized valve for both the intake and exhaust but IMHO the exhaust is a waste.
The stock exhaust already flows 94% of what the intake does and 80% flow rate is considered ideal. More than 80% and the flow volume isn’t sufficient to prevent tumbling which reduces flow at peak RPM. The result is little or no extraction which aides in increasing intake.
The easiest way to increase is using a vertical mill with a ball mill (measure intake port for optimium size.). Plunge cut the intake straight down with the head upside down. Then angle cut from the intake port. You’ll have to calculate each cut because all six are slightly different. At that point it takes very little to hand blend those two intersecting cuts together. The result will be really uniform flow rates compared to hand porting each one.

Plus the massive time savings compared to hand porting. It used to take me as much as 120 hours to get two heads done to my satisfaction and semi decent matches on flow rates.
Doing it on a vertical mill cut that down to less than 20 hours once I knew the correct angles to cut. Plus better flow rates and nearly perfect matches.

Mind you this is for all out racing engines. On the street these feel really doggy until you are up past 4500rom.

 

MG nice write up , you do know probably less than 5% of the guys on this site have no idea what a vertical mill looks like much less how to really use one!
may as well get a set of TWR race heads, some of them floating around Virginia area, and guy in Australia is making some new ones!
if gonna spend the money spend it big!

 

also i hate to say it, but the old Jaguar V12 is an Antique , and can,will never compete with new engines that are showing up in numbers,V8,V6,I4 turbo!
GM 4 cylinder on the dyno, over 1000HP , junkyards are loaded with 1000s of them , in stock form!

 

That’s reality, yesterday’s best is today’s trash. But the V 13’s are still a whole lotta fun. And pretty besides.
I want to go really retro on one. Mechanical fuel injection. Heck the hardware is all there. It would take a newer pump and 1&1/2 sets of old mechanical injectors. Careful shopping I bet I could do it under $200 Then buy a couple of EBay turbo’s put about 15 pounds of boost in and see what the old war horse will do.
probably not 1000 horsepower but certainly impressive.

 

i just reread your post, YIKES amighty, you say you can make a Jag V12 do 1000HP for $200. dollars!
well some of the guys here are gonna beaknockin?
ron

 

In a Top Gear episode they added nitrious (professionally) to a junk yard XJS V12 and it beat the whole lot of cars, porsche included. This was atleast 10 yrs ago. I believe it was pushing 550hp easily.

If I had another Jag and...another pile of cash to burn I'd simply bolt a twin turbine modern diesel truck turbo to the engine, get modern custom head bolts (that can withstand the pressure) and go from there.

If going all out on a fantasy engine build, I'd just convert the XJS to run diesel with the aforementioned twin turbine modern turbocharger, and some stronger studs. Ford uses them on the new trucks.

 

The head bolts are already plenty strong enough to live with moderate boost. The nuts holding the heads need a little help but they are readily available from ARP along with AN washers.
You can fit T2 turbo’s outside of the engine compartment but under the front fenders on a XJS But about 6 PSI is all you’ll achieve. 6 psi is about the most modern pump grade fuel will tolerate anyway.
If you’re going for bragging numbers and don’t want to lie, you might try T3’s to get over 10 psi. But you’re in on your own territory. plus you’d better plan on using windshield washer fluid as a supplement.( windshield washer fluid has about 10-20% methanol in it in addition to the water) remarkably, I buy a gallon for $1.99 at the grocery store.

Where do you live? Here in the USA we have E85 In The Midwest, 1 in 5 stations carry it. That’s 100 octane plus fuel that locally sells for $2.09 a gallon about 80 cents a gallon less expensive than the good premium that only provides 93 octane.

If you want to maximize your boost don’t use an intercooler. Every curve and bend in the tract from the turbo to the inlet reduces the flow, then going through the cooler to drop the temperature further reduces flow. Instead use the cooling properties of alcohol to reduce the likelihood of detonation. Pour some alcohol on your hand and feel it’s cooling properties. ( windshield washer fluid is even better, the water and alcohol massively cools the whole intake charge down even in our batch fired long inlet tract V12’s )
To get to the numbers you are talking about, you will need serious intake port work. But not hand porting!! Too much chance to make a mistake and hit water. Plus the variability between cylinders will really hurt power output.
We are talking a ball mill in a vertical mill. Doing it that way will not only get you better, safer results but save more than 110 hours of labor.
Yes bigger intake valves too. I used cut down titanium but be careful about the material the guides are made from.
Finally camshafts, since nobody is producing billet camshafts anymore for the V12 you’ll either have to pay the setup charge to run some or weld up the existing lobes. I don’t know if Kent will do that but Isky will and Crower used to (and still might)

 

again thats all simple enough, NO problems????

 

Sorry buddy, you need to spend a moment re- reading that
I said I could probably buy the pieces needed to go to mechanical fuel injection for under $200. ( check out racing junk.com )
Then buy a couple of EBay turbo’s. Even then I said probably not 1000 horsepower but impressive.
Last I saw EBay T3 turbo’s were going for $130 each. While I wouldn’t put them on an engine I expect to get 200,000 miles out of they aren’t complete junk either.

 

sorry guy , those old style turbo,s are junk relative to todays modern ballbearing pieces, with lots of computer engineering into them for reducing turbo lag by 50% better than old designs!
but you aint gonna find them in a junkyard?
a quik check around here , NO SAAB turbos available, ancient history!
Ebay turbos are not engineered for racing(could be applied tho), they are primarily for Trucks and HD off road equipment!
i am on some of those Chinese sites, contact me couple times a month with latest turbos and parts, NEW!
cheap turbos are cheap, hi quality performance turbos are expensive!
and for your interest check out Electric Turbos , they have made major improvments in them!
no more complcated piping systems!
ron

 

I’m sure you’re right.
I first turbo’d a V12 decades ago in the early days of Chump car racing. That’s endurance road racing for up to 24 hours. In cars worth $500 or less. ( you had to prove that) Sorry if you already knew that.
I took a roached out 1975 XJS that didn’t run. Got it running and put a pair of $35 junkyard Saab turbo’s that were still usable.( easy to test )

Prior to that I was big into Vintage racing. But by the time you got Weber’s, pistons cams etc etc etc it was easy to have $15,000+ and it never made as much power as that roached out turbo engine did.

Yes, if you can afford it, buy the good quality stuff. Especially if you don’t enjoy the mechanical aspects. Or the idea of a breakdown bothers you.
In fact, if either of those applies to you please don’t buy a Jaguar Unless it was made after Ford’s ownership took effect. And whatever you do, don’t modify an engine.

 

Breakdown. Hah. Following the advice of Grant, Doug, OrangeBlossom etc (and there are many I cant list you all) you shouldn't have a breakdown...not reaaaalllly. Now 4 years on I see it as a chance to do it all and do it right. If you own a Jag best advice is to drink heavily and own a backup Jag (or other car)