Your plan to start small and work up is good. This is what I am doing. I have started with the suspension, Which you will most likely need to do on what ever you buy. The chances of the rear brakes being shot are pretty high, as they are a PITA to do.

Next for me is to build a motor that is capable of handling boost, other wise it will be a 12 cylinder hand grenade. When the engine is running and I sorted out the new ECU and TCU I will add the supercharger.

 

so how would you run the belt system for a blower on the stock harmonic balancer?

 

the engine designation in my pontiac is L67. if youve got the same engine as me, then that should be the designation, provided its FWD. if its RWD, then the designation will be different. also the flywheel will be different.

 

Yes it is the L67 RWD here is pic off ebay. The engine mounts are different as well
VT VU VX WH L67 V6 SUPERCHARGED ECOTEC ENGINE COMPLETE | eBay

Here is a pic of the front of my engine during a radiator upgrade. This is something else you will need to do to ensure the V12 does not overheat due to age of Radiator.

The V12 is bulletproof but will drop valve seats if overheated too ofter or too much

 

how much boost do you think i could safely run on a flathead motor with may pistons?
6.5:1 compression sounds like itll be a real dog until its spooled up. but i guess i could run plenty of boost with that ratio.

 

may cylinder heads*

 

im a new member so the forum wont let me view the picture gallery yet. congrats on the L67. its my favorite engine of all time. ive got six 3800 powered cars.

ive seen a TON of jags in my area with faulty radiators, causing coolant to get in the trans, causing fatal trans malfunctions.

also, is there a way to edit previous posts? reading through 3 or 4 is getting difficult.

 

sorry after reading the whole post, this aint gonna ever happen.

fair weather dreamer!

 

A well modified V12 with stock pistons will make 450hp, but FI puts different loads on pistons. Also it is soooo tempting to up the boost for a bit more power and then detonation and bang hole in piston damaged liner and if you are really unlucky hole in the block.

 

ive never seen a hole in a piston, but since i sport a modded L67, which is an incredibly knock prone motor, i have seen my share of chipped pistons.

does the V12 have any knock sensors, knock management, or knock retard?

 

lol, thats what they said about my blown V6 motor swap. which is my DD BTW.

 

hey warrjon, that TT jag that you posted pics of on the first page. is it intercooled? beause i see a ton of piping. also what would be the best way to do the headers? i was thinking for mine i would run the headers back into the turbos with each turbo mounted under the car at the very back under the rear bumper, and run plumbing all the way to the front to try and keep the turbos as cool as possible. i see this guy has his turbos in front of the engine. im trying to picture how to run the exhaust on a setup like his.

 

Yes it runs twin intercoolers.

Remote turbo set is not an option on the XJS not enough room under the car for 4 pipes. There is not enough room under the car for a 3" exhaust without ground clearance issues. Where the turbos are mounted on Bruce's car is about the only place they will fit.

As I see it there are 2 ways of mounting turbo's. First is a custom manifold a log would do the job and the other is to turn the cast manifolds upside down and fabricate a mounting off that. Both options will require a fair amount of fabrication work. This is one reason I have almost decided to go down the CSC path instead of turbo. The CSC will be a far more simple installation with 1 mounting bracket and piping.

The Jag V12 makes a LOT of torque and I think a CSC with its topend bias will be a good match in my case as I have just changed my diff from 2.88 to 4.09. I was worried that I would suffer massive traction issues with the low ratio. I know that Bradleys twin whipple charged XJS with 3.54 had issues with 1st gear traction.

 

it would be nice if there was an aftermarket set of headers that i could modify.

hows it running with 4.09's? got plenty of bottom end? what did you get the gears out of? i thought 3.54's were the shortest gears you could run on a stock diff.

 

which heads are more flow effecient? the may heads or the flatheads?
is it possible to bore out the combustion chamber on a may head to reduce compression? any idea how far down you could get the compression by boring it?

 

let me say there are many available tube exhaust headers for Jag V12s!

and the cylinder heads you speak about where engineered by a swiss guy named MAY,, BUT Jaguar refered to them as HE or HIGH- EFFECINCY heads, but May payed tribute to the actual chamber designer USA Buick,he, Buick called them FIREBALL chambers. that buick engines used for around 30yrs.

GM bought buick in the late 1920s, hence the chamber, that finally ended up on inline six chevys, 218-235s.

basicly the chamber was a high turbulence as piston came up ,swirling the flame in circles, hence Fireball chamber.

May added a small groove , late in piston motion to give the swirl an extra motion.

but the design did have some drawbacks, poor breathing at high RPM.

but good torque at mid rpm range, great for a street car.

so most race guys used the FH or flat head design for more up top power.

and IMO, any metal taking out of chamber would upset squish area, and induce more detonation possibilites, and increase crack possibles.


OK that said , your experience with hi-performance engines, you really never seen a holed piston?? HMM.
or the edges melted off, rings stuck in the groove from melted aluminum, really?

jag V12 knock sensors, not on early 5.3s, but ford upgraded all electronics, and if performance is your goal , go with the 6.0L V12, torque is king.

and not denying warrjon, i think remote twin turbs, is a very resonable choice,
up front mounted turbs would be a nightmare of engineering, along with I/Cs.

you would not need large diameter piping , 2 1/4 more than adequte,
it would be like turboing two inline 6 engines.

plenty of room in back where mufflers used to be, for turbos, mounted on rubber hanger donut thingies,((thats what i use on one of my turbo cars)).

hot pipes back and cold pipes up, to the TBs on inlet manifolds, NO I/Cs,
use auxilary injection system to control detonation.

stock 6.0L comp ratio, BUT you would need a standalone ECU-EMS, for com[plete control of fueling and ignition.

you can build any kind of hi-performance engine but the real key is TUNING, thats where the magic starts!

and 6.5 ratio would take a 1/2 hour to spool, by the time you got any usable boost, i'd be long gone uncle john.

things to keep in mind hi-comp reduces turbo lag, try to make mid range torque and let HP #s take care of themselves.

enough ranting!!! and yes a 4L80E is a great trans, but for some unknown reason a manual trans is much better, kinda hard to explain, but proof is it works great.

i hope some of this helps?

ron
i have owned both!

 

hell yeah, now theres a reply. Thanks Ron
now when referring to the 6.0L are you talking TWR jags or the mid 90 jags?
ive never seen a melted piston but ive seen a ton of chipped ones. mostly from too much KR, predet, then BAM.
and for the remote turbos, thats exactly what i was thinking. right where the mufflers are.

pretty sure the manual trans is better cause its about a metric ton lighter.
could you give me a link to a vendor that sells headers for the V12? ive looked and looked and looked and looked.

 

BTW those are KILLER side pipes. is that an HE? its got the pre facelift headlamps.
what are your performance mods?

 

I have done a considerable amount of research into the different options of forced induction for my XJS. My objectives are:-

It has to be a street car and capable of driving long distances.
Looking for between 550-650hp with good midrange.
It has to remain standard looking I do not want supercharger through the bonnet or massive flared guards.
And it has to fit within my budget which is not unlimited.


I was originally hell bent on a twin turbo setup, and researched remote TT as these are used on Corvettes with great success.

Issues - there is only 180mm of room in the rear muffler channels which is not enough to house the turbos without cutting into the boot. There would need to be 4 pipes between turbos and engine, the room between the transmission and floor pan is 100mm absolute allowing 2mm gap between the pipes leaves 94mm, if a 2" exhaust is used this leaves enough room for a 1.7" intake pipe - not big enough for the power. There is not enough room to get the intake pipe back into the engine bay without causing ground clearance issues. I can not get my trolley jack under the front subframe as it is and my car runs standard ride height.

Next on my list was TT with turbos mounted up front where the air cleaners are currently located, in my opinion the ONLY place they will fit without cutting into the body of the car. A good option I pondered over for a long time. Only draw backs I can see are the fabrication of customer turbo headers or mounts.

PD superchargers (Twin) one on each side mounted to the intake plenums another good option but adding considerable weight up front something I did not want.

Single PD supercharger - can not mount it in the valley without it poking through the bonnet, would also cause servicing issues restricting access to the plugs. Distributor would have to go. Side mounting the SC is possible but would be very tight and then would have 2 different lengths of pipe from the SC outlet to the throttle bodies certainly not ideal.

Twin CSC this would work and would be a reletively simple installation (Lister did this with the 700hp MkIII XJS). So maybe this could be done with a single CSCinto a manifold with equal length pipes to each side of the engine. This has merit simple installation 1 CSC to puchase and there are many running around on 6L LS1's etc. The V12 has bucket loads of torque so low down response is not going to be an issue espacially as I plan to increase capacity. May as well as I have to lower the CR so new pistons and Chev rods are in the build plan with the smaller rod journal I can have the crank offset ground for the 2.1" rods and gain another 10mm of stroke.

Other upgrades you will need to do if you want the car to last more than a few burnouts.

The rear end will need to be braced or you will rip it out of the car if you make 500+hp. The TT V12 race car has a brace running from the diff plate along the boot floor and the floor of the boot is rippled from the force applied and this car makes around 600hp with 300mm slicks

The cooling system will need to be serviced or you could end up with dropped valve seat and an expensive head rebuild.

A Custom ECU would also have to used to allow tuning of the fuel map

The compression will need to lowered if HE or 1980 pre-HE

Bolting 6.0L V12 heads to a 5.3L will lower the CR to around 10:1 as these heads have larger chambers than the 5.3L heads to keep CR to 11:1

Easiest way to lower CR is to fit a thicker head gasket or a decompression plate. Bruce's TT V12 race car uses a decompression plate.

cheers
Warren

 

i was looking into the Flathead jags. in the u.s. the earlier ones 75-78 are running anywhere between 9:1 and 7:1.
i dont plan on making crazy power. im gonna go with a couple of small, fast spooling turbos, remote mounted. i dont want to push the limits of the stock engine. then ill build up an engine in my free time if i can find a good source for parts, bearings, gaskets, etc.

or ill keep it stock until i get an engine built up, then just do a direct swap like my L67 build.