Hello all!

Im going to put an Edelbrock EFI Chevy 350 in my XJ12.
My V12 engine is dead. Block is cracked.
It already has the GM 700 R4 tranny in it.

What is the maximum power and torque that the rear end, axles, etc. can take?

Id like to put in the 440 HP and 410 TQ engine.

Thanks!!

John

 

John:


Where do you get those HP and torque numbers for a 350?


The center section of the rear is either Dana or Saginaw. Plenty sturdy and favorites of the Hot rod guys.


Carl

 

Should work fine, my ZZ4 383 crate engine has 407 HP and 470 torque and has been in there working for years...

 

Dana 44 is plenty strong, My jag is well over 450 HP and has quite a few hard launches on the track, Diff is the strongest thing on the car. Everything else needs upgrading.


Impossible to get those HP with 350 and a self tuning EFI system. Self tuning EFI uses a wide band O2 and thus requires a mild cam with lots of LSA. No way to get those HP figures on a mild cam 350. Build a 406 with AFR heads and a real MPFI system with DIS. Even with a mild cam and 440 HP is starting point. Same for LS but just double the price price.

 

Edelbrock performer 383 EFI is where those numbers came from.
They make good stuff & crate engines.
Thanks for the advice!
JWW

 

jww427

Are you planning to use their Surge Tank for the needed high pressure for the FI?

I was considering their system but converted to new S3 tanks and Pollak tank switching valve. Always wondered how well it would work and where I could install it in the engine compartment???
I have their heads on my engine and the conversion is best done with engine mounts from Jaguar Specialties... I like the trans mount from JTR best and used it in my SII 383/700R... easy to make and good access to the trans should any servicing need to be done.

 

This may be a silly question, but can the new Jaguar supercharged V8 fit?
Im guessing it would be expensive, but it would retain its heritage.
Anyone know someone who's done it?

 

Here is a video showing one in a older Jag... would be a tough install... plus your SBC would be faster and easier to install and fix afterwards.. plus it has been done many times..

 

Extremely difficult to do physically and electrically. Physically the later Jag V8's are front sump so the sump would hit the cross member. I've seen an XJS race car with an AJV8 on these forums but the engine was set far back past the firewall and the cross member still needed to be modified.

The easiest modern engine Jag swap is the AJ6 / AJ16 and the AJ16 supercharged variant. These engines and transmission basically bolt in and are very transplant-able technologically speaking. The AJ16 supercharged is a great and practical high performance swap, I6 smoothness with supercharged power right at the limit of what these older chassis' can handle with out major upgrades.

 

Im thinking perhaps an LS3 430 bhp unit.
How hard is it with all the electronics?
I know Andrew of Jag Specialties has done a few.

Ill think about the Jag AJ16 with blower.

 

I would use a LSx engine if doing the conversion today. Andrew has done several and his assistance is priceless.

 

I know a couple of folks have used a racing fuel cell instead of the 2 wing tanks.
How would a fuel cell affect the handling?
Thanks!
John

 

Do check with Jag Specialities on their opinion regarding the rear cage mountings. When these saloons were raced by people in the UK with big power engines I believe the mountings were converted to be solid as the rubber mounts can't take the torque. The British Leyland XJC V12 racers also broke the hub carriers too. Mind you, their V12 were putting out 600 bhp, a lot more than your proposed engine !. So it's not just a matter of putting in a powerful engine, the rear drive has to be upgraded. If you have to solidly mount the rear cage, you'll lose a lot of refinement.

 

So what are you going to do with all that power ? Lose your license to drive, bump up your insurance rates after a few speeding citations..? Public transportation is not that bad..
After owning a 427/435 Corvette back in the sixties ,..400 hp in a 4000 lb car simply does not do much for me.. 10 lbs to 1 hp ratio with 2.88 gears..hmmm.. But as mentioned the cage twist is the problem. The car was not designed for this.

 

Probably has 3:31 gears, I do not know where you get the idea of cage twist? I have had (4) Jag Lumps and drive my S1 everyday... no rear IRS problems over many years. The IRS is probably
one of the best made Jaguar items... if you want bad, talk about the wipers or AC performances!!!

Plus, the SWB S1 does not weigh 4000 lbs, was 3593 with the Jaguar engine.. would be about 2-300 pounds lighter with SBC and aluminum heads and modern radiator.

 

Aside from the fact my car is over 40 years old and rust prone, and I gave my word I wouldn't drive it in the rain unless Absolutely unavoidable, the fact that the wipers positively suck pond water is a Huge deterrent to driving in rain!

There! I've said it!
(';')

 

Cage twist is the name that I commonly use for the IRS's eliptical movement that expresses itself as wheel hop, juddder and loss of traction under hard acceleration. In extreme cases the IRS can rotate so much the rear bushes rip out and the drive shaft bangs on the floor board creating quite a racket in the car. I have my own solution to the the matter that involves some bars and a nice large bushing which offers control with no harshness. Track tested too. For me with it happened when my 1st SBC project approached 400HP with 235 series tires.

This "cage twist" is often experienced with most setups with engines that produce over 350HP and have sufficient traction to generate the force necessary to over stress the IRS's rubber mounting. Generally a high performance tire, 235 and larger will generate enough traction to re-create this phenomenon IF IF IF you have enough power.

There are MANY solutions to this issue. One was even employed by Aston Martin on the Vantage. Very necessary with it's 285 series rear tires, 420HP and 3:54 rear gears.

For those that dont know, Aston Martin used the Jag IRS we all know and love until 2003. Here is how they solved what I call cage twist.





Shown here as part 82

Here is how another forum member solved it.
https://www.jaguarforums.com/forum/x...1/#post1481911

Check out how this issues was solved on this Twin super charged XJS... also from NY.
Bradley Smith XJS in Detail

Here how it was solved on this 7.0L V12- Very nice!
Lister XJS MkIII 7 litre SOLD - XJS & XJ from KWE Cars





Here is how Fiboy did it.

 

1. A couple of weeks ago, I took my Jaguar out in the rain. A ploy to enable a shorter wait at the Smog station. It worked. The wipers managed to handle the rain. A bit over a drizzle. In a full on storm???
And, they parked correctly, sans the Andrachuk move....
I went to market yesterday. Ugh, it is spattered. Needs a wash. We are promised spring weather this week. Dare I deter that by washing the Jaguar???


2. Rob Wade was a past lister on J-L. His XJS drop top was a Jaguar-Specialties conversion. Rob warmed it up a bit and took it to the drag strip. Rob made a traction control device that defeated the cage twist issue. Custom exhaust systems are his stock in trade. he made a beauty for the XJS!!!!


3. My LT1 is conservatively rated at a mere 260 HB. But, tuned so that it's 300 + torgue comes in early. Not enough to strain the cage, for sure. but, quite lively.


4. Alyn. You have it. A "few'" racing tickets and bye bye insurance. Hello very expensive assigned risk policy for $'S!!!!


Carl