Has anyone done the sm block chevy conv.?Who has better kits Broken Kitty or Johns? Is there hood clearance issues? Is the much room ? Is it worth it? Any advise appreciated.

 

Just curious...why do you want to?

I don't have any experience with this process, so I've not help to offer.

Thanks,

John
1987 XJ-S V12
64,000 miles

 

Mine doesnt run. Seems like everything I ve read states that these v12 are very tempermental and not so reliable. I m going to try carbs to eliminate feul injection. SBC with carb always runs for less $. But Not giving up on v12 yet.

 

Welcome the XJS board, Bc xj. You'll find plenty of thoughts on both sides of this issue

I can't speak to the quality / differences between Broken Kitty vs. John's Cars, but I hear that John's kit is the more comprehensive of the two. I may be wrong.

The general consensus seems to be that it's cheaper to get your V12 running properly than to do a conversion. Even if your V12 is shot, you can find a running when pulled example and swap that in for less than a conversion.

I couldn't see myself devolving from a smooth, silent V12 (ok or I6 too LOL) to a carbureted V8. The engines are the soul of these cars.

Perhaps you should start a thread asking for help diagnosing your car, and leave this one for the (friendly) bickering over lumping or not.

Also, any 25+ year old exotic can be temperamental and unreliable if it hasn't been maintained properly. The XJS is a serious bargain, parts are plentiful and reasonable. If you pay a mechanic to do everything you'll need deep pockets to get it completely sorted. But if you can do some of your own work, you will save a ton of money.

and post some pictures!!

 

FAIR WARNING: There are many Chevy conversion haters here that will try to dissuade you by suggesting the pushrod V8 is some how inferior.

John's cars kits are trash. Its a bunch of hacked bits. I believe that is the reason conversions get a bad name. Call Andrew at Jaguar specialties. If you buy his kit and follow his instructions you will end up with a reliable v8 jag that is nearly as smooth as the V12 and much faster and efficient. His kits are engineered with a simple but genius quality. I've done two conversions. I've replace a John's kit with a Jaguar specialities kits so I'm talking from experience.

There are many ways to do a chevy conversion. I'll detail some below.

LSx, could get expensive but offers the highest performance potential, most refinement and best fuel economy.

LT1, L03, L05 could be, by far, the fastest & least expensive way to go. You could get a good running donor V8 Chevy Impala, Buick Roadmaster, Caidllac Fleetwood and swap the complete drive train, use an aftermarket loom and retain the factory PCM. This is the last and best iteration of the original Small Block Chevy and offers excellent fuel economy, ample power, refinement and good value. Driveable donors usually can be had for 2000 to 3000 dollars. There are many of these cars that are cosmetically clapped out yet run perfect.

GEN1 carb or TPI. The original SBC has the most performance options and endless configurations but early carburetor version can be unrefined. TPI and TBI from 80's doner Camaro and Firebirds can be had for 2 to 3,000. Crate engines are also an option.

 

Some converts are carb hack jobs...doesn't have to be. LT1 with its sequential Fuel Injected v8, the LT1 is almost as smooth as the batch fire V12. LS motors are smoother. I know I've had all the above at the same time to directly compare. There may be other reasons to love the V12 but real world refinement isnt it's exclusive domain.

I purchased this complete engine, trans and accessories with 103k for $1200.00. I spent 500.00 to recondition the heads and 400.00 for an after market harness.


Conversions have been selling for strong prices recently too.
Jaguar XJS V8 Convers | eBay

 

I second the plug for Andrew at Jaguar Specialties. His kits are the best. He is very knowledgeable and offers great support for his products.

I have an LS1 in my XJ6. I like it a lot!

 

You wont find many people who've done XJS converts here. They've all been chased away, ridiculed, and berated so they seldom return. You may soon experience the vitriol that they did.

 

Who do you think you are offering a reasonable counterpoint?? I refute thee thusly:

V12



(this is in jest before the lumpers get upset - I think alternate power plants are great - but too many folks don't give the V12 a chance, not so much the 6)

 

My 2 bob's worth, if I was to swap motors I wouldn't go past an LSx, Find a written of one and go from there, motor gearbox loom computer the lot. Dellows in Australia also do a kit, there are so many cheap bell housings on Ebay and mounts you just make up.
The V12 problem's are simply in the electrics and ignition, after-market ECU and a set of coil packs , new wiring and 90% of troubles are gone. the motor is so much better then a chev of the same age, but agree the advanced LS motors offer so much more performance. I was going to do the same thing, but ended up buying another V12 donk and a five speed that is going to be a transplant on mine, and it will be setup with the new ECU and ignition, still a year or two off for that.
Good Luck.

 

I chose to put an L67 in my Jag before the end of this decade, not because it was easy but because it was hard. i think SBC engines are junk.

 

carbs aren't more reliable the injection, they are just easier for many to understand. The constantly changing air:fuel causes the engine to run rich and lean and causes cylinder wash with the choke out. This all leads to a much shorter engine life and less performance. A carb is not the solution, if it was 2014s would all have them.

notice all the people who whine about jaguar reliability aren't the ones that own them? You would think thats why they don't own them, but its more like thats what they tell themselves so they can be okay with never having tried.

The v12 is just an engine. If you can fix a cast chevy 350 then chances are you can make a forged v12 reliable

 

How is a SBC junk but the Buick with two less cylinders and a pan rail isnt. I cant see the logic there. Please explain. Is there something I'm missing?

 

 

Hey you guys definitely know your stuff.. I just recently purchased a xj with a 350 already in it. Im replacing It with a new one... any tips would be nice..ive never done this before.

 

TIPS? Kinda' broad but go with a 383 especially if you've got a 2.88 rear and a 3 speed auto. What direction are you going with....peformance hot rod? or cruiser? Carb or Fuel injection. I prefer FI for the reliability and drive-ability.

You should probably start a new thread with more details.

 

Put a V12 back in it.



Also, would a mod please correct the title of this thread to "conversion"? This way it will show up properly in searches.

Thanks

 

Again Personally, if your SBC needs replacing don't bother replacing it with the same, find yourself a good LS motor. Twice the economy twice the power and half the weight. Also if you want you get get them to perform better than anything else on the market at a fraction of the cost.

As far as an L67 goes, What are you thinking?

Now these are big words coming from me as I am NO FAN OF HOLDEN/CHEV!

 

Well im purchasing a rebuilt 350 to replace this one... save me time and $ afterwards ill replace most of the hoses since this guy had overheating and theyre all ugly now.

Sorry im not broad I mean tips as in if there's anything I should know or do while the motor is out ..or what not to do

Also is it ok to replace harmonic balancer or if it looks decent leave it. ?.


And I currebt havy navy blue seats... I found a v12 87 ...with red. Owner said he can sell me everything for 500 no rips or tears or fade...good deal ?

 

It is carb
Has a rochester right now...I guess for gas saving purposes
Block is a #3932388 w/ holley contender intake man.

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