I keep going back and forth with myself on engine choices for a future XJC project. I want to build my engine first, then find the right coupe. I've had both the stock 4.2 XK and the SBC lump. I loved the way the TPI 350 drove (except for the TH350), but wasn't thrilled about the concept of having a Chevy engine in it. So far I go between a built up XK4.2 and an LS1. I enjoy the beauty of classic engines, a cleaned up XK is gorgeous, I would make it look more like one from an E-type than an XJ6. And I've never seen a more vintage looking engine in an XJ6. But I do have a practical side that reminds me of the POWER and TORQUE of the V8. And it would probably be cheaper to do a nice LS1 swap than to build up a 300HP XK4.2. I just want it to be fun to drive and handle well, a manual transmission will most likely bolt up behind either one. I'm not looking for it to be the fastest thing on the road, but neither do I want to be out-gunned by some suped-up Civic.

 

Hmmm, I vote for the XK engine. If you aren't trying to be demon fast with it, then get some more HP and torque from the 4.2 and enjoy the refined smoothness. Plus, it'll look so much better in the engine bay in my opinion. Either way though, it's your car and you need to do what will make you happy.

 

Agree. You pays your money and play the cards. A clean XK engine is a marvel. Although, the Bosch FI has great benefits, it isn't particularly pretty. The design was influenced by politics which make it a bit of an enigma. Beautiful cross flow alloy head with DOHC. Best breathing available and conducive to high rpm. Yet, it is an undersquare crank and bore?? Piston speed limits rpm and the engine does best at delivering torque at moderate rpm's. Why, cuz engines are taxed by bore dimension in the country of origin.

Now, a manual transmission with at least five speeds would be a giant leap forward over the outdated BW.

My car is a lump. 94 Cadillac LT! with 4l60E transmission. Not the hottest of the LT's, but designed for the torque needed for the Fleetwood Brougham it was destined for. Big car and heavy. As our Jaguars are far from light weights, the match is good.
And, it pulls the .70 OD and 2.88 rear ratio with aplomb. But, watch out for those hot civics. Weight to power ratios, you know. But, my car is no hot rod, but gets under way if pushed quite handily.

An LS1 is even better.

Each can be beautified quite nicely.

Carl

 

These old Cats are becoming fewer. In 10 more years a refined old Cat with an XK engine will garner many more raves than one with a GM piece of iron in her. Gotta think downstream on how much more classic the car will be with a Jag iron in her. Just my 2 cents.

 

Having owned four (4) Lumped Jags...I can voice my opinion. Modern stuff versus dinosaur technology???

Easy to work on, reliable, better power and mileage...parts are available anywhere...

Your only concerns will be the Jag components still left in the car...with the hood down, no one can tell but you and those cars that you pass.

Wish I could justify taking out my brand new (1995) ZZ4 383/200R combo and replace it with a LS7 or LS9 and modern (6) speed automatic.

 

So why not fit a Jaguar AJ6 or even better, an AJ16 engine ?

These engines are the most reliable Jaguar ever made bar none. If you can find one, even a few supercharged ones were made. There is also the last of the V12s, a 6 litre lump that was pretty reliable, although very few were made. And, of course, plenty of the Jaguar V8s must be around, incl. supercharged too.

I would not go for an XK, unless you can get one of the very latest ones made with the slotted block. The XK was an old engine in the 70s and antediluvian in the early 80s. It is a pre-war design with a post-war cylinder head; magnificent in a way, but its getting harder and harder to support these engines now.

 

If your coupe is factory original leave it alone because it will be more valuable as an original. If it needs other extensive repairs or is just too far gone to be a survivor then lump it. I lumped both my coupes because both needed significant rust repairs and both needed new engines.

I've owned many jags and a Chevy conversion is the way to go. Very reliable, almost limitless engine characteristics... everything from 180hp smooth torque econo-cruiser to 500hp hi revving hi-po monster. The AJ engines are great but the availability and cost of replacement parts has to be considered. Also the ZF transmission is no great asset, lazy shifts and expensive to repair.

 

Does anyone know if the XK and AJ are closely related at all? For instance, could the aluminum AJ6 block be used with XK6 heads and carbs?

 

Nope.

Other than basic layout.....both being straight sixes with DOHC configuration..... there's noting at all in common between the two.


Cheers
DD

 

Went on errands in my XJ wuzza six. The Grosvenor Brown gleamed in the sunlight. Six feet away, outshone a few much new cars in the park lots. Even with the primered scar from a super extended door misadventure. I chose a brown primer to protect yet, not stick out like the proverbial sore.... Main reason, more Kibble for Coco. He as a tremendous appetite.

The LT1 purred, but jumped when asked!! Nasty Bimmer!!

Analyze:

Use a spread sheet.

Columns. Engine trans combos. Price. Availabilty. Kit available. Kit cost Pros Cons.

Alter as needed til it's time to do what I wrote a paper on in my former profession

DECIDE
.

 

Oops!!

Add:

Execute

Carl

aDD;

eXEUTEC

 

I have one of the last BL XJ6s made. (BRG with tan hides) I love the car and know it is a relic by today's standards of power, etc. The old 4.2 dual overhead cam six sometimes strains under the 2 tons of the cat. I also have an XK8 and she's overpowered (if there is such a concept). I know the desire to put some good Chevy V8 power under the hood of the XJ6 would feel like it were the right thing for a more drivable car, BUT, something about popping the hood and looking at that bank of classic long twin valve covers. Sorry, just will live with the often under power for the thought that I own a true work of engineering and art combined.

 

I'm really leaning towards a 4.2, and it might be going into a MkII instead of an XJC. I'm looking for a junk motor for free(or next to it) to build into a 250-300HP moster. I've seen 300+HP in 4.2 E-Types, so I know it can certainly be done. A mild 4.2 sqwapped into a MKII seems to be a fun drive from what I've seen, I think a properly built XK would be perfect. I love the sound, and it's my most favorite motor to simply look at. I love the polished DOHC valve covers and Webers / ITB's. Beautiful. I've decided, Thank you all. Anyone know of any good threads to follow on a 4.2 build?

 

Well, changing out a good 4.2 for an SBC just for the heck of it doesn't seem the way to go. Especially in an otherwise pristine car. Now, if the 4.2 has a major issue including just plain tuckered out, the picture changes. A proper rebuild ain't cheap. OTH, decent SBC's are widely available in various guises at a wide range of pricing.
Now, in a modified car, it seems more fitting. Even if it is just paint, wheels, air dams, etc. or in resuscitating a blown and tuckered out entire car.

I faced that dilemma. 0 compression in all six holed meant bad things. I chose to lump. A budget for the rebuild was huge. Even just a head job. Shop rates around here are $125.00 per hour. Well, the lumping probably cost about the same. I dared not add it up!! But, it came out very well.

I sold off some small stuff and gave some away. There were no takers for selling ghe engine core or the good BW 66. I gave them away for home peace and to claer the driveway.

As to pricing of an original car vs a modified car, who really knows. No reliable way to conduct a meaningful analysis. Both are definitely, wiling seller vs willing buyer.

PS, I really did like my car as powered by the 4.2. Something new to me.

 

For my XJC, I've come to the conclusion that keeping it near original is best, aside from a few cosmetic changes (which could be undone). Mainly due to the rarity of these cars.

If you want to modify and put a different engine/ transmission it then I would go the whole hog and build something that looked like the one in the Avengers, maybe with the supercharged engine from an xjr. !!!!

If it was a four door xj then the engine change would not be so much of an issue IMO.

 

That was a Broadspeed Coupe. When I get an XJC, I'll most likely swap a late XJ6 engine into it with a few tweaks to give it maybe 20-30 more hp. I want it slightly quicker and still torquey.

 

Don't rip out what makes a jaguar special. I'm new to this forum but I am adamantly opposed to V8 engine swaps. Would you put a Ford 5.0 engine in your 65 corvette because it is better on fuel or more reliable? 2 door or 4 door XJs should all remain original. It is not ' the thing to do ' as I see all too commonly in ads.
Want a V8 car with leather seats? Buy an Impala.
Rant over - sorry people.

Solo out...

 

How about the XJR/6 engine?

Still a six, but gobs of torque due to the addition of the blower.

 

SMOG day for me and the jaguar yesterday!! Dropped the 4l60E into second and cruised around town a bit. Then a short run on the freeway. No drop into OD that way and torque converter locks quickly and stays that way til I release it with a touch of brake pedal. Plenty of go. Object, heat the converters well.

Same old shop as always, but in new location. At first the tech was a gasp. 'You got to go to a special station if you made an engine change, as the youg gopher looked agape'. "Yup, done that" said I as I opened the rear door and displayed the special data decal with the bar code that enabled connection to his machine and remote to Sacramento. A lot of non descript middle aged cars there. Mine was easily the oldest, but the best looking. Rivaled only by a mid nineties Corvette. Odd, the engines are kin!

Oh, passed. good for another two years.

Now, tax prep to tackle.

I thought I had retired years ago???

Carl

 

Special? How so? High priced, difficult & frustrating repairs is special? Getting stuck is special? Running one minute, dead the next is special? Underpowered, inefficient is special? Special...I think you mean infamous.

Welcome to the Forum. You're adamant opposition is interesting but Why? Carol Shelby did engine swaps? Ford Beat Ferrari with a pushrod V8? Low mileage factory originals may belong on a trailer in a climate controlled garage, or in a museum..if the owner chooses. High mileage daily drivers just need to work at a price and with reliability.

Generally...you wouldn't replace a great Chevy motor with a great Ford motor. Some people do put modern Chevy engines with fuel injection in to classic Corvettes. That would make more sense than a ford because it fits easily. In any case the 65 Corvette is iconic and some are worth hundreds of thousands of dollars. An XJ is not a Corvette. This is a terrible comparison if considering market value .

Most Jaguars that are lumped would have been scrapped otherwise. Just one example....Late 80's BMW 7 series are hard to find still on the road. Just like Jag's they suffer electrical and engine issues that require high priced repairs. Yet you will still find many 70's and mid 80's XJ's around because lumping is an option that keeps them on the road. The 80's BMW 7 series has very high scrappage rates and most of them disappeared after the cash for clunkers program.

I have seen more than one helicopter Turbine engine in a Porsche...I wouldn't do it but people are free to do with their vehicles as they wish with in the law.

By any quantifiable metric lumping a Jag makes sense unless the vehicle is an all original well running survivor and there are not many of those still around.
If you factor in intangibles such as romance, desire, history, originality then it's a different matter or judgment that each owner should be free to make on their own with the feedback they may seek from others.

Why an Impala? That's it's a silly and very narrow suggestion...Jag made V8 cars in the 90's and still does. Many other manufactures have too.