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Chinewalker
01-19-2002, 12:56 PM
John`s Cars of Dallas has been in business for years and might be hated by purists, but are their V8 conversions reliable? It seems that there would be lots of converted Jags from the seventies and eighties available. Any opinions? I hope I haven`t opened a can of worms.

Doug
01-19-2002, 03:45 PM
I've seen some John's conversions and was very impressed as far as the kit goes. Of course, the devil is in the details and I've seen both extremes: cobbled up disasters and beautifully executed masterpieces.

There are plenty of converted Jags out there, most, I think, done on the cheap with a conversion kit and a used carburetor engine. A relatively cheap way to keep your Jag on the road if you happen to have a dead engine.

A really well engineered example with fuel injection, new components, etc would surely cost thousands.....more than overhauling the Jag 6-cylinder (12 cylinders may well be a different story!)

Personally, if I ever converted one it would be to gain *horsepower*, not becuase I think the Jaguar engine was so awful or unreliable.

As Jeb has often pointed out, the purists may scream .....but just think how many of these great cars have been saved from the scrapyard by an engine swap. I'd rather see 'em on the road with a V8 than see 'em in the junk pile.

Cheers
Doug

Steve
01-19-2002, 05:16 PM
I don't disagree with a word that you said, I would like to add, however, that for some the swap would be an automatic choice, whatever the condition of the standard XK engine. The rationale behind this is that the V8 is more reliable, so you are not going to experience a breakdown. I suppose that you could call it preventive maintenance, but you could change your oil every five hundred miles for the rest of your life and still not pay out as much money. The XK engine would love new oil that often! Most failures are caused by neglect.

Doug
01-20-2002, 12:06 AM
I not aware that the jag 6-cylinder is unreliable. The bottom end is bulletproof, the timing chains will last longer than any car....I can't really think of anything so bad about these motors.

A head gasket replacement may be needed at 100K-plus miles, but that's not so bad.

On my '87 Xj6 (115K miles) I use one quart of oil about every 2,000 miles and is does leave some drips now and then, but considering age and mileage, I don't consider that to be too terrible....and certainly nothing that I haven't seen on any number of typical V8's.

It is true, though, that, when the time comes, this motor can be very expensive to overhaul and I think that alone leads to many V8 swaps.

Of course, another advantage to the V8 swap is that you have a motor that is a familiar sight at any repair shop when you need repairs.

I'll agree that neglect is the biggest factor...

Cheers,
Doug

Basil
01-20-2002, 12:44 AM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Doug:
I not aware that the jag 6-cylinder is unreliable. The bottom end is bulletproof, the timing chains will last longer than any car....I can't really think of anything so bad about these motors.

&lt;snip&gt;<hr></blockquote>

As one who has owned abouy 7 Jags, I believe that the Jag's reputation for unreliability is due more to the electricals than the engine, which I agree is pretty much bullet proof (especially the bottom end). Neglect and improper maintenance probably another fator. Most of the "engine" trouble I had was due to things like the Alternator (electricals), or Voltage Regulator, relays, ect.

Basil

Steve
01-20-2002, 10:16 AM
The reputation that the XK motor has for being unreliable is, I agree, unfounded, but people on this side of the pond tended to treat them the way that they treated those V-8s. You could neglect the V-8 and it wouldn't bat an eyelid, but that XK straight six? It would protest!

Now the V-12. You want to talk about high maintenance? I would check the oil and coolant every other day, sometimes once a day, and change the oil religiously every thousand miles, owing to the car doing short journeys. 10mpg in town, 17 on a run. Those are the larger British gallons, mind you, but they're not that much larger!

Chinewalker
01-20-2002, 10:34 AM
Does anybody in the Dallas area know what the older John`s Cars conversions are selling for? There`s got to be plenty of them around.
The great British coachwork, styling, etc., coupled with 350V8 reliability has always intrigued me.

JBsZ06
11-09-2003, 09:14 AM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Steve:
The reputation that the XK motor has for being unreliable is, I agree, unfounded, but people on this side of the pond tended to treat them the way that they treated those V-8s. You could neglect the V-8 and it wouldn't bat an eyelid, but that XK straight six? It would protest!

Now the V-12. You want to talk about high maintenance? I would check the oil and coolant every other day, sometimes once a day, and change the oil religiously every thousand miles, owing to the car doing short journeys. 10mpg in town, 17 on a run. Those are the larger British gallons, mind you, but they're not that much larger!<hr></blockquote>


I don't know how you guys find the time to check the fluids and other important issues so often.

Your a lucky group...

I don't think I could do it yet I am quite envious of you guys...

Sort of makes the V8 conversion an interesting alternative.

Bugeye58
11-09-2003, 10:40 AM
Finding time for checking fluid levels and other important items is really easy, when you consider that the alternative is to walk to the bank and withdraw a large amount of cash!
Jeff

William Mapstone
12-14-2003, 12:23 AM
It is cheaper to build a high horsepower american V8 than to modify the Jaguar engines, but my understanding is that the 6 cylinders are pretty robust and will handle a lot of horsepower.

StevenA
12-14-2003, 12:40 PM
I have two XJ6s and both are original 6cyl... Mechanicals are just not a problem and the horsepower is way more than adequate. Electrical?... I just haven't had any more than the expected; Alt, starter, fuses, PCU, etc and by the way... I also have a Chevy with a FI v-6 and have replaced the same on it. AND.. the electrical on two late model Chevys that I have are both "Lucas" 100%.
The Chevy v-8 has a much more "macho" sound than "stock 6 cylinder", that may have started the switching idea. It has now become a semi-standard thing to do... but the improvement is questionable. One thing that is more readily available is "hop-up" parts for Chevy engines at local shops. It's a delima... But the weight of the cars overall is part of the problem. The engine weight is also a factor. If you use a Chevy rngine you will save a several hundred pounds in weight and that could translate to increase in speed. ????

vagt6
12-15-2003, 11:40 AM
I'm not a Jag guy but a great admirer. It is posted that the Jag 6 is often replaced by a V/8 for the power. If I remember correctly, the 4.2 litre Jag 6 came with about 265 HP, didn't it?

Could one of you Jag enthusiasts please confirm this?

Just curious from a LBC driver with 125 HP who can only dream of 265. . .

Chinewalker
12-15-2003, 03:56 PM
That figure would have been BHP, not the current method of rating HP which has been used for the past thirty years. Today it would be closer to 200-225 hp.

Roger
12-18-2003, 02:40 PM
Jag engines had a great reputation back in the UK for going on for ever, while the rest of the car fell apart around them.
I therefore reads this topic with wry amusement!

Chinewalker
12-18-2003, 03:19 PM
Parts cost and availability on Chevy V8s might just be a little more attractive than for Jaguar motors, don`t you think?

MattP
12-18-2003, 08:15 PM
In this thread the cost of an overhaul is mentioned several times, is that having it done or doing it yourself, or both?

I'm curious because the spouse is interested in an XJ6 particularly since she found out that if the rest of the car went south, we could put the heart into that SS100 kit.


MattP

John S Farrington
12-18-2003, 10:50 PM
When it comes to Jaguar V8 conversiona Iam a purist. The V8 retro has very little used car value. On the other hand, pure Jaguars in pristine condition, especially XK or XJ series 3 models are probably at the low end of the depriciation curve but will probably inrcease in value as a collector car. The V8 conversions that I have worked on are usually marginal in the conversion and leave a lot to be desired when comparing to a factory original. If your goal is to increase horsepower a well maintained Jag 4.2 liter has enough steam to gain you plenty of speeding tickets. My advice is to keep the Jag original and overhaul ar replace it. Overhaul costs for an XK or an XJ if you are dealing with someone who knows the engine are cerainly competive with doing an average V8 conversion and a high quality conversion would certainly exceed the Jag engine overhaul. (I have an exception with the V12 which will exceed $10K.) The Jag series 3 XJ6 and the Jag series 40 (88 and newer) have a very long life in between major maintenance. I work on (and have one of my own) have exceeded 150K miles and are still going strong. I know this has been a hodge podge of issues but think twice before going through a conversion. Tell me what type of Jaguar are you thinking of converting and I might add to the hodge podge.
Best regards Jack Farrington

Mark Beiser
12-19-2003, 02:59 AM
If you do decide to do the conversion, definatly use one of John's Cars kits. They are 100% bolt in, no cutting of anything, so if you keep the old origonal parts, you can go back to the Jag engine at a later date.

I have looked under the hood of 2 Jags and 1 TR7 that were converted using his kits. The kits themselves are very professional, but the quality of the job is obviously dependant on who puts it together and the general condition of the engine and transmission used...

I have no idea how it affects the value. It seems to me that converting a XJ6 would have a fairly neutral affect on the value of the car. Obviously it would reduce the value of a car that came with a V12. On the other hand, a XJ12 or XJS is more valuble with running V8 conversion than the same car with a blown V12...

If someone wants to do a V8 conversion on an E type, they should skip the conversion and sell the car to someone that can afford to own an E type. images/icons/wink.gif

JBsZ06
11-27-2004, 10:33 AM
Always an interesting alternative...

Do the V8 Jaguars have any problem passing emission testing in states like California or NJ?

Just curious..

Cottontop
11-27-2004, 05:15 PM
All,

There is a web site for V8 modified Jags of all types.

The URL is https://www.jag-lovers.org/lumps/

Lots of pictures and LOTS of conversion information.

Tim - www.ntahc.org/modifiedhealeys (https://www.ntahc.org/modifiedhealeys)

John S Farrington
12-02-2004, 11:27 AM
The comments above totally agree with my conclusions. The 6 cylinder Jag engines are adequately powerful and have great longevity built in (bulletproof past 200k miles). The V12 is a tour de force for engineering but demands high maintenance due to complexity and cramped space around the "large" engine compartment. Most of the problems of Jaguars are electrical in nature and most are due to improper or slipshod maintenance this side of the Atlantic. V8 conversions like Johns in Dallas are expensive and very dependent on the quality of the installation which varies widely. The average overhaul for a well used 6 cylinder Jag is about $4000. Compare this to a V8 conversion cost for a used V8 and there is no clear winner on the cost balance. If the V8 has to be overhauled it is the more expensive alternative. A Jaguar with the original power plant will always be easier to sell or trade. Most conversions go begging when on the selling block. Stay with the Jaguar power, enjoy and take good care of it!! Find a decent service outlet if you need it.

John S Farrington
12-02-2004, 09:15 PM
You have received very good advice for the most part on V8 conversion of Jag sedans. I will offer what I think is a summary flavored with my personal opinion. The six cylinder Jag engines are robust with adequate power. Their reliability has been tainted by poor maintenance on this side of the Atlantic. The six cylinder XK or XJ40 engine are high quality powerful units with great longevity provided that they are maintained properly. Most problems with XJ Jaguar models are electrical, not mechanical. The electrical problems usually are derived from improper and even ignorant maintenance and repairs. XK units may be overhauled for about $4000. XJ40 units are somewhat more expensive due to the more complex valve arrangement. I submit that a conversion costs a lot more, particularly if the V8 is to be reconditioned before it is installed. Both reconditioned units will have great longevity but the original Jaguar engine will have much greater resale value. I have seen V8 conversions go begging for another owner when placed on sale. A quick look at resale ads in most sources of Jaguar used cars will confirm this. My advice is to stay with the Jaguar 6 unless you cannot find or live with available sources of electrical/mechanical maintenance.
On anather note, the 12 cylinder Jags are magnificant, smooth and powerful units that are engineering tour de force. The cost of overhaul or head work among other factors make V8 replacement practical. Since the market for used V12s is not very good due to relativily high availability, complexity and engine inaccessibility that produce high maintenance costs. The situation is quite different. I still prefer and recommend staying with the Jaguar engine if you can bear the tariff. I would also recommend getting a Corvette if you want a Chevy V8. I hope that this discussion thouroughly confuses the Johns V8 conversion issue. Pureism and authenticity aside, long live the 4.2 liter XK engine!!

spit_head
12-02-2004, 11:19 PM
Why build up a stock 280 + Hp Jag. and want to compare it to a 180 to 210 Hp american anchor??? /ubbthreads/images/graemlins/hammer.gif

J. Christian
12-03-2004, 06:43 PM
I had been considering a transplant for my 1979 XJ6 (actually, that was the reason I bought it in the first place), but on further reflection, have decided to keep the Jag powerplant for exactly the reasons pointed out above. If it were a 12 cylinder in need of an overhaul, I might reconsider, but I have over 100,000 miles on mine, and after a tune up, it is plenty strong. The only change that I might make is to switch from the troublesome EFI to carbs.
I would also like to point out that this thread has been active for almost three years!! There are obviously people that feel quite strongly about both sides!