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The project is a series ii XJ coupe and it will eat the V12 for breakfast.
electrical is sorted diffs are sorted trans is sorted
will post as we go if people are interested otherwise will show it finished in a few months
Well if you’d like to increase its value at the same time you increase horsepower to over 500 and get your V8 why not put a supercharged DOHC 4 valve V8 Jaguar engine in it?
Such a engine change would be considered by most enthusiasts as an upgrade rather than a mere lumping.
I’ve seen several such cars auctioned off at modest prices after body damage has them totaled. Just for information here in America because of liability laws it takes relatively minor damage to total a car with body damage.
I tried looking into getting 450-500hp to my V12. The parts to achieve this are rarer than rocking horse **** and are not massed produced.
I am dropping a 2015 6.2L LSA into another Jag project (561HP - 560TQ) as spending £56,000 ($110,00NZD) for a 500HP V12 engine upgrade was simply rediculous and out of the question.
300HP is not quite enough for me and the LSA was the only option
Craig
!.
dont waste money on little LS type engines , jump up to Big boy toys, at least a 454 BBC chevy, or a 572 CU.in. easy 750HP 850/1000FTlbs torque!
dont waste money on a little LS type engine jump up to the big boy toy,, at least a 454 BBC chevy, you can but NEW 572, if you need 750/900 dependable HP! with a warentee.
ron
dont waste money on little LS type engines , jump up to Big boy toys, at least a 454 BBC chevy, or a 572 CU.in. easy 750HP 850/1000FTlbs torque!
dont waste money on a little LS type engine jump up to the big boy toy,, at least a 454 BBC chevy, you can but NEW 572, if you need 750/900 dependable HP! with a warentee.
ron
Thought about that but want modern smooth reliable power with a 6 speed double OD Tranny. Remember this aint that small. 9 pound boosted 6.2 LS3. (Equivalent to a 10 litre engine at that boost)
plus very easy to up-rate the power with the ECU
she aint no toy Ron!
Last edited by Crackerbuzz; Sep 6, 2019 at 12:14 PM.
Well if you’d like to increase its value at the same time you increase horsepower to over 500 and get your V8 why not put a supercharged DOHC 4 valve V8 Jaguar engine in it?
Such a engine change would be considered by most enthusiasts as an upgrade rather than a mere lumping.
I’ve seen several such cars auctioned off at modest prices after body damage has them totaled. Just for information here in America because of liability laws it takes relatively minor damage to total a car with body damage.
Thought about that too MG...
The GM LS engines are my preference and easier to work on and easier to get parts for. Not building to sell. Building to drive!
The GM LS engines are my preference and easier to work on and easier to get parts for. Not building to sell. Building to drive!
I understand some people just like the complexity of pushrods and rocker arms. If that’s your choice, it’s OK. Don’t feel bad. Hold your head up high, just ignore the comments and barbs from knowledgeable enthusiasts. While most race cars and high end cars stopped using pushrods and rocker arms a long time ago, not all did.
There is even a class for those called NASCAR. Now the “Good Ol’ Boys” may look down at you for putting it in a Jaguar instead of its actual home, the Corvette or a pickup, go ahead, dare to be different.
Good luck.
oh speaking of pickup trucks, the best selling pickup truck in the world , the Ford F-150 stopped using pushrods and rocker arms a long time ago.
just found some OLD PIX , 1989, my Camaro BBC 467 inch, aluminum race heads, all forged inside ,big Holly, sorry no pix of engine!
and it was a TOY play car, all these type cars are toys, not very usefull except to play racer! that includes my XJS roadster! 1982 INDY pace car, BBC 1988/2006, pass anything but the gas stations! YUP just a FUN toy! Wheel dynod at 610HP , 590ft lbs, back 1990!
You have a right to your own opinion but not your own facts.
FACT: Jag v12 and transmission weigh in at 1100 LBS. A chev 350 with 700R4 weighs in at 700lbs You can easily shave off 100LBS with a Alu intake and heads so with the right parts the chevy is almost 1/2 the weight.
What exactly is "V12 money"
FACT: XJS' with proper conversions routinely sell for more than a comparable V12 car. You can check ebay's sold history to verify. Today I observed two similar XJS', both mid 80's models with similar high mileage, the Chevy convert sold for 50$ shy of twice the price of the v12.
FACT: Both engines have been successfully raced, both are cast iron cylinders with aluminium pistons and this would suggest a similar expected life span when properly maintained.....but maintaining a V12 is expensive and difficult when compared to a 350 so often maintenance is differed out of frugality or ignorance. In the real world you can find many Chevy engines still going with well over 100,000 miles, relatively few XJS' make it that far for a variety of reasons. BTW, chevys' dont drop valve seats.
FACT
The stroke on a Chevy 350 is 3 &1/2 inches to the Jaguar’s 2.75 inches. The rod length on a Chevy is 5.7 inches while the Jaguar is 7.125
what does that mean? At 100,000 miles the Chevy will have a measurable ridge while the Jaguar will still be in spec. ( less angularity and slower piston speed.)
chevy rod journals are 2.100 Jaguar is 2.300 Chevy crankshafts are cast Iron and weigh 27 poundsJaguar is en 40 forged steel. And weigh 78 pounds. What does that mean;
Jaguar crank shaft is much much stronger
Chevy rods are cast Jaguar rods are forged steel.
Chevy cylinders are cast into their cast iron block. overbore is only cure for wear or damage.
Jaguar cylinders are removable sleeves. ( and wear much less than their Chevy counterpart.)
Chevy has adjacent cylinders firing from 90 to 270 degrees which produces a second order harmonic that no amount of balancing will eliminate
Jaguar with its even 60 degree firing can balance a coin on a running engine.
Typical Corvette horsepower of the mid 70’s through mid 80’s 160 SAE net or 157 DIN
JAGUAR of the same period 262 -299
Both are 4 stroke models and work under the same principle one has 4 more cylinders. For those who can’t count past 10 without removing their shoes Jaguar even makes them 1 - 6 side A& B
Ah... back to the V8 / v12 and American Pushrod Iron block Chevy debate... this time with a technical twist with the concept of Rod Journal size, piston speed and rod angularity thrown in just to make it interesting. You forgot to mention how terrible the SBC oil pump design and pick up system is...lol. No doubt the V12 is technically more interesting in many ways but you and others dont get the allure of the simple elegance of the SBC. The SBC and newer LS platforms have been built as desired to the delight of hot rodders and tinker types for generations. Simple, reliable, powerful and there's an SBC for every budget. There is something special about ubiquity and few people give a darn about piston speed and rod angularity.
By 1979 the Corvette was up to 195 HP, the L82 version was 225. In 1984 emissions regulation bit and the 1984 the Corvette was back down to 205HP. But in 1985 TPI hit was installed and was backup up to 245. Then past 300 in 1993. Even at the darkest point in 1976 it was 180 HP and not the 160 HP you claim. In the mid 70's, everyone knew as soon as you got the corvette home, you could replace the carburetor and advance the timing for considerable more HP. You could even swap in a larger camshaft over the weekend with a friend. That's what Corvette was all about at the time and no-one was doing that with a Jaguar so the comparisons are pointless. Corvette is still going and evolving even with it's 16 archaic push-rods. The V12 is dead, Few manufactures still make one.
There is a major advantage to higher piston speeds, it's peak torque earlier in the RPM range where it's usable. Piston speed is what makes the SBC so powerful and high piston speed is great for making power at reasonable RPM with a mild cams. Here's how it goes... For any given RPM...The valve begins to open and as that piston crests TDC it then begins it's decent at an accelerating rate sucking in copious amount of Air and fuel. This is where high piston speed is a huge benefit, moving air. So power is more immediate and more direct at lower RPM where it's usable.
As for rod journal size and crank weight... This is why the Jaguar V12 is such a disappointing compromise and was unfinished and contradictory in a lot of ways. With the V12 we have a large journal heavy crank with a short stroke. The heavy crank and large journals are not good for high RPM and but the short stroke/large bore favors high RPM. That's a contradiction. Absolutely no need for a Forged V12 crank for 300HP as cast crank would have sufficed. Jag should have saved a bundle and cast the crank and put the monies saved into the heads. That's what Ford did in early 90's , thus greatly improving the last of the Jaguar V12's.
Why compare a Corvette to an XJS,? They are different cars with different purposes and the Corvette always performed better in every measurable way on and off the track even with less HP.
.
Did you ever weigh a ribbed stamped steel valve cover? Far lighter and stronger than it's cast Aluminum counter part. That's elegant design with in-elegant materials.
All cross plane V8's have the adjacent cylinder problem not just chevy's but as a practical matter it's not significant. . Starting in the early 90's precision balancing and revised firing orders helped the moden V8 attain V12 smoothness. Lexus made a spectacle of it with there V8 in the 90's doing the wine glass balance trick. See this vid...
V12's tend to get grumbly as they age in mileage. Bank to bank timing differences begin to appear as timing chain stretch makes one side advance and the other side retard valve events. This phenomenon is less evident on the earlier Jag V12 becasue of it's central timing and non-existent on a cam-in-block push-rod V8.
Yes there were some dark days for the SBC and most other engines in the 70's but in the 50's and 60's they made more HP than the Jag V12 and by the early 90's they surpassed the V12's HP on paper too I'm not so sure the V12 was making all the HP Jaguar claimed it was in the 70's... have you ever drive one of those late 70's to early 80's Fuel injected V12's? They're slugs and I'm inclined to think Jags quoted HP figures were optimistic. Also Corvette had an interests in low HP figures for Insurance reasons at the time. Really silly to compare them.
You've got a clear case of VXIIDS. Pronounced vix-citis Or 'V12 Dillusion Syndrome' More specicifically JVXIIDS or 'Jaguar V12 Dillusional Syndrome'. Pronounces Ja-Vix-citis. There's only one cure...Build a your own V12 and then race a built Chevy V8 on the track. When you get passed over and over again you will long for the sound of your own V8 going full song at WOT through long tube headers. If you have already been exposed to this treatment try upping the rapidity of your dose.
BTW...Do us all a favor and stop replying to 10 year old threads. Your ramblings are old news, inaccurate, pointless and are just soiling an already cluttered inter-web.
Last edited by icsamerica; Sep 13, 2019 at 10:02 AM.
No doubt the V12 is technically more interesting in many ways but you and others dont get the allure of the simple elegance of the SBC.
The SBC and newer LS platforms have been built as desired to the delight of hot rodders and tinkers for generations. Simple, reliable, powerful and there's an SBC for every budget. There is something special about ubiquity and few people give a darn about piston speed and rod angularity.
Yup!.
As you know I'm a V12 devotee but, still, I regard the Jag V12 as more of a novelty item than anything else....very much like Jaguar cars themselves. Magnificent in some respects yet a letdown in others.
Whether we're talking about a Jaguar car, a Jaguar engine , a Corvette, or an SBC ....we love it for what it is, not for what it isn't.
This article from PM in 1984 is one of my favorites as a car guy. They actually do compare the XJS to a Corvette on the track and it did fairly well for a cushy GT. When I read this I couldn't help Imagine how great an XJS with a 5 speed, a rear sway bar, sport dampers and some brake cooling ducts. Full magazine here. A few years ago I built one with a 6 speed, rear sway bar, and 6.0 V12 and it did race at Lime Rock. You can see it race here, skip adhead to 5:23 when things get going.
swapped 4 XJS's. Did one big block.. (bad idea).
Cant beat it as a everyday driver and it does everything better. Including the sound. Only regret is that I didnt use an LS. Will remedy that soon.
This article from PM in 1984 is one of my favorites as a car guy. They actually do compare the XJS to a Corvette on the track and it did fairly well for a cushy GT. When I read this I couldn't help Imagine how great an XJS with a 5 speed, a rear sway bar, sport dampers and some brake cooling ducts. Full magazine here. A few years ago I built one with a 6 speed, rear sway bar, and 6.0 V12 and it did race at Lime Rock. You can see it race here, skip adhead to 5:23 when things get going.
Doesn't sound to me like Mr Posey thought very much of the "Fabled" Corvette.
Certainly not... the '84 Vette was a terrible vehicle, it was built to a price and date. Chevy wanted it to be able to attain 1.0G on the skid pad and rushed it to market becasue of the fear of impending regulations . To do 1,0G on the skip pad on the 16 tires technology of the day they needed to be a special hard design and the suspension needed to be super stiff. The 1984 Corvette in the test had the Z51 suspension package which had far stiffer springs and dampers than the base model. Most 84 Vette's were sold with the Z51 package becasue there was great fan fair for the C4 at the time. The C4 was considered Revolutionary at the time much like the C8 is today. Now-a-days the early C4's are considered Junk. I had a 1985 Z51 Corvette which had the the 1984's base Corvette suspension and it was punishingly stiff. The stiff spring rates combined with the flexibility of the Targa style top made the car a creaky flexible mess of an Automobile. In 85 the softer base suspension, engine torque and throttle of the new TPI intake made the car a bit less creaky and fun to drive non-the less.
In many ways I wish this test was redone in 1985 becasue Porsche released an upgraded 928S in 1985 with it's new 4 cam engine and far better transmission. Chevy also resigned the Corvette and dialed down the suspension and upped the power drastically. Last time I was at Limerock in June '19 there was a mostly stock 1987 C4 Corvette with a mild cam swap (270HP) and good tires that ran the track in 57 seconds.
Sadly Jaguar made few changes to the XJS until 1994. Quite frankly there Should have been a XJS-S in the early 80's with a manual transmission, up-rated suspension, thicker, sway bars front and rear, and no chrome like the original in 1976. It may not have sold well but it would have done a lot for Jaguar's Sporting image in the long run. This is an image they are still trying to claw back today.
Last edited by icsamerica; Sep 14, 2019 at 01:47 PM.
Back in my dealership days we used to refer to Corvettes as "15 minute cars". That is, they were fun to drive for about 15 minutes and then you've had enough.
I really like Corvettes, broadly speaking. But they come in a lot of different flavors and some are better than others.
By the early 90s the C4 series was much improved, IMO. I'm kicking around the idea of buying one while the prices are still low.
I enjoyed the comparo article. The editors were more kind to Jaguar than usual .
Not so much now, perhaps, but back in the day the Jaguar guys always leaned towards comfort rather than performance. That is, if a decision had to be made to give more performance or more comfort, they always leaned towards 'more comfort'. Thus Jaguars often didn't fare well compared to the more raw-edged competitors.
