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maybe so but not on this J/F forum , TWR and the USA jaguar engines did after spending over million dollars!
b y that era a POSITIVE PRESSURE in the inlet manifolds(supercharging changed everything). i have read maybe 1000HP?
hey we even have 4 cylinder engines with more than 400HP today!
im sad to say the day for Jag V12s in the HP wars is past, not sayin cant be done (just not worth the effort/MONEY)!
maybe so but not on this J/F forum , TWR and the USA jaguar engines did after spending over million dollars!
b y that era a POSITIVE PRESSURE in the inlet manifolds(supercharging changed everything). i have read maybe 1000HP?
hey we even have 4 cylinder engines with more than 400HP today!
im sad to say the day for Jag V12s in the HP wars is past, not sayin cant be done (just not worth the effort/MONEY)!
100% correct. and its not just the HP output that needs to be upgraded, think suspension brakes etc to handle that amount.
You want lots of power the most efficient way is to lump it.
or add a 150 shot of nitrious to it lol.
me personally im reaching for 300hp and 300 ft/lbs lol
Took apart the relays mounted on radiator support and soaked the housings in phosphoric acid, sanded the internal contact and then reassembled them. I also moved the horn relay from its inscrutably located position buried down low on the right side of the engine bay up high to the proper relay location (did this cause my horn didn’t work initially after reattaching wires and I refused to trouble shoot laying on my back reaching up into the engine bay.
I've heard more than a few non-American car guys poking fun at the massive displacement and low power output US cars back years ago (looking at you Jeremy Clarkson),
I've found it useful to remind them of the 6 liters it took the Brits to find 300hp from a v12.
I've heard more than a few non-American car guys poking fun at the massive displacement and low power output US cars back years ago (looking at you Jeremy Clarkson),
I've found it useful to remind them of the 6 liters it took the Brits to find 300hp from a v12.
the goal of the XJS wasn’t peak power. it was elegant power. Yet peak power for the time was remarkable well ahead of the Americans.
Do remember that up until 1973 horsepower numbers were not real!! They were a function of marketing and imagination. If 350 horsepower out of 350 cu in. Had marketing decided, then so it was advertised.
.
I could kinda buy that in the late 70's and into the 80's when nobody was making power, but Mercedes was comfortably past 300 with a 5L v8 by 90. They were plenty elegant unless you floored it.
Of course you paid for that level of engineering chops.
They finally hit 300 in the mid 90's with the later injection on the 6L I believe? The ole 350 chevy was up to 300 by then, or 400 with
the fancy cams one. My assumption is that Jaguar just didn't have the money to keep up with development.
And the gross/net isn't really worth discussing for domestic stuff, they underrated many of them for various comical reasons(Chrysler seemed to do that with nearly everything in the good ole days).
There were plenty of 300+ hp 350's in the early 70's before they had to figure out how to meet smog standards and mpg requirements.
Even the non-smog early 70's E-Type v12 didn't make more but rather "different" power than the six of the day, and that was still sub 300 and I've always been told the v12 wasn't very
popular with the Jag crowd back then. It just doesn't seem like a very efficient motor. Beautiful, interesting, unique, but it seems to ask a lot for what it delivers.
I've always thought Jaguar six's were better motors all in all.
And that's all perfectly okay, just interesting to observe and ponder.
I grew up racing that early six. The killer in it was the long (4.17 ) stroke which at red line (5500) had piston speed of a Chevy small block at 7500 rpm (remember each piston goes from a dead stop up to a dead stop down).
With the original 5.3 liter V12 (which was originally designed to go out to 8 liters). The piston stroke is unbelievably short (2.750 ) which allows 8000 rpm with piston speeds suitable for cast pistons. Cast pistons are better for production engines since they don’t expand like forged pistons do producing an unacceptable knock until they warm up.
The V12 simply wasn’t developed as much as the early cast iron 6 cylinder. Sir William went deeply in debt to produce that engine very much on the cheap. Using a lot of the same equipment as the 6 cylinder used.
Remarkably the V12 is 30 pounds lighter then the 4.2 six cylinder. Plus it’s really beautifully designed and built. For example the crankshaft is forged out of EN30 steel ( very high grade ) and once all the machining is done it is heat treated to racing standards. The crankshaft alone weighs 78.8 pounds. Nearly Three times what a Chevy 350 crank weighs and twice what a 454 weighs. ( most of those are cast iron)
The block isn’t a cast aluminum block. It’s a die cast. Producing no air pockets or casting flaws. And far superior grain orientation. In addition the studs holding the heads on (54) go all the way into the crank webs. The mains have either 4 or 6 studs.
If you are familiar with the engine blocks in a top fuel dragster making thousands and thousands of horsepower nothing in that engine block will surprise you but compared to ordinary production blocks this is a world different!!
In short this same engine is built like a formula 1 engine regarding strength and quality of components
Power? Apples and oranges. The 4.2 engine made 265 horsepower but the last 65+ horsepower was pure advertising. ( or ponies with really skinny legs.) Prior to 1973 horsepower had no real standard. After 1973 ( and all XKE V12’s ) Horsepower for the V12 was listed as 237. DIN as installed. ( which is 1.1% more powerful than SAE horsepower)
In comparison the Chevy 350 was 160 SAE Net horsepower. And the 454 was 230 SAENet horsepower. So making more power than a 454 engine did. On a 128 cubic inches less is impressive.
Remember the Chevy typically was geared for a top speed less than 120 mph. While an XKE would go 150 mph.
I've heard more than a few non-American car guys poking fun at the massive displacement and low power output US cars back years ago (looking at you Jeremy Clarkson),
I've found it useful to remind them of the 6 liters it took the Brits to find 300hp from a v12.
and don't forget, all muscle cars from back in the day (60's up to around 70), they were all very much under rated on the HP
They finally hit 300 in the mid 90's with the later injection on the 6L I believe? .
The European market V12 was 299hp in 1982. At the time the XJS was the fastest car you could buy with an automatic transmission.
For the US market, the V12 had 262hp. Sticker price then was $34,000, for comparison the Mercedes 380SEC coupe was 155hp and cost $53,570 and the BWM 633CSI was 181hp and cost $39,120. The Jaguar was the performance bargain then.
and don't forget, all muscle cars from back in the day (60's up to around 70), they were all very much under rated on the HP
Be very careful of words like all. First stating that means major corporations were willing to falsify documents to slightly increase sales. Just not possible. They all have corporate lawyers.
The “underrated” only involved a tiny handful of the most powerful engines. Those are highly prized and sell for an extreme premium.
Most engines were lower compression, hydraulic lifter, with smaller valves etc. often with either a single 4 barrel carb or a two barrel carb.
The power given was not as actually installed which all later ratings are. They were optimized on the engine dyno and do not reflect the power used to operate accessories and all post 1973 engines are rated at.
In fact the numbers used on those few “underrated” engines were actual dyno numbers. Or perhaps less “enhanced numbers”.
Be very careful of words like all. First stating that means major corporations were willing to falsify documents to slightly increase sales. Just not possible. They all have corporate lawyers.
The “underrated” only involved a tiny handful of the most powerful engines. Those are highly prized and sell for an extreme premium.
Most engines were lower compression, hydraulic lifter, with smaller valves etc. often with either a single 4 barrel carb or a two barrel carb.
The power given was not as actually installed which all later ratings are. They were optimized on the engine dyno and do not reflect the power used to operate accessories and all post 1973 engines are rated at.
In fact the numbers used on those few “underrated” engines were actual dyno numbers. Or perhaps less “enhanced numbers”.
Lots of correct restoration and original engines have been dyno'd over the decades, there were quite a few that were under-advertised. Chrysler especially seemed to really like to do that for some reason.
There's lots of urban legend type stuff but it's been fairly well proven to have been the case for whatever reason.
None of the pedestrian models of course, but the performance stuff. And they weren't all that special really with the exception of moon shot stuff like hemi's and SOHC fords and what have you,
little compression, a cam of some note, enough intake and exhaust and just like today with
a run of the mill v8 you've got 300, 400hp with little effort. That all went to pot after 72 or so when nobody in the US could make any power and pass smog.
Heck oldsmobile had well over 300hp from a 394ci v8 by the mid 60's. And even with adding accessories and driveline losses that's still a good 300 at the wheel.
Things only improved from there until the malaise set in.
I think that might be the point, anyone that can read a plastigauge and has a credit card and a summit racing catalog can take a 70's, 80's, 90's v8 from
anyone and have a reliable 400hp without really trying. I learned early on that you really can't do that with European stuff in general, and especially
not with the Jaguar v12. Which is, a v12, not a six, not an eight, it's a v12 and there's some expectations there that it just isn't meeting unless you
have a TON of knowledge, experience, and money to put into it. It compared much more favorably performance wise in the 70's and 80's but it hasn't
aged particularly well regarding performance.
It's still a fascinating and beautiful engine though. But you can (and people often do) replace it with any number of alternatives from the last couple decades because they just work better,
and the cassis doesn't argue with you too much about it like some do.
I grew up racing that early six. The killer in it was the long (4.17 ) stroke which at red line (5500) had piston speed of a Chevy small block at 7500 rpm (remember each piston goes from a dead stop up to a dead stop down).
With the original 5.3 liter V12 (which was originally designed to go out to 8 liters). The piston stroke is unbelievably short (2.750 ) which allows 8000 rpm with piston speeds suitable for cast pistons. Cast pistons are better for production engines since they don’t expand like forged pistons do producing an unacceptable knock until they warm up.
The V12 simply wasn’t developed as much as the early cast iron 6 cylinder. Sir William went deeply in debt to produce that engine very much on the cheap. Using a lot of the same equipment as the 6 cylinder used.
Remarkably the V12 is 30 pounds lighter then the 4.2 six cylinder. Plus it’s really beautifully designed and built. For example the crankshaft is forged out of EN30 steel ( very high grade ) and once all the machining is done it is heat treated to racing standards. The crankshaft alone weighs 78.8 pounds. Nearly Three times what a Chevy 350 crank weighs and twice what a 454 weighs. ( most of those are cast iron)
The block isn’t a cast aluminum block. It’s a die cast. Producing no air pockets or casting flaws. And far superior grain orientation. In addition the studs holding the heads on (54) go all the way into the crank webs. The mains have either 4 or 6 studs.
If you are familiar with the engine blocks in a top fuel dragster making thousands and thousands of horsepower nothing in that engine block will surprise you but compared to ordinary production blocks this is a world different!!
In short this same engine is built like a formula 1 engine regarding strength and quality of components
Power? Apples and oranges. The 4.2 engine made 265 horsepower but the last 65+ horsepower was pure advertising. ( or ponies with really skinny legs.) Prior to 1973 horsepower had no real standard. After 1973 ( and all XKE V12’s ) Horsepower for the V12 was listed as 237. DIN as installed. ( which is 1.1% more powerful than SAE horsepower)
In comparison the Chevy 350 was 160 SAE Net horsepower. And the 454 was 230 SAENet horsepower. So making more power than a 454 engine did. On a 128 cubic inches less is impressive.
Remember the Chevy typically was geared for a top speed less than 120 mph. While an XKE would go 150 mph.
They really are pretty and interesting engines, and heavy. Impressively heavy.
Light is expensive though I guess.
The European market V12 was 299hp in 1982. At the time the XJS was the fastest car you could buy with an automatic transmission.
For the US market, the V12 had 262hp. Sticker price then was $34,000, for comparison the Mercedes 380SEC coupe was 155hp and cost $53,570 and the BWM 633CSI was 181hp and cost $39,120. The Jaguar was the performance bargain then.
They really are pretty and interesting engines, and heavy. Impressively heavy.
Light is expensive though I guess.
remember Sir William Lyons built it to go out past 500 cubic inches.
At 700 pounds it’s heavy as a 326 cubic inch engine. About 300 pounds too heavy. But at 500 cu inches it’ would be very typical.
The original 5.0 V12 weighed 200 pounds less while making 502 horsepower. But it was designed as a race motor not a luxury motor.
The benefits of a V12 over a V8 of the same size. More torque, more power, smoother running. ( all V8’s have a 2nd order harmonic that results in much greater vibration).
The cast Iron V8 engines in Chevy’s were lighter. But not as well built. Remember I love Chevy’s and have bought 22 new Chevy’s over my lifetime, plus 6 used.
Because they are so common a lot of people learned how to fix them.
But not so many once EFI became common!
When it did the dealer was about the only place they could be fixed. Until the late 1990’s with OBD2 which you could plug in a tester and find out what was wrong.
Jaguar got OBD2 at the same time. After production of the V12 was over.
01-25-2023, 04:27 PM
