Guess who ALSO has a problem with plastic:http://www.jcna.com/library/tech/tech0028.html
"When the tensioner fails the chain slack may allow the chain to jump one tooth on a sprocket and then the exhaust valves open and close later than normal. Performance will suffer. But if the chain jumps two teeth or more the rising piston at the end of the exhaust stroke hits the exhaust valve which is still open, and that instantly is the end of your engine. Tooth jumping happens especially as the engine kicks into life when you start it.Jaguar has redesigned the secondary tensioner 3 times since V8 introduction. Technical Bulletin 303-30 dated 12-98 recognizes a rattling noise caused by tensioners at cold start and notes a revised design with noise dampener clip added. This change commenced with engine No. 98102106XX and will be installed on earlier engines under warranty. If your engine qualifies - and you do have that noise, right? - you might try the warranty road. Engine numbers are on the upper front of the engine and apparently require removal of the center plastic cover to be seen.
Paul Skilleter of Jaguar World Monthly replied, "It appears that failures of the sort described occur only at relatively high mileages (probably beyond the 70,000 mentioned), and then only after the engine has been noisy for some while."
Jag V8 chain tensioner problem
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maxnix
- Posts: 22627
- Joined: Mon Jul 22, 2002 8:11 pm
- Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45
From http://www.jagweb.com/aj6eng/v8_performance.html :
"It is perhaps then not surprising that on the Jaguar V8 the tensioners on the secondary camshaft chains in particular have developed a reputation for being troublesome. In fact it may not be that there is any weakness in the tensioners themselves, rather that at certain critical speeds heavy torque reversals on the chain can produce higher than expected stab loads, a condition which can probably be exacerbated by some usage patterns. It is perhaps interesting that the later 4.2 V8 uses more rugged morse internal tooth primary chains and that when BMW introduced a similar V8 (four valve, twin OHC, Nikasil bores, sintered fracture split con-rods) in 1992 they used duplex chains throughout. Whilst Jaguar's design team, in choosing a single link chain drive, did specify that it should be rated for heavy duty, one wonders if there have been any regrets that space wasn't made to use a duplex chain rather than relying on the lightweight valve gear to let them get away with the narrower option?"
It includes an interesting comment on high sulfur fuels and Nikasil liners?"With the benefit of hindsight the decision to use Nikasil plated cylinder bores instead of conventional liners might be judged a bad mistake, but it is one that was understandable and which caught BMW off-guard as well. The Nikasil process had been used for years on motorcycle engines and is in common use for F1 and other racing engines so it is hardly unproven technology. At the time BMW's exceptionally tight control of oil on the bores was thought to be a factor in their troubles, which would not apply elsewhere. In truth, instances of failure of the Nikasil coating appear to have been induced by poor fuel quality in certain markets allied to short journey usage, and engines running on low sulphur fuel would be most unlikely to suffer the problem. Jaguar resolved service failures in an honourable fashion but eventually decided to abandon Nikasil and revert to conventional cast iron liners (from VIN 42776 XK8, 878718 XJ8). The advantages of light weight and close running clearances were sadly lost. Ironically the fuels which caused the problem have now virtually disappeared from the market."
And an interesting comment on the XJ8R supercharger set-up:"The supercharged V8 is an impressive performer yet flow through the intercoolers is a little constricted and the Eaton roots supercharger is not very efficient, so it could have been even better. For example, a more efficient screw type of supercharger would provide an immediate gain of around 40 b.h.p. and would make possible quite a lot more than that. Anyone interested in a more detailed explanation of why might care to read the feature about supercharging technicalities found elsewhere on this website."
And a cautionary note on why stroked motors are cheap ways to power, but not always desirable for long term durability:"The size increase to 4.2 litres was obtained by increasing the stroke - always a favoured approach at Jaguar - necessitating the crankpin journals to be reduced in diameter to maintain the same block height."
"It is perhaps then not surprising that on the Jaguar V8 the tensioners on the secondary camshaft chains in particular have developed a reputation for being troublesome. In fact it may not be that there is any weakness in the tensioners themselves, rather that at certain critical speeds heavy torque reversals on the chain can produce higher than expected stab loads, a condition which can probably be exacerbated by some usage patterns. It is perhaps interesting that the later 4.2 V8 uses more rugged morse internal tooth primary chains and that when BMW introduced a similar V8 (four valve, twin OHC, Nikasil bores, sintered fracture split con-rods) in 1992 they used duplex chains throughout. Whilst Jaguar's design team, in choosing a single link chain drive, did specify that it should be rated for heavy duty, one wonders if there have been any regrets that space wasn't made to use a duplex chain rather than relying on the lightweight valve gear to let them get away with the narrower option?"
It includes an interesting comment on high sulfur fuels and Nikasil liners?"With the benefit of hindsight the decision to use Nikasil plated cylinder bores instead of conventional liners might be judged a bad mistake, but it is one that was understandable and which caught BMW off-guard as well. The Nikasil process had been used for years on motorcycle engines and is in common use for F1 and other racing engines so it is hardly unproven technology. At the time BMW's exceptionally tight control of oil on the bores was thought to be a factor in their troubles, which would not apply elsewhere. In truth, instances of failure of the Nikasil coating appear to have been induced by poor fuel quality in certain markets allied to short journey usage, and engines running on low sulphur fuel would be most unlikely to suffer the problem. Jaguar resolved service failures in an honourable fashion but eventually decided to abandon Nikasil and revert to conventional cast iron liners (from VIN 42776 XK8, 878718 XJ8). The advantages of light weight and close running clearances were sadly lost. Ironically the fuels which caused the problem have now virtually disappeared from the market."
And an interesting comment on the XJ8R supercharger set-up:"The supercharged V8 is an impressive performer yet flow through the intercoolers is a little constricted and the Eaton roots supercharger is not very efficient, so it could have been even better. For example, a more efficient screw type of supercharger would provide an immediate gain of around 40 b.h.p. and would make possible quite a lot more than that. Anyone interested in a more detailed explanation of why might care to read the feature about supercharging technicalities found elsewhere on this website."
And a cautionary note on why stroked motors are cheap ways to power, but not always desirable for long term durability:"The size increase to 4.2 litres was obtained by increasing the stroke - always a favoured approach at Jaguar - necessitating the crankpin journals to be reduced in diameter to maintain the same block height."
This problem affects only the 97-99 Jags as they used Nakisil lined cylinders with high sulfur gas = bad news.
http://forums1.roadfly.org/jag...fault
go to the above link .....you will see many failures with only 30K on the clock
http://forums1.roadfly.org/jag...fault
go to the above link .....you will see many failures with only 30K on the clock
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JoshIsSciFi
- Posts: 281
- Joined: Wed Mar 03, 2004 5:27 pm
- Car: 92 Q45
- Contact:
You know what I think is funny... is the people at Infiniti decided to just sit down and say "Hey, how can we screw our customers really badly..... I know... lets alert them to a plastic chain guide that can cause them to lose the engine... but.... *snickers all around*.... we won't cover it on a recall!!!"
The XJR makes flat out way less power then it should
It has an Eaton 112 blower pushing 11.6 psi.. and it only makes 370 hp, a whopping 80 more hp then a stock XJ
That's flat out weak... Driven an XJR extensively.. it's nice, but it's high rpm performance isn't up to par.. It should be much faster.
We are looking at 400+ hp with a measely 6 psi
It has an Eaton 112 blower pushing 11.6 psi.. and it only makes 370 hp, a whopping 80 more hp then a stock XJ
That's flat out weak... Driven an XJR extensively.. it's nice, but it's high rpm performance isn't up to par.. It should be much faster.
We are looking at 400+ hp with a measely 6 psi
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450sxtc
- Posts: 364
- Joined: Sun Jun 13, 2004 8:28 am
- Car: 95 pearl vq'd s14 SE, 96 red s14 SE, 88 Rx-7 GXL, 90 GXL, 03 G35 Sedan, parting 91 q45
or..........................a few of us could put our heads together and try to come up with a rolling tensioner (aftermarket). I think if it worked, even nissan might buy it.....couldn't be THAT hard to fab something up and if no everyone else is scared to try it on their motor, then I'll try it b/c mine isn't an interference motor anymore. Furthurmore, I was trying to think up a way to convert this motor to belt drive (a heck of a lot of machining work) so that it WOULD have a rolling tensioner. It can be done. They do it on SBC's. There's probaly not a huge market for it but there would be after people started catching on to how much stronger something like that could make these motors.
911/Q45 wrote:What's the girl with the golf club think about that?
That photo is a year old taken back in Spokane WA. I'm not with the girl with the golf club -- she asked me to move with her to Arizona where she had a soccer scholarship offer, I chose a free education at a private university and moved to St Louis instead. I win!
And shes jewish by the way.
Man LOOK AT THAT AMAZING SHINE! God I love TR-3.
-Jesda
zinkie13.....congrats on the new jag. I don't know if you are already aware of this jag forum below....but click on the link as it is the single best source for XK8 & XJ8 owners as they have 2-3 actual dealer mechanics on the board helping owners out with problems on there cars.....one of the problems you might have next is the throttle body that causes stalling at highway speeds, hesitation on acceleration, etc......the XKR is my new toy within the next year so I have been following the board closely on what the problems and issues are with the cars
http://forums1.roadfly.org/jaguar/forums/xk8/
http://forums1.roadfly.org/jaguar/forums/xk8/