[xj-s] Max RPM on V-12

Kirbert wrote:

Still won’t hurt the engine, though! The engine could stand 8000,

Not doubting you Kirby, but what is your source for this? Question: If
the fuel delivery system and air intake were up to the task, what harm is
there in running over redline on the “street” tach?

The red line is there from the factory for a reason. I do know that due
to the overly square bore/stroke of this engine that it was designed to
rev to 10,000 (or more I think) RPMs, but that I would assume would
require with tougher internal components (crank, conn rods, valve springs,
etc.)

World Peace Through British Cars

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

Wayne: I haved reved my 83 to around 9500, and when it was running I
turned it 8500 all the time, but it was setup to do so.
If I ever get around to building the race engine I plan to turn it in
the 12,000 range.
Chad Bolles Jaguar Performance, LLC 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

Wayne Estrada wrote:>

Kirbert wrote:

Still won’t hurt the engine, though! The engine could stand 8000,

Not doubting you Kirby, but what is your source for this? Question: If
the fuel delivery system and air intake were up to the task, what harm is
there in running over redline on the “street” tach?

The red line is there from the factory for a reason. I do know that due
to the overly square bore/stroke of this engine that it was designed to
rev to 10,000 (or more I think) RPMs, but that I would assume would
require with tougher internal components (crank, conn rods, valve r

Still won’t hurt the engine, though! The engine could stand 8000,

Not doubting you Kirby, but what is your source for this?

Roger Bywater, who worked in the engine development section at Jaguar
while this engine was being developed, and who knows people who have
actually raced largely-stock V12’s using 8000 as a redline.

Question:
If the fuel delivery system and air intake were up to the task, what
harm is there in running over redline on the “street” tach?

The fuel delivery system is more than up to the task, and the air
intake is only restricted by the little horns on the air filter
housings – easily remedied. The fact that the engine runs outta
power around 7000 is a DELIBERATE feature of the fuel mapping, to
prevent damage. If you wanna rev higher, you merely need a remapped
ECU. Contact – you guessed it, Roger Bywater at AJ6 Engineering.

The red line is there from the factory for a reason.

Redlines can fool people. Racers think they’re the point where the
engine comes apart, but manufacturers think of them as the point
where the car will run until the warranty period is up. In the case
of the Jag V12, apparently the biggest problem above – or even a bit
below – 6500 is the torque convertor, a GM product intended for 5000
rpm engines.

I do know that
due to the overly square bore/stroke of this engine that it was
designed to rev to 10,000 (or more I think) RPMs, but that I would
assume would require with tougher internal components (crank, conn
rods, valve springs, etc.)

I’m not sure what. It looks like Jag put just about all the goodies
into the road car, with the possible exception of the pistons
themselves – which appaear to have some concessions to quiet and
durability over performance, although I dunno anyone who’s had one
come apart.

– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979From: Wayne Estrada wayne@richmond.net

Kirbert wrote:

I’m not sure what. It looks like Jag put just about all the goodies

into the road car, with the possible exception of the pistons
themselves – which appaear to have some concessions to quiet and
durability over performance, although I dunno anyone who’s had one
come apart.

Funny you mention that…I read (somewhere) that the pistons are about as
fine as you’ll find anywhere. I don’t know about weight considerations
for piston ft/min, but excellent design supposedly.

Still a little concerned about the GM400 and valve float with the stock
springs. Any Hydromatic 400 experts outs there regarding max RPM for this
tranny? I’ve only touched a tad over red line a few times…not much more
power (with current set up) so not worth the risk.

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

Wayne

The transmission problem is primarily the OEM torque converter which tends to
go ballistic at speeds >7K. The whole business can be beefed up though; I’m
told sufficiently to withstand speeds of 10K RPM. They do it for drag racing,
so it’s likely possible – of course reliability isn’t exactly a big issue
there.

Emile

'93 XJR-S
'95 XJS 4.0
'96 XJR

Wayne Estrada wrote:> Kirbert wrote:

I’m not sure what. It looks like Jag put just about all the goodies

into the road car, with the possible exception of the pistons
themselves – which appaear to have some concessions to quiet and
durability over performance, although I dunno anyone who’s had one
come apart.

Funny you mention that…I read (somewhere) that the pistons are about as
fine as you’ll find anywhere. I don’t know about weight considerations
for piston ft/min, but excellent design supposedly.

Still a little concerned about the GM400 and valve float with the stock
springs. Any Hydromatic 400 experts outs there regarding max RPM for this
tranny? I’ve only touched a tad over red line a few times…not much more
power (with current set up) so not worth the risk.

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

Funny you mention that…I read (somewhere) that the pistons are about
as fine as you’ll find anywhere. I don’t know about weight
considerations for piston ft/min, but excellent design supposedly.

That’s because I wrote it in the Book! And they are just about the
most advanced design you’re gonna find in a production automobile –
it’s just that the objective may have had noise and durability thrown
in, while the racer would only be concerned about redline.

Still a little concerned about the GM400 and valve float with the
stock springs. Any Hydromatic 400 experts outs there regarding max
RPM for this tranny? I’ve only touched a tad over red line a few
times…not much more power (with current set up) so not worth the
risk.

Bywater suggests that the first fix would be to replace the torque
convertor with a “furnace-brazed” model. I believe that furnace
brazing, as opposed to simple welding used on the OEM item,
eliminates the weakness of the welds and may also permit the use of a
stronger/harder steel alloy for the torque convertor. Whatever, it
shouldn’t be difficult at all to find high-performance torque
convertors for a GM400 if you’re gonna go past 6500.

I dunno if anyone has experienced a problem with valve float on this
engine. That is the advantage of the direct-acting OHC layout, after
all – much less reciprocating mass in the valvetrain, so much less
tendency to float. The OEM springs certainly don’t seem very stiff
to me, but the engine doesn’t display any symptoms of float up to the
6500 rpm redline.

– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979From: Wayne Estrada wayne@richmond.net

Emile Desroches wrote:> The transmission problem is primarily the OEM torque converter which tends to

go ballistic at speeds >7K. The whole business can be beefed up though; I’m
told sufficiently to withstand speeds of 10K RPM. They do it for drag racing

Yes they do. The TH400 is one tough guy. Is the torque converter the only hang
up in this scenario?

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

Kirby,

What are the symptoms of valve float?

Peyton Gill

The OEM springs certainly don’t seem very stiff
to me, but the engine doesn’t display any symptoms of float up to the
6500 rpm redline.

– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979

Wayne: I haved reved my 83 to around 9500, and when it was running I
turned it 8500 all the time, but it was setup to do so.
If I ever get around to building the race engine I plan to turn it in
the 12,000 range.
Chad Bolles Jaguar Performance, LLC 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

I once talked to a ex-british jag guy (owns ex jackie stewart xj-s, an S3 xk-e &
an xk120), who was involved in a racing enterprise during the early '80s.
Apparently they coudln’t reliably break into 5 figures, due to the timing chain
giving up the ghost. They even tried triple row chain without any luck.On Wed, 19 Jan 2000, you wrote:

Tony: He must have been drinking when they worked on the V12. Group 44
ran their engines all the time in the 7000 range and when pushed would
go to 7500-8000.
TWR(who won LaMans) also used the same rpm range and used the std two
row chain.
Chad Bolles Jaguar Performance,LLC 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

Tony Bryant wrote:>

On Wed, 19 Jan 2000, you wrote:

Wayne: I haved reved my 83 to around 9500, and when it was running I
turned it 8500 all the time, but it was setup to do so.
If I ever get around to building the race engine I plan to turn it in
the 12,000 range.
Chad Bolles Jaguar Performance, LLC 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

I once talked to a ex-british jag guy (owns ex jackie stewart xj-s, an S3 xk-e &
an xk120), who was involved in a racing enterprise during the early '80s.
Apparently they coudln’t reliably break into 5 figures, due to the timing chain
giving up the ghost. They even tried triple row chain without any luck.

Chad Bolles wrote:

Tony: He must have been drinking when they worked on the V12. Group 44
ran their engines all the time in the 7000 range and when pushed would
go to 7500-8000.
TWR(who won LeMans) also used the same rpm range and used the std two
row chain.

I have zero experience with racing engines, but I thought this “type” of engine would
red line in the 10-12K range. My (then new) 1972 Datsun 240Z redlined at 7,500, and
its about half the XJS V-12 (single Overhead Cam). I always thought redline was more
a factor of piston weight/connecting rod strength (with some strong bearings and
crank). Someone please enlighten me.

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

Chad Bolles wrote:

Wayne: I used to drag race a 426 Dodge Hemi. It was destroked to 405
cuin and I would turn it, usually 10,000 at the line. Once in awhile it
would rev to 10,300, but when it did it would bend an intake valve.
The piston/rod assy in this engine weighs a TON, compared to the Jag V12
stuff. Like you said you need super rods and pistons to turn revs like
that and that is what I used in the Hemi, also use stuff like that in my
V12.

Thanks as always. I guess to re-phrase the question, "How far can a STOCK jaguar 5.3 V-12
rev without damaging the engine?

Partial answer is not based on testasarone (?), but ‘the need for speed’. With the AJ6
ECU, throttle bodies and revised dual intake low restriction air filters, my car pulls
strongly to red line of 6500/6600, where power would dramatically drop off after 5300
before (i.e. not worth the effort beyond that range), and I believe the stock power curves
show that.

As we all know, its not the max revs that’s important, but where the engine hits its max HP
and torque figures. Oh well, more goofing off in the office when I should be working!

Wayne Estrada
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas Sedan (Alpine Green)
Richmond VA, USA
http://www.u3training.com/jaguar

My '72 240Z had a redline of 6500, but it was a complete waste of time to rev
it beyond 6000 as it fell flat on its face beyond that. (To answer the
obvious comments to come: The car was faster short shifting it and starting
lower in the power band then if you waited for it to claw its way up to
redline before shifting)

Nissan tried to copy the E-Type interiors (which is why it somewhat resembles
our cars interior) in the 240Z’s.

As I understand it, connecting rods and the like can be a problem in very
high RPM applications, but the valve train speed is generally a limiting
factor in the motor. The motor in our toys is probably more able to take
high RPM’s than the air-conditioning compressors, alternators, and
transmission. You might be able to run the big motor up to high RPM’s, but
durability of it and the auxiliary drive systems would probably not be
something you want to test in your personal vehicle.

Just my unasked for opinion.

Douglas Dahl
1989 12 cylinder toy (91,800 miles)