Perhaps a silly question but interesting

Has anyone rev’ed their engine over 6grand? If so what did you take from that and what happended? How many times and how often? Around 2012 I took mine in 3rd gear to 125mph, up and down about four times to see if I could do an ‘Italian Tune up’ and it did improve the performance overall. Never been higher than that. It gets a little scary at those levels. Fords and Chevys doing almost 4grand is easy. And yes, I have spun bearings on Chevys and Oldses. I was in my 20’s back then.

I have 97K on my Jag now,

I’ve mine to the 6500 RPM redline a couple times. Years ago, when I owned an XJS, I used to go to 6500 RPM fairly often. With the 2.88 diff this means about 65MPH in first gear and 110MPH in second!

As the story goes the engine is safe to 7000RPM but the transmission is another story…and thus the 6500 redline. True? I dunno.

IMO, however, I really don’t feel much if any power/acceleration is to be gained after 6000RPM or perhaps even 5500RPM.

Cheers
DD

I am really curious about the sound above 6 grand. Never been there. The first time is the scariest.

Don’t do it on a wet road. When the transmission shifts you’ll find yourself going sideways

Cheers
DD

I seem to remember, my TH400 will not allow it to rev past 6000 rpm. It will upshift, even if you’re in Low. Only chance would be to get it to 6500 in D, but that would be 150mph?

I think you’re right.

I forgot that mine have shifts kits which give higher shift points and allow holding low gear longer.

Cheers
DD

I had 4 speed O/D box in my series 1 xj12 and reving beyond 6000 rpm was never hard. Sounded sweet as well.

I think it’d be more like 230 mph. No, it’ll never get there unless you drive it off a cliff.

Indeed, and I think it’s more like 5.500 rpm.
Don’t ask me how I know, but I didn’t… and it was pretty scary when it happened in a bend…

Holding the gears 1st gear in mine would max out at 65mph, second would go to approx. 115mph then 3rd would be somewhere between 140 and 160 mph, I cant be accurate with the last figure as the speedo was waving between the these 2 points… Do this a few times and then stop to re fill both tanks :wink:… The V12 sounds lovely above 4k hence why Im fitting a manual box to take advantage of the high revving nature of this unit.

The torque convertor in my 1960 SBC truck has an "anti ballooning plate " inside it. Meant to keep the convertor from distorting at super-high RPM. The stock convertor in my Jag does not, so I let the governor do its job!

Are you sure? The Jaguar-spec convertors are a bit unique

Cheers
DD

No, Doug, I’m not certain. I know that the Jag 400 converter has a higher stall speed than most, and if someone out there knows that it also has an anti-ballooning plate, please say so. Then I can drive it like I stole it!
Edit. On pages 33-34 of the Book, Roger Bywater seems to back up my thoughts, though.

I remember back in the day ( when I first got my
XJ-S sorted), and thought I would do a shake down run and try and throw in an Italian tune up ta boot.
I started out in first gear and then went to second. I was honing in on 5500 RPM and going in access of 100 MPH. If my memory serves me correctly. In the end I bailed as I was running out of road and hurtling along back to the city . I thought this was crazy at the time as our local law enforcement frowns on such experiments so I packed her in.
Maybe I’ll give it another go once I get the performance exhaust installed and see what kind of noises a V-12 can make.

Yeah, it’s very difficult with such high gearing on this car and the TH400. 1st is so noisy and can heat up the transmission if revved too high for too long. And too many times as I approach 5500 or 6000, the transmission decides to force shift into 2nd and I get a huge jerk. Do NOT want to do that in a turn or on a wet surface!

As Kirby pointed out, we’ll probably never see 6000RPM in 3rd gear.

So 2nd is the only way. But like you said, you’re doing 110-120mph, and that’s kind of hard to keep going.

One day I’d like to put a lower geared differential into my XJ-S, like 3.54:1. Hopefully I’ll be able to reach 6500RPM in 2nd at a lower speed, perhaps 90mph??? Or just go full manual transmission! :slight_smile:

I am interested in hearing how that turns out. Sooner rather than later I will have to repair my mufflers by replacing them. Old age and worn out plus noises when you shake them. From my experience my current and prior sound at high rpms was not pleasant. Mainly a harsh stressed sound probably due to the fact the exhaust is std and not turned, just set up for suppression of any and all sounds.

I found a country farm road to go up and down at will at 125mph. My only fear was an errant animal or whatever coming out of the trees. It wasn’t very long so I had to use 2nd gear to get up to 125 mph easily and quickly.

Can you tell us what that looks like? Or better yet, point to a photo?

AFAIK, the cure for ballooning is a “furnace brazed torque converter”. The idea is to make the torque converter out of some really hard steel that won’t balloon, but then you can’t weld it like a normal converter because that’d mess up the heat treatment, so instead it must be brazed together. And hand-brazing would distort it, so instead you put the whole thing in an oven and heat it to the point where the braze materials melt and flow into the joints.

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If you really wanna know, I highly recommend disconnecting the exhaust pipes right behind the downpipes, or perhaps just in front of the rear wheels. Fire that mutha up! Everyone in the neighborhood will know what you’re up to, but the sound is glorious. Sounds more like a P-51 Mustang than a Ferrari.

Sounds like a great plan when I’m doing the transition. I’m guessing a lot of people have not heard a Jaguar V-12 under those circumstances. I’m sure the boys at the muffler shop will have an appreciation.
I can hardly wait till I get the new exhaust system.
Time to wake the old girl up.

I used a TCI “Breakaway” convertor .P/n 240901. Seems a bit more expensive now than it was twenty years ago. After blowing up more than one trans. when I was, erm, younger, it made sense to go with a bullet proof unit. Without cutting open my converter to take a look I imagine the plate just looks like a metal frisbee! The truck transmission has held up well during the twenty three years I’ve owned it.