You'll need to raise the car enough to remove the rear cage as seen in the pic. Then, in a very brief nutshell, simply unbolt the old differential and install the replacement.

Plus, with the cage out, you'll want to address rear brakes and any other 'while I'm at it' items.

You're speedo reading will be way outta whack. That's another adventure.

It's all 'doable' but it'll take some work !

Cheers
DD

 

Well, I can certainly raise the car that much in my garage.

I've removed and replaced the exhaust manifolds, which was a lot of work, so I suspect I can manage this. Of course sliding the assembly out from under the car (I would imagine it's several hundred pounds) may not be so much fun.

So, I suppose I'll hunt around and see what a diff will cost.

Reading (and absorbing) all of the above posts, it seems that while a rear end change would certainly help, I wonder what else I can do.

A stomp on the gas in mine won't break it loose except on wet pavement.

Considering some of the mentioned possibilities, what (money not being an object...but of course it is)...doing which of the below would result in the best off-the-line improvement...

stall converter

change ECU

bash out the innards of the cats

final drive ratio change

Grant, can to explain a bit more about opening the exhaust and the "drive time" method?

Thanks!

John

 

Just bashing the cats up won't gain you the power a cat free engine has... Compression ratios are different. All the emissions gubbins contribute to it...

 

Make it breathe better by getting rid of the central exhaust silencers (mufflers) and fit free flow air filters.
See if you can get hold of some aftermarket air filter housings -TWR or Lister or similar.

 

Elevation makes a difference too. I have a 6.0 with a 3.54 and I can't break tires free under full throttle.

I'm at 3500' elevation, which according to the rule of thumb means ~35% loss of HP compared to sea level.

 

Even a US spec car oughta be able to get at least *some* wheelspin. Mine always did, even before any changes. It wouldn't fry the tires, mind you, but it would break 'em loose a bit.

This makes me wonder if your engine isn't performing up-to-snuff even for a US-spec model.

Have you checked for a stuck centrifugal advance? Is the vacuum advance working? Fuel filter clean?

Cheers
DD

 

Thanks as always guys.

Centrifugal advance was frozen on purchase, corrected that per Palm's book about 5 years ago. Vacuum advance was bad also, replaced it.

New fuel filter last year.

Doug, I suspect you are right, I just have an engine that needs *something* corrected on it.

It has cold air inlets (from behind the headlights), electric water pump and fans for cooling, got new plugs when new, replaced the dual coil system with a single coil, air injection and air pump have been removed, fuel sump has been cleaned out, new spark plug wires and all injection hoses replaced, all wiring that was in the V has been moved out of the V and replaced with high-temp wiring...lots more stuff but none that would have to do with engine power output (brake fluid reservoir, high wattage headlights with relays, home-made replacement for the defunct windshield wiper motor, etc). It does have +1 tires, but I don't think that's keeping it from breaking loose.

Elevation here is about 200 meters, so probably not much of a factor.

There is a dyno place in Indianapolis (just south of me), would be interesting to take it there and see how good/bad it really is.

Thanks,

John

 

From what I understand a lot of USA cars have cats in the down pipes, gutting these will help the engine breath better especially if they are clogged.

My car will spin tyres off the line and chirp and kick sideways into 2nd with a stock engine.

Removing the cage use a trolley jack and pull it out the side of the car not out the rear.

My diff uses an XJ40 3.58 LSD centre installed into the original housing, all that was modified was the pinion snout needed shortening.

 

John,

My "opening up" was simple enough. The rear HUGE resonators, behind the wheels, were rusted, city car, never got HOT enough to burn off the water. The thru cage pipes were also toast.

I replaced the front mufflers with "free flow" units, with the turn pipe custom attached, and the thru cage pipes were custom "bent" in 2" pipe as apposed to the standard 1/3/4"pipe, and then simple "Hot Dog (Google might help IF they are still made as I did this in the early 90's) resonators fitted at the rear. ALL this was done by an exhaust guy I knew that really knew his trade, and the results were/are superb.

A subtle exhaust note, NOT audible inside the cabin, but a real growl when stood on.

Drive timing:

Trimming the timing on a running V12.pdf

This might help.

Spousies PreHE Sedan S2 Fuel Infected, has the 3.31 diff and good old BW12 transmission, D Jetronic EFI Grand daddy, as standard, and that thing lights up the tyres with the greatest of ease and nowhere near full throttle, just a quick jab will launch that beast all day.

 

Not sure what you mean by "+1" but tires CAN make a difference. Some are a lot stickier than others.


Another thought is a transmission problem. A failing torque converter, specifically, can really blunt power delivery.

Cheers
DD

 

Gentlemen,

The tire store folks told me that the tires (tyres) I had them put on were one "size" wider than the tires that came with it, which of course would translate to more rubber contacting the road. They are BF Goodrich Radial T/A's, P235/60R15's, 98S M+S.

I followed Grant's timing process. Given that it's 86 F in the shade here, the sun is out, and the engine is at operating temperature, getting my face right over the distributor was not a challenge I was up to.

I was able to loosen the nut, and then I turned the adjustment screw slowly clockwise (not sure if this turns the dizzy cw or ccw, will check when things cool off). Anyway, just listening to it at idle it was happier the more I turned it clockwise.

I floored it from a stop... there was a noticeable increase in "liveliness" . It still didn't chirp the tires, but it felt like it was trying. Didn't hear any pinging.

So I continued this process until the adjustment screw wouldn't turn clockwise any longer. Stomped on the gas over and over, and no pinging. I did check to see that the locking bolt hadn't tightened, but still couldn't turn any more clockwise.

I serviced the mechanical advance per Palm's recommendation, and replaced the vacuum advance about 5 years ago.

I'm a little concerned why I would be up against a "stop" on the dizzy adjustment. I would think (but am no expert) that by continuing the turn the adjustment I would have peaked at some point, then noticed less engine happiness.

If I go with a new torque converter, I see a jump from 2400 RPM to 3000 RPM. Is the 3000 too much?

Thanks!

John

 

235/60R15 is the standard tire size on later 80ies models (my 89 had them from factory).

 

What I meant from the last sentence is that I see 2400 RPM torque converters and available, and the next "size" up that I see for sale is 3000 RPM.

Thanks,

John

 

Thanks for that Diam. I suppose somewhere along the line skinnier tires were put on this car, as I remember putting the new and old side by side, the new ones seemed like they was 1 to 2 inches wider.

John

 

Wider tyres do not necessarily mean more straight line grip it is the footprint the tyre makes on the road. Wider tyres make a wider footprint increasing latitudinal grip. If you look at topfuel dragster tyres they are tall with a long footprint.

 

havent read the whole posts!

but nothing you can do for better off line accelleration than a rear drive gear change, i have 3.73 Powerlok, Dana. my rear tires 295-35-18.

try it you will like it, still go over 130mph, with 700R4 trans.

pic enclosed!

 

JCR,

Out of curiosity have you tested or replaced the O2 sensors? I've skimmed through the post here you say your car needs something corrected, I felt the same about my car it worked but it wasn't like the videos on youtube etc, while in the shop for other reasons I had them go over the entire air-fuel-ignition spaghetti with a fine tooth comb and they found an incorrect nut was used to ground the O2 sensors which caused them to not work. This defaulted the car to a boring non-correcting fuel map.

The results post-surgery where absolutely phenomenal as was the MPG gain now 29 on hwy. Sometimes it is the tiniest thing that ruins it.

There are a couple other obscure items to look at if O2 sensors arn't a problem, such as the tiny filter baskets inside the injectors but thats abit more complicated.

 

3000 would be too much, IMO

Jaguar spec is about 2000 rpm stall. I used 2500 and was pleased.

Cheers
DD

 

Plus you have tread design and rubber compounds in the mix of variables as well.

Cheers
DD

 

Vancouver - I replaced the O2 sensors when I first got the car, about 4 years ago. I drive it a lot, but most of that driving is local, so I've not put 5,000 miles on it. I think the sensors are supposed to last much longer than that...but it seems easy enough to test them, so I will.

ronbros - did you buy the Dana in one piece (i.e., housing and all, and it just needed to be bolted on) or did you do (or have) the gears only swapped? I've been looking at justdifferentials.com and the nitro catalog, and removing and installing gears seems like quite a process.

Thanks!

John