[Lumps!] Question about the rear end

Lumps
1

Ok, so I have a 72 XJ6 conversion… My engine has a bad valve,
and the tranny has been freaking out in OD… So I’m having some
money coming my way that I intend to use on the car. There is the
option of fixing what’s there… OR crate engine maybe. I can’t
(unfortunately) do the work myself so it’s going to be a grand or
so just to fix the lame head on the gutless 70s engine, or spend a
few grand on a crate. A new built 700R4 is another couple grand.
Install, not sure on the pricing but I’m sure I could handle it
with the amount of money I’m going to have.

So my question is, how much power can the stock rear end take, and
is there anything else on the car that might need to be dealt with
for whatever level of power the rear end can take.

I’d like to think this through and see if the crate engine/tranny
is feasable right now, as that’s how I’d like to go eventually. I
think if I have to redo the rear end and reinforce the chasis for a
signifigant power boost that throw that idea out the window for
right now at least. But if the engine and tranny is all I have to
worry about, I think I can swing it ok. It just seems that if I;m
going to shell out a couple grand potentially to deal with what’s
there and still end up with meh stuff that it might be better to
suck it up and put the better stuff in there now.

Thanks in advance!–
Black On Black 1972 Jaguar XJ6 Powered by A Chevy 350
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2

The Jag differential is very rugged. You diff may eventually wear out but in
several years of reading Lumps postings I don’t ever recall hearing of a
diff failure because of too much engine

Doug Dwyer
Longview Washington USA
1995 XJR
1988 XJS V12 Coupe

So my question is, how much power can the stock rear end take, and
is there anything else on the car that might need to be dealt with
for whatever level of power the rear end can take.

//please trim quoted text to context onlyFrom: “exer51” vaughn_kiefer@hotmail.com

3

In reply to a message from exer51 sent Wed 29 Nov 2006:

The differential is a version of the well known and respected DANA
44. It will take all the power you are likely to give it without a
whimper.

There is a racing Jaguar see Draguar.com!

A lot depends on which CHEVROLET you have> Most will give you
plenty of power.

A good 3 angle valve job will restore plenty of pep to the one you
have, whatever, it is. Do you have a 307 Smog motor? If so, that is
a relatively ‘‘weak’’ engine. No. I see you have a 350. A valve job
and a tune up and it will give you plenty of power.

Look on EBAY or Craig’s list and find a used good motor if it is a
a worn out 350. Same with the trans, good used ones can be found.
The problem is that yout mechanic will be ‘‘touchy’’ about installing
them as he will fear being blamed for any shortcomings.

Therefore, a rebuilt trans and a valve job will get you a pretty
good running car, at the least risk & probably $'s.

Black on black with a 350 = GREAT!!!

My 83 XJ6 has a 94 Cadillac LT1. I installed it. A lot of $'s, but
it sure does run good!

Carl aka JAGCAD–
The original message included these comments:

Ok, so I have a 72 XJ6 conversion… My engine has a bad valve,
and the tranny has been freaking out in OD… So I’m having some
money coming my way that I intend to use on the car. There is the
option of fixing what’s there… OR crate engine maybe. I can’t

–
Carl Hutchins
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4

In reply to a message from exer51 sent Wed 29 Nov 2006:

Hi 51,
For the most kick for your cash without terrorising the
driveline I suggest that you lock up that Convertor.
I would suggest a crate motor with carby.I have a GM 350/355/405
with a TH700 auto and there is NO need for more for your car to
be a Joy to drive.Why not try a 1’’ sway bay from Andrew which
will be an asset,Good handling is worth Extra Ponies.What ever
you decide all the best from Kelpie in Australia.
P.S. The ZZ4 395 has larger Inlet valves with same Cam .–
The original message included these comments:

Ok, so I have a 72 XJ6 conversion… My engine has a bad valve,
few grand on a crate. A new built 700R4 is another couple grand.
I’d like to think this through and see if the crate engine/tranny
right now at least. But if the engine and tranny is all I have to
Black On Black 1972 Jaguar XJ6 Powered by A Chevy 350

–
nwf
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5

In reply to a message from Doug Dwyer sent Wed 29 Nov 2006:

Hi D/D,
The most I have seen in power and long term durability was a
1974 with a 454/468 B/Block that claimed 450 HP and 500/Tq,.
The owner had the car for over 10 years so it must have been
good to own…Kelpie in OZ…–
The original message included these comments:

The Jag differential is very rugged. You diff may eventually wear out but in
several years of reading Lumps postings I don’t ever recall hearing of a
diff failure because of too much engine
Doug Dwyer

–
nwf
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6

In reply to a message from kelpie sent Wed 29 Nov 2006:

Hello and thanks for the responses. In response to the one who
suggested giving my own 350 a working over for some extra juice.
Thing is I eventually want some REAL power. I’m not just shooting
for 200 something HP under the hood. Ultimately I’d probably like
to get into the 400s, potentially even higher. I don’t want to turn
it into an outright drag car or anything, but I’d like to have a
very, very peppy cruising car.

My thought is simply that it’s better to start with either a brand
new engine, or a crate engine that was inspected and OKed for high
power professionally. You never know if some hairline crack int he
block on my engine will crop up without going through the same
troubles with mine, and IMO it’s easier to just get a crate that
has all it’s parts matched to work well with each other and a good
block.

That 454 BB is basically what I was wanting to know. Only question
is was his rear end stock too… 400/500HP isn’t all that much
power for many older cars as they were built to be beefy, however
some wouldn’t be able to endure for the long haul. If you know his
rear end was stock please let me know, because that would be great
news.–
Black On Black 1972 Jaguar XJ6 Powered by A Chevy 350
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7

In reply to a message from exer51 sent Wed 29 Nov 2006:

Check with John’s Cars in Fort Worth, Texas!

He has a big block Chevrolet kit!

Big block Cadillac too!

Read GM performance on their work ups on the LT1 or LS1!

A good used Block is felt to be superior to an unseasoned new one
when it comes to modifications by some machinists. NASCAR does not
throw their blocks away aftert each race. They are refreshed a few
times and thaen discarded. If you can find access to a used NASCAR
motor you will get HP.

What are your SMOG plans, if any required., and your 72 year may be
the key to that!!
The power comes on top! The longevity comes from the bottom!

A top set of after market heads & good induction system will get
you into the HP #'s you are looking for.–
The original message included these comments:

My thought is simply that it’s better to start with either a brand
new engine, or a crate engine that was inspected and OKed for high
power professionally. You never know if some hairline crack int he
block on my engine will crop up without going through the same
troubles with mine, and IMO it’s easier to just get a crate that

–
Carl Hutchins
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8

If the machine shop is worth anything they should magnaflux a block anyway

Before a rebuild I always have the machine shop go through it, sure is nice
to know if you got a piece of Do Do before you pour money in it.
I like to flush when it’s time to flush, not wait till I’m done…
If you know what I mean-----Original Message-----
From: owner-lumps@jag-lovers.org [mailto:owner-lumps@jag-lovers.org] On
Behalf Of cadjag
Sent: Wednesday, November 29, 2006 3:56 PM
To: lumps@jag-lovers.org
Subject: Re: [Lumps!] Question about the rear end…

In reply to a message from exer51 sent Wed 29 Nov 2006:

Check with John’s Cars in Fort Worth, Texas!

He has a big block Chevrolet kit!

Big block Cadillac too!

Read GM performance on their work ups on the LT1 or LS1!

A good used Block is felt to be superior to an unseasoned new one
when it comes to modifications by some machinists. NASCAR does not
throw their blocks away aftert each race. They are refreshed a few
times and thaen discarded. If you can find access to a used NASCAR
motor you will get HP.

What are your SMOG plans, if any required., and your 72 year may be
the key to that!!
The power comes on top! The longevity comes from the bottom!

A top set of after market heads & good induction system will get
you into the HP #'s you are looking for.

//please trim quoted text to context only

9

In reply to a message from exer51 sent Wed 29 Nov 2006:

Hi Vaughn…
I have a 383 in my Series One. It’s a roller cam RV crate motor
with 4bbl. carb,700R-4,XJ-s rear end which gives it posi traction.
Somewhere between 350 and 375 hp I suppose.
Cost about 6500 for the stuff and nothing for the work.
Car had a ford 302 in it when I got it,so I didn’t ‘‘ruin’’ it.
(Unless yer a ‘‘fordnut’’!?!)

My advice is to do what Carl said and get yours a valve job and
fix whatever…then you’ll know what you’ve already got.

I don’t think your problem will be the rear end…you will need
a ‘‘built’’ transmission.

I think Andrew did a lot of work to the body attach. in the
back…search the archives…and I’ll bet you could buy one already
done from someone for less than you’ll spend.

I think it’s a hot rod thing, and most of the fun is the scheming
and watching it grow…more art than science!
Your age and peer group and the magazines you read have more to do
with it.All it takes is money…but you might as well have fun with
what you got while you get it together.

For me, I’ve also got a '86 V12, and that’s the perfect car for me
for cruising,
It was given to me with a bad engine…run without oil… and I
sold a bunch of old car stuff I had and paid about 6500 to get it
overhauled and running right.No other money went into it but if I’m
ever rich there’s still plenty to do to it to pep it up.
Same price, better cruiser, lot’s of power, more ‘‘equity’’ and
future classic value.
So I’ve got one of each and love 'em both but I’m almost 75 and a
little more of a realist than when we built the 383.
If I have to sell one I’ll sell the 383.
Carl is an older guy too, and he’s happy with his car…that’s what
I’d have built…a caddy 500 drops in…So build what you want!!
But do the valves,fix the other things and drive what you got while
you ask questions.You already will have way over 200 hp if that’s a
350 sbc.
And save up because it wont be cheap !!
I’m not telling you what you tell your wife…but it is the truth!
I got good advice from this list and the guys are still on here so
keep asking…I’ve told you what I know and that’s not much.
John’s cars in texas is where I got my kit and he has stuff for
putting in a Big Block,as well as the sbc.Also comments on it.
I think you said you’ll have some money soon…just don’t overlook
what’s real just out of eagerness, and run out before you get it
done.
And look for rust before you do it !!
Enough old guy talk already !!
Bill–
The original message included these comments:

Thing is I eventually want some REAL power. I’m not just shooting
for 200 something HP under the hood. Ultimately I’d probably like
to get into the 400s, potentially even higher. I don’t want to turn
it into an outright drag car or anything, but I’d like to have a
very, very peppy cruising car.

–
Bill de Creeft AlaskaSeaplanes.com
Homer, Alaska, United States
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10

In reply to a message from Wm de Creeft sent Wed 29 Nov 2006:

Try an ebay search. I just did one. I found complete LS1, LS2, LS6
takeouts with trans ( auto or 6 speed) front $3000.00 to $4900.00.
Complete w/ wiring, computer, accessories etc. The highest priced
one had 14000 miles on it. These motors are more powerful than
there gen 1 and 2 smallblocks AND do it with better fuel economy. I
have a lumped 89 xjs conv. with a TPI L98 and 700R4 trans. Very
happy with its performance, even with the anemic 2:88 gear. BUT if
I were to do it again, I would, WITHOUT A DOUBT, do a gen 3
smallblock. A little extra money? Maybe. Better performance and
fuel economy and a lighter combination tell me that is the way to
go for anyone considering a fresh lumping project. Andrew @ Jaguar
Specialties is working on these conversions as we spea…type!
My $0.02–
Rob Wade
Windsor Ontario, Canada
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11

Dear fellow Lumpers,
I have an S2 75 XJ6L conversion here in CA, basically
homemade - no kit. The engine has a performance chip,
airfoil in throttle body, K&N, 165deg thermostat and I
was wanting to add freeflow headers as I am in the
position of factoring a new exhaust system myself.
Question is as the 75 year does not require a biannual
smog test - is there any advantage to removing the
catalytic converter, air rails and the like, I know I
will still need the EGR etc. or will I ?

Any suggestions ? Will doing these things constantly
throw engine codes ? or simply make me a polluter. I
know the obvious answer is to put in an LT1 but I’m
just at the motor learning stage. Anyhelp would be
appreciated.

Cheers
Nick
75 XJ6L with an 86 Chevy 305TPI/700R4 with Golde
sunroof, big eyes and euro bumpers.

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12

In reply to a message from exer51 sent Wed 29 Nov 2006:

HI 51,
I did not realise that you wanted POWER!!
From what I see in the G.M. crate motors U have 4 Good options.

 [1] ZZ383//425 HP//449 Tq =Proven and reliable track record..
 [2] ZZ454//440 HP//500 Tq 
 [3] LS6 //405HP//400 Tq [Sump pan may be unsuitable. Check with
 other Lumpers who have done this conversion recently.]
 [4] 502 with either 450 or 500 HP [550//567 Tq]=Too much??? 
 
 Don't forget the cooling problems that are inherent with the 
 lust for Power.--

The original message included these comments:

In reply to a message from kelpie sent Wed 29 Nov 2006:
Hello and thanks for the responses. In response to the one who
to get into the 400s, potentially even higher. I don’t want to turn
very, very peppy cruising car.

–
nwf
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13

In reply to a message from NICHOLAS GILLITT sent Thu 30 Nov 2006:

I have nothing but the cats left on mine. I removed the air pump
and added the factory delete pully, added headers, and pulled all
the tubing. I run dual 2 1/2’’ cats and the car runs like a scared
rabbit! I do not have any check engine lights coming on and the car
flew through last years e test with no issues at all. I DID back
the timing down from the factory 6* (1989 camaro L98 motor and 700R
trans) to zero to increase the cylinder temps. The levels on the
test were half of the allowable limit. The car will be REALLY lazy
but blow clean as can be, if everything else is fuctioning as
intended. You may have a visual inspection issue in CA. I would
leave the cat IF its a hi flo model. No need to pollute if you
don’t have to. I wouldn’t jump to conclusions on the LT1. My L98
will more than hold its own against a surprising amount of mustangs
etc. I weigh more than them, kick they’re ass, and look better
doing it! The pics of my motor are in the lumps photos. ‘‘The new
motor is in’’.–
Rob Wade
Windsor Ontario, Canada
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14

In reply to a message from NICHOLAS GILLITT sent Thu 30 Nov 2006:

How about a SMOG test on transfer?
Put the stuff back on or just drive it until it’s gone!

How did you get all this smog tested to begin with?

The converter if it is a good one hurts nothing. But if you go to
true duals, it would mean adding one, which you probably don’t want
to do! The NOX will go up.

EGR is beneficial to running more advance on present day fuels.

No cats and no EGR will make you a polluter!

The ar pump and rails do little, except clutter the engine bay and
keep smog gods happy!

I know of a GM directive advising on removal of the air pump &
system on 95 LT 1 cars

I am not sure just what your ECM would tolerate without throwing
codes!

But a clean well tuned engine goes a long way towards not being a
polluter.

Get an LT1, or later, they are great.

Carl aka JAGCAD

83 XJ6 94 Cadillac LT1

94 Jeep Grand Cherokee Laredo–
The original message included these comments:

Question is as the 75 year does not require a biannual
smog test - is there any advantage to removing the
catalytic converter, air rails and the like, I know I
will still need the EGR etc. or will I ?
throw engine codes ? or simply make me a polluter. I
know the obvious answer is to put in an LT1 but I’m
just at the motor learning stage. Anyhelp would be
appreciated.

–
Carl Hutchins
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15

In reply to a message from kelpie sent Thu 30 Nov 2006:

The ZZ383 would probably be the best choice. Cheap, carbed, normal
old style SBC.

An LS1/2/6 however would be awesome. I was looking around on ebay,
and you can find LS v8s with 4L60 trannys for a reasonable price.
Only question is how easy is the engine going to be to bolt in…
The mounts were changed for the LS engines over the old SBC. I have
kept up with this guys project

Apparently he just used some mount adapters that bolt to the block
that make it fit the old SBC design. I just dunno if that would be
a good thing though, I mean 2 adapters for the engine mounts…
Sounds like a recipe for the engine just falling out of the car one
day when you’re revving it good.

But the LS engines would of course be the ultimate. You can get
oodles of power out of them easily, they’re lighter, better
mileage, ect. They even make a standalone computer for them
specifically for using in old hotrods that were carbed originally!
I’d probably be better off finding one that was just the engine, as
I’m not sure if those standalone computers deal with the tranny as
well, so an older non electronic 700R/4L60 might be better than a
4L60e.

Decisions, decisions. I did get my questions answered though about
the rear end. Apparently it can take as much power as I’m wanting.
So now it’s just a matter of running the numbers to see if I can
spring for what I want now and get it done right, or if I’ll just
have to deal with the engine that’s in it for longer while I put
away more money for the project.

There is a place up the road from where I live that not only
specializes in Jaguars, but specifically in doing lumps. I think
I’ll have to give them a call and see if I can get some ballpark
figures for what an install would be, especially for an LS V8 :slight_smile:
God willing I’ll hear something I like.

Thank you guys for your help. This board is awesome, you’re always
great about answering questions.–
The original message included these comments:

 [1] ZZ383//425 HP//449 Tq =Proven and reliable track record..
 [3] LS6 //405HP//400 Tq [Sump pan may be unsuitable. Check with

–
Black On Black 1972 Jaguar XJ6 Powered by A Chevy 350
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16

If I can jump in here for a minute I would highly recommend looking into a
lt1 4l60e COMBO. They are cheap good to over 15000 miles and great mileage
to boot.

GARY

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17

In reply to a message from exer51 sent Thu 30 Nov 2006:

Hi 51,
IF U wanted to build up your own Special 383 from your 350 block
try reading John Lingenfelter’s Great book on modifying S B Cs
I used quite a few of his ideas when I had my 350 rebuilt and I
found that every thing written that I tried was HONEST,Accurate
and reliable. All the best… Kelpie in Australia,–
The original message included these comments:

The ZZ383 would probably be the best choice. Cheap, carbed, normal
old style SBC.
Sounds like a recipe for the engine just falling out of the car one
day when you’re revving it good.
well, so an older non electronic 700R/4L60 might be better than a
Black On Black 1972 Jaguar XJ6 Powered by A Chevy 350

–
nwf
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18

In reply to a message from Craig Smith sent Wed 29 Nov 2006:

Hi Craig,
When I had my My 010 350 block set for rebuild I had it Sonic
tested after cleansing.I wanted to have the block and heads stress
relieved with old method of heating the totally stripped items at
500+ degrees for 12 hours and a similar time for cooling down.This
was not possible under the circumstances.
Altogether the block was flushed,tubbed and scrubbed 3 times
and
assembly was done in a dust free room.You are dead right about
getting the job done properly…Start well-finish well…
All the very best…Kelpie in Australia…–
The original message included these comments:

If the machine shop is worth anything they should magnaflux a block anyway
I like to flush when it’s time to flush, not wait till I’m done…
If you know what I mean

–
nwf
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19

First, thanks for all the great advice.

Just as a little background - the car will never be
sold so a SMOG on exchange will never be an issue.

Originally when I dd the conversion about 8 yrs ago it
was with a 92 caprice TBI 305. This was DMV inspected
and passed and I have the bar code sticker on the door
panel. That motor was SMOG tested 2 yrs later and
passed but has since died. I then transplanted a
rather tired TPI 305 from an 86 IROC Z28 which failed
its SMOG on emmisions but no mention of diference in
engine - the two engines have very much the same
emissions requirements.

I did the heads to get it to pass (valve seals were
the problem) but exactly at that time the law changed
and 75 or older cars now no longer require a SMOG test
in CA.

The law changed 2 yrs ago and from initially requiring
a SMOG test for my registration to be complete I was
granted a registration automatically upon the law
change. Just in november is the first renewal since
then and again no SMOG required - full registration
granted.

In my mind this means I can put what I want in there
as it will never be seen by the SMOG inspectors again

  • UNLESS they change the law.

Is this correct for California OR am I living in a yet
to be discovered loophole - would be nice to know
before I go tinkering and removing cats etc.

Nick 75 XJ6L 305TPI/700R4
Golde sunroof, big eyes and euro bumpers

You may have a visual inspection issue in

CA. I would
leave the cat IF its a hi flo model. No need to
pollute if you
don’t have to.

//please trim quoted text to context only— Rob Wade robsxjs@hotmail.com wrote:

20

In reply to a message from NICHOLAS GILLITT sent Thu 30 Nov 2006:

I think your caution is wise. I think that the exemption by year
from bi-annual SMOG inspection does not create an open book on
removal of heretofore required emisions equipment.

As to how it is enforced, who knows. I would suggest getting the
law and reading it. Your State legislature representative should be
able to get the Bill that became law. I don’t think I would go into
my motives too clearly with her except that you do have an old car
and would like to know exactly where you stand.

I would counsel, keep the cats & put the air pump & stuff away for
another day.

Good luck with your car.

Carl–
The original message included these comments:

The law changed 2 yrs ago and from initially requiring
a SMOG test for my registration to be complete I was
granted a registration automatically upon the law
change. Just in november is the first renewal since
then and again no SMOG required - full registration
granted.
Is this correct for California OR am I living in a yet
to be discovered loophole - would be nice to know
before I go tinkering and removing cats etc.

–
Carl Hutchins
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