[xj40] 3.6 Pistons

Hi, does anyone know whether the 3.6 litre XJ40 engine uses cast or
forged pistons? I also need an idea of how much extra power the
standard transmission will take, years ago I seem to remember
seeing some turbo charged examples floating about, did they use the
original transmissions and back axles?

Cheers Guys, Bruce.–
Bruce - 1989 XJ40 - tired but still running
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In reply to a message from brucek sent Sun 16 Apr 2006:

Bruce,

I believe the pistons for the 3.2, 3.6 and 4.0 litre are the
same (for the same compression ratio) and they are all cast
to BS1490-1970 LM13TF.
Don’t know about the tranny on the twin turbo ‘Chasseur’
version of the XJ40. Do a search on that name to see if you
can dig up that info.–
The original message included these comments:

Hi, does anyone know whether the 3.6 litre XJ40 engine uses cast or
forged pistons? I also need an idea of how much extra power the
standard transmission will take, years ago I seem to remember
seeing some turbo charged examples floating about, did they use the
original transmissions and back axles?


Bryan N, '91 Sovereign 4.0 L, (RHD)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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In reply to a message from brucek sent Sun 16 Apr 2006:

Bruce,

I believe the pistons for the 3.2, 3.6 and 4.0 litre are the
same (for the same compression ratio) and they are all cast
to BS1490-1970 LM13TF.
Don’t know about the tranny on the twin turbo ‘Chasseur’
version of the XJ40. Do a search on that name to see if you
can dig up that info.

so, could I swap the crank from a dead 4.0 in a 3.6 and get away with
it, or is there more to it?–
Arnoud

iMac, therefore I am

http://www.se7en.nl

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In reply to a message from Arnoud sent Mon 17 Apr 2006:

Arnoud,

No. - the difference between the engines is the stroke, so
the crank throws and con-rods are different ;-

3.2 litre = 83mm stroke
3.6 litre = 92mm stroke
4.0 litre = 102mm stroke

The bore is the same for all three capacities - 91mm, but I
assume there has to be some difference in the height of the
cylinder block unless the difference in TDC is catered for
by the different con-rods specified for each capacity -
otherwise fitting a 4.0 litre crank, con rods and pistons to
a 3.6 block would blow the head off!–
The original message included these comments:

so, could I swap the crank from a dead 4.0 in a 3.6 and get away with
it, or is there more to it?


Bryan N, '91 Sovereign 4.0 L, (RHD)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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Hi,

Transmission will take almost anything, I am not sure about the back axle�on
a 3.6. In case you are planning an increase in performance, an axle from the
XJ12 is a direct fit.

From: “brucek” bruceakop@aol.com
To: xj40@jag-lovers.org
Subject: [xj40] 3.6 Pistons
Date: Sun, 16 Apr 2006 23:18:23 +0200

Hi, does anyone know whether the 3.6 litre XJ40 engine uses cast or
forged pistons? I also need an idea of how much extra power the
standard transmission will take, years ago I seem to remember
seeing some turbo charged examples floating about, did they use the
original transmissions and back axles?

Cheers Guys, Bruce.

Bruce - 1989 XJ40 - tired but still running
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from LLuis Gimeno sent Tue 18 Apr 2006:

The cylinder blocks are interchangeable from 2.9 through to 4.0.

The 3.6 and 4.0 use conrods nominally 166 mm between centres.
The 2.9 and 3.2 have 175 mm rods.

Pistons are cast and different for each application - how else
would the correct deck height and compression ratio be obtained?–
The original message included these comments:

Hi, does anyone know whether the 3.6 litre XJ40 engine uses cast or
forged pistons? I also need an idea of how much extra power the
standard transmission will take, years ago I seem to remember


Roger Bywater / AJ6 Engineering
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Old thread, but for future reference as it pops up on google for ‘XJ40 conrod’:

As Roger mentions, the 4.0 and 3.6 conrods are the same. Workshop manual states 166.32-166.42mm between centres 3.2 and 2.9 conrods are also the same at 175.185-175.285mm between centres.

AJ16 conrods have the same dimensions, but are different in production. For one they lack the balancing pad underneath. They’re a little lighter than their AJ6 equivalents, and are direct replacements for the AJ6 parts.

The Mahle catalogue quotes the compression height of the 3.6 piston as 41.9, and the AE Hepolite catalogue quotes 41.97. I’m not sure which is correct, but I’ve done my calculations based on the Hepolite figure. If that’s right then the deck height of the AJ6/AJ16 is 254.34mm (provided the pistons are flush with the top of the deck). Pretty confident all deck heights are the same.

That gives the compression height of the various iterations as:

2.9 - 41.605mm
3.2 - 37.605mm
3.6 - 41.97mm
4.0 - 36.97mm

I’ve done a quick search to see if there’s a possibility of using the longer 175mm rod in the 4.0 engine, needing a compression height of 28.105mm. Unfortunately that’s pretty short for a 23.815mm gudgeon pin! Not a great deal of space above it for rings, and no direct fit OEM pistons for a 91-91.5mm bore (at least in the Mahle catalogue, haven’t checked the Nural/Hepolite one). Closest I’ve come is Mahle 001 06 01 pistons from a W202 Mercedes C230K which are 91.4mm, 30mm compression height, and a 22mm pin. Close, but no cigar. Would probably need to be custom.