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exhaust back box's , what's the difference

Brake buster
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Posts: 570
Joined: Sun Jul 03, 2016 8:18 pm

exhaust back box's , what's the difference

Postby Brake buster » Fri Jan 11, 2019 1:11 pm

i have a 1994 3.2s car, it has exhaust back boxes with a specific part number

does anyone know why these are different and in what way , and will earlier , and lats say it, cheaper back boxes fit , even if needing modification ?

BB
1994 3.2S in Morocco red and Doeskin/Ruby red interior
1989 V12 XJS White with Mulberry interior
2004 2.1 X-Type Platinum with Champagne Leather interior

previously ,
1999 V8 Sovereign in Seafrost with Oatmeal and Antelope interior

pimgmx
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Location: South East of the Netherlands

Re: exhaust back box's , what's the difference

Postby pimgmx » Fri Jan 11, 2019 1:39 pm

Simplest trick is to compare (JCP) the part numbers of the pipes that connect into the back boxes...
Robert will be your mother's brother if those #s turn out to be the same. ;)

the daily: 01 S8 http://bit.ly/2kIwP4m
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Erik
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Joined: Wed Dec 12, 2018 2:49 pm

Re: exhaust back box's , what's the difference

Postby Erik » Fri Jan 11, 2019 2:42 pm

pimgmx wrote:Simplest trick is to compare (JCP) the part numbers of the pipes that connect into the back boxes...
Robert will be your mother's brother if those #s turn out to be the same. ;)


Hah! Bob's your uncle ... Took me a while to make that link, good one :D
1987 3.6l Sovereign Solent Blue
1959 MGA 1500 Coupe

david
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Location: Cheshire, UK

Re: exhaust back box's , what's the difference

Postby david » Fri Jan 11, 2019 2:56 pm

Brake buster wrote:i have a 1994 3.2s car, it has exhaust back boxes with a specific part number

does anyone know why these are different and in what way , and will earlier , and lats say it, cheaper back boxes fit , even if needing modification ?

BB



There are detail differences between the late type DBC10969 and the earlier type CBC8785/CBC7517 . Most particularly the early back boxes are made of significantly better quality steel so are much more resistant to rust. The fundamental shape of the two types of pipe are the same however and the earlier pipes will fit a later car.

I have an early type back box - stamped with the part number CBC7517 (from VIN506664 to VIN594575 - and superseded by CBC8785) on the left side of my 1993 model Sovereign. The only issue I found is that the diameter of the welded bar at the rear end of the back box which fits into the exhaust mount is slightly smaller than the later type, so is marginally loose.
It is marginal on my car and hasn't caused any problems - indeed the back box seemed to 'settle down' and become as firmly fixed as the other side after my first drive in the car.

The part number for the equivalent model year's over axle pipe for each respective model year of back box may be a red herring since the over axle pipe design varies by model year and whether the catalyst is present - and not all are interchangable IIRC. The back boxes seem to all be of the same fundamental design however - apart from the very early ones.
Image 1992 Sovereign 3.2 diamond blue (1993 model)

Brake buster
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Re: exhaust back box's , what's the difference

Postby Brake buster » Fri Jan 11, 2019 5:55 pm

david wrote:
Brake buster wrote:i have a 1994 3.2s car, it has exhaust back boxes with a specific part number

does anyone know why these are different and in what way , and will earlier , and lats say it, cheaper back boxes fit , even if needing modification ?

BB



There are detail differences between the late type DBC10969 and the earlier type CBC8785/CBC7517 . Most particularly the early back boxes are made of significantly better quality steel so are much more resistant to rust. The fundamental shape of the two types of pipe are the same however and the earlier pipes will fit a later car.

I have an early type back box - stamped with the part number CBC7517 (from VIN506664 to VIN594575 - and superseded by CBC8785) on the left side of my 1993 model Sovereign. The only issue I found is that the diameter of the welded bar at the rear end of the back box which fits into the exhaust mount is slightly smaller than the later type, so is marginally loose.
It is marginal on my car and hasn't caused any problems - indeed the back box seemed to 'settle down' and become as firmly fixed as the other side after my first drive in the car.

The part number for the equivalent model year's over axle pipe for each respective model year of back box may be a red herring since the over axle pipe design varies by model year and whether the catalyst is present - and not all are interchangable IIRC. The back boxes seem to all be of the same fundamental design however - apart from the very early ones.


PERFECT 8-)

exactly the info i was asking for ,

my own car uses the 10969 and 10968 back boxes, and though are ok at the moment, they are a little rough , however, one box is NLA and no direct aftermarket replacements for some reason , but you can buy the one box for about £100 on ebay

so the other earlier part number options seem the way to go , and are much much more affordable

many thanks for the post 8-)

BB
1994 3.2S in Morocco red and Doeskin/Ruby red interior
1989 V12 XJS White with Mulberry interior
2004 2.1 X-Type Platinum with Champagne Leather interior

previously ,
1999 V8 Sovereign in Seafrost with Oatmeal and Antelope interior


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