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oneten110



Member Since: 02 Jul 2011
Location: Auvergne
Posts: 235

France 
Compression ratio

Can anybody confirm that the CR for a 4.2 V8 is 7.94:1 please?
I think I remember reading that it was a low compression engine so it could run on the low octane petrol in USA

Post #717244 11th Jul 2018 10:28pm
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discomog



Member Since: 09 May 2015
Location: Notts/Lincs Border
Posts: 1191

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Santorini Black

I have a spec sheet for the 4.2 but unfortunately does not give the CR. As you are probably aware the 4.2 is relatively rare compared with 3.9 or 4.6 and was only produced from 1994 to 1996. It unfortunately suffered from cylinder liner problems. Santorini 90XS SW
Discovery Sport
Morgan Plus 8

Post #717270 12th Jul 2018 8:48am
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
Posts: 6139

United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey

A quick Google suggests that it's 8.94:1. This is the best reference that I found:

http://forums.roversnorth.com/showthread.p...-2-engines 

MY USW BUILD THREAD

Post #717271 12th Jul 2018 9:06am
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oneten110



Member Since: 02 Jul 2011
Location: Auvergne
Posts: 235

France 

Thank you gentlemen.
I have an early 4.2 in my One_Ten, from a scrapped RR Vogue LSE.

No liner problems thus far, it uses hardly any oil or water and it works quite hard for its living. It is more economical than the previous 3.5 Rolling with laughter by about 2mpg

Post #717351 12th Jul 2018 6:04pm
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diesel_jim



Member Since: 13 Oct 2008
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United Kingdom 2006 Defender 110 Td5 SW Epsom Green

LandRoverAnorak wrote:
A quick Google suggests that it's 8.94:1.


Agree.... looking at the Russian EPC site at the 4.2 classic RR pistons (STC1191) then ending up at Turners website they state "STC 1191 Piston assembly including rings, gudgeon pin. 8.94:1CR "



https://www.turnerengineering.co.uk/stc-11...2x20634396

Post #717365 12th Jul 2018 7:29pm
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oneten110



Member Since: 02 Jul 2011
Location: Auvergne
Posts: 235

France 

Better take care of it then because crankshafts and real pistons are no longer available. Though apparently brit part do the pistons.
Lest anybody is wondering why the original question, I have just fitted a pair of late heads to the engine and used composite gaskets, I was wondering what difference it would make to the CR if I used original type tin gaskets

Post #717374 12th Jul 2018 7:58pm
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Devon-Rover



Member Since: 22 Jan 2015
Location: South Devon
Posts: 601

United Kingdom 2014 Defender 110 Puma 2.2 USW Aintree Green

The difference would be marginal in terms of CR and it's effects Also can be found on Fb, Ytube, Insta & Twitter @4WDSouthwest

Post #717431 12th Jul 2018 10:46pm
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oneten110



Member Since: 02 Jul 2011
Location: Auvergne
Posts: 235

France 

I am guessing that Land Rover reduced the size of the combustion chambers on the later heads (by 8cc) to compensate for the additional thickness of the composite gaskets?
If that is the case and with no additional factors, by my fairly basic reckoning changing from composite to tin gaskets would bump the CR from 8.94 to 11.03

Post #717602 14th Jul 2018 6:35am
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discomog



Member Since: 09 May 2015
Location: Notts/Lincs Border
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United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Santorini Black

oneten110, yes you're correct they reduced the volume from 36cc down to 28cc to compensate for using a composite gasket. I know on the 4.6 if you use a metal gasket it will increase the CR by 14% and on a 4.0 it will increase by 16% Santorini 90XS SW
Discovery Sport
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Post #717613 14th Jul 2018 7:45am
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