Original Compression Ratio - 4.0 RV8

garrycol · Post by **garrycol** » Wed Sep 21, 2016 9:03 am

Is there a way of determining the original compression ratio of a 4.0 RV8 from the engine number. The block had been previously skimmed and the "dot matrix" engine number and compression ratio removed and just the engine number stamped back on.

The engine number is 55D03758A and was in a Disco 2.

Thanks

Garry

russell_ram · Post by **russell_ram** » Thu Sep 22, 2016 8:20 am

Compression ratio on a factory engine is determined by the pistons - what part number are they? How deep is the piston bowl? You can 'visually' tell the difference between HC and LC pistons.

If it's a UK engine though it is highly likely to be 9.35:1

garrycol · Post by **garrycol** » Thu Sep 22, 2016 11:00 am

Thanks - but the pistons now live inside the engine so not sure of the part numbers (I would need to know the Vin of the original vehicle that I do not have)

I live in Australia so is an Aussie engine.

There are plenty of listings online for comp ratio vs engine number but not for 4.0s fitted to the Disco 2. I was hoping someone might know of a list that I may have missed.

Cheers

Garry

garrycol · Post by **garrycol** » Thu Sep 22, 2016 11:57 am

PS I have continued to look into this and came across a forum where there is a post on the very issue I have raised - Disco 2 4.0 engines starting with 55D are low comp.

So question solved but none of the RV8 engine number lists have listings for Disco 2 4.0s - RR 4.0s yes but not the Disco 2.

Cheers

Garry

russell_ram · Post by **russell_ram** » Fri Sep 23, 2016 7:00 am

From a file of list of engine numbers hidden in the background of my laptop (dated April 2002).

55D 4.0 Litre Tempest Low Compression
56D 4.0 Litre Tempest High Compression

Tempest is LR internal name for Disco 2. Low comp in these terms is 8.13:1

HTH

garrycol · Post by **garrycol** » Fri Sep 23, 2016 9:50 am

Thanks for the confirmation - just what I needed.

It is a shame that information on the D2 engines does not appear on all the engine number sites.

Cheers

Garry

garrycol · Post by **garrycol** » Fri Sep 23, 2016 9:55 am

Thanks for the confirmation - just what I needed.

It is a shame that information on the D2 engines does not appear on all the engine number sites.

Cheers

Garry

russell_ram · Post by **russell_ram** » Fri Sep 23, 2016 10:59 am

No problem. If you had better fuel in Oz you could've had the high comp engine LOL. I spent some time in Parramatta back in the late 90's working on some service issues at LR Australia HQ on D2 and 38A Range Rovers.