Thread: GEMS 3.9 conrod length Please

Originally Posted by Pedro_The_Swift

Centre to centre,, should be in that RAVE...

Hmm not sure what engine you are wanting information on - the 3.9 or 4.0.

As far as I am aware the 3.9 was a 14CUX Hotwire and the 4.0 was intially GEMS and later Thor. So as far as I know, unless modified, the 3.9 was not a Gems engine.

Now the 3.9 and 4.0 engines have exactly the same capacity (4.0 has larger diameter crank journals) but the bore and stroke of both engines are the same at 94mm.

From my V8 engine rebuild book, the 3.9 connecting rods are 143.71 to 143.81 mm between centres.
The 4.0 connecting rods are 155.12 to 155.22 mm between centres.

So you need to work out which engine you have - as Gems was not fitted to the 3.9 as standard.

Garry

Thanks Garry.

All the 4L are thors, all the 3.9's are whatever you want to call that engine.
All the thors are actually crossbolted,
and, as you have proven, all the Thors have longer rods and shorter pistons.

something to do with piston slap and rod angles....

Originally Posted by Pedro_The_Swift

Centre to centre,, should be in that RAVE...

From RAVE for the P38A:

Connecting rods
Length between centres:
4.0 litre 155.12 to 155.22 mm .................................. 6.10 to 6.11 in
4.6 litre 149.68 to 149.78 mm .................................. 5.89 to 5.91 in