3B/7A Block difference

[Ian Simmonds]

Assuming the con-rods etc are being replaced and low compression pistons fitted, are there any fundemental differences between a 7A and a 3B bottom end... I'm thinking oil spray jets etc.

Many thanks

Ian

[Mark Halligan]

Apart from the larger bore size on the 7A, the oil return for the turbo (below the oil filter)if you are using the 7A block, is missing but the boss for it is there, so it could be added with no probs.

The 7A has oil squirters, I don't think I've missed anything else...if I have I am sure someone else will know.

I am using a 7A crank in my engine and it was the same as the ABY crank.
Cheers

[Mark Halligan]

More crank info here

http://www.s2forum.com/forum/showthread.php?t=8550

[Mark Halligan]

7A block info here

http://www.s2forum.com/forum/showthread.php?t=16598

[Puglife]

Block has oil squirters already ian, and as mark says the oil return point is there just the hole is not milled out.

[4WheelDrifter]

You can use the A/C sump for the oil return, if you don't fancy drilling the block.
You'll also need to change the centre core plug for the turbo water return.

[UrS4boy]

You can use the A/C sump for the oil return, if you don't fancy drilling the block.
You'll also need to change the centre core plug for the turbo water return.

I didn't realize that the turbo water return went to a modified core plug until I was looking at my spare AAN on the engine stand. Not too fancy but I guess it works (looks like a homemade bodge to be honest).

Dave F.

[Jamo]

The big thing to consider here which Mark has already pointed out is the bore size

The 7A IIRC is 82.5mm and the S2 is 81mm which means the standard RS2 metal head gasket can't be used so you will have to carefully consider you options for pistons and head gasket.

[terrybullwon]

The big thing to consider here which Mark has already pointed out is the bore size

The 7A IIRC is 82.5mm and the S2 is 81mm which means the standard RS2 metal head gasket can't be used so you will have to carefully consider you options for pistons and head gasket.

Yes you are correct Jamo,

I have some RS2 Gaskets machined out to 83mm, using the torque plate in my thread. A few forum members now are using the 7A block.

[Flat on my back]

Wot...

Stop it now...i wont have you all copying my idea...leave them 7A blocks alone i need them all...