Engine designations and parts interchangeablitly?

[Ian Simmonds]

Re. the cranks,they are different on some 7a vs 3b that ive seen,the shape is same but they are sometimes cross drilled in different places,not sure why.There is a picture on here somewhere,someone has 2 side by side with tie wraps poked through the holes to show the difference.


ps ive dug out another 7a bottom end that i want rid of,sooner the better or it will get binned.Free to collector.

If they are crossdrilled through the 'loab's' of the crank this may just be a method of balancing. It's something I've seen on large marine and locomotive cranks.

[S2central.net]

Can someone post up a useful pic of the timing belt tension arrangement on the 3B for comparison - the family album sure lists differnt parts required.

I just received some ABY timing belt parts this week and was comparing notes with Andy_Casey. I went for the S2 belt and water pump - that has 29 teeth. He went for the faster flowing RS2 pump (26 teeth) and its shorter belt.

I had ordered the tensioner/damper listed for ABY which also includes the relay roller. I was expect some kind of spring loaded hydraulic tensioner for the belt but its just a static metal bracket that must be rotated to apply tension to the belt. All you need to buy is the relay roller - save yourself some wedge.

Pretty sure on the 3B, the block is slightly different as the belt is tensioned by the coolant pump and that there is no relay roller.

Looking at it on the parts system, I'd say a KV block could accomodate the 3B timing belt setup with little or no drama.

Paul

[S2central.net]

I have a 3B block waiting for me, but you know if I find an old KV engine with a fooked head in a scrapper one day, I might just have to nobble it for the bottom end

[4WheelDrifter]

There's nothing different on the 3B block apart from having no holes like the ABY has for the tensioner.
On the 3B the relay roller is on the oil pump housing and the water pump mounting holes are slotted to tension the cambelt. That's why these parts differ from the ABY.

[S2central.net]

Ohhhhhhhh - see I need a photo - never noticed a relay on the 3B oil pump. It always confused me why I couldn't see the relay roller on the 3B where you'd expect to find it. That damn parts system has some holes... but its brilliant to have on your lappy all the same.

[mcandmar]

Not easy to see as the timing belt cover is in the way, idler is mounted on the oil pump and tension is adjusted by rotating the water pump. Crap design IMO.

ABY has the idler on an adjustable mount, much easier to tension correctly. There is also less movement of the belt when the engines running as its tension point is higher.

ABY style oil pump is considerably more expensive from memory, that’s the only downside i can think of. It might be possible to fit a 3B pump or cut the idler mount off it to save a few quid.

[yodasfro]

I've got a stripped 7a I can take some pics of for the archives.

[4WheelDrifter]

Blockwise the 7A uses pretty much all the same gear is the 3B, but has a 82.5mm bore obviously.

[denniselbows]

so in that case you could put a 3b head on a 7a bottom end and you could have a 2.3 turbo engine. may be a couple extra mods. that's if any one wanted to do such a thing

[spink]

so in that case you could put a 3b head on a 7a bottom end and you could have a 2.3 turbo engine. may be a couple extra mods. that's if any one wanted to do such a thing

Mark_H used a 7a block on one of his engines custom pistons etc.More than a couple of extra mods though.

[4WheelDrifter]

so in that case you could put a 3b head on a 7a bottom end and you could have a 2.3 turbo engine. may be a couple extra mods. that's if any one wanted to do such a thing

The whole bottom end isn't really suitable. The block, crank, sump, oil pump would be ok to use. Obviously you'd need custom pistons as the 7A ones are weak for turbo use and the CR is too high, and sort out a suitable head gasket. You'd also need to swap a few things, like the water supply and oil return for the turbo. Nothing major though AFAIK.

[Group_B]

Have another question. Sounds like you could swap heads across bottom ends, but can you also swap manifolds, intake and exhaust, across heads? For example, would an AAN intake/inlet manifold bolt up to a 7a/3b head?

[caterpillar]

the IM and EM will fit right on

[Group_B]

Would it be safe to say that any Audi DOHC I5 manifold would bolt to any Audi DOHC I5 head?

[markrs2]

3B and ABY/AAN/ADU blocks are the same. Just the 3B doesn't have the holes drilled for the cambelt tensioner.

The castings for the later blocks that use the cam tensioner are different in that they have more material in the mounting hole location for the tensioner. If you drill the earlier blocks to accept the tensioner then you will find you only have about 5mm of metal before you drill through to the water jacket.