Engine Blocks? Single cam -vs- Twin cam

[fro]

Are the bottom ends the same? Wikipedia lists them both as Alpha series G4EK engines, and I've seen listings fr both motors using the same head gasket set... so is the bottom end the same?

And does that then mean the gearboxes are interchangeable?

[Crazy Dave]

Don't know how different the bottom end are but the gearboxes are interchangeable. Slightly higher diff ratio in the single cam according to some but not others wtf:. I reckon the bottom ends would be a bit different but probably not much.

[Whitey]

The main (only?) difference is the pistons, the twin cam pistons have a higher crown and relief for two inlet valves.

[Trevor]

Dave mentioned that some people think the gearbox is different between the single/twin cam motors.

Is this corrent, does anyone know for sure, which one would be better?

Main reason I am asking is due to the possiblity of buying a twin cam auto, and bolting it to a single cam gearbox?

Edit:
One other thing, what about ECUs? I know the single/twin cam ECUs are different, but is their a difference between the manual/auto ECUs?

[HMCA]

Ok

I will need to confirm this with the workshop manual

The final drive and output shafts are the same according to the parts manual, There was talk about the single cams being different here but when we checked the original SOHC g/box final drive to that of the brand new twin cam box we put in the car they were the same.

There is no difference with the ECU between Auto and Manual.

Cheers Mick

[Trevor]

Thanks for that Mick.