4 to 4.8 conversion

[clint888]

mark adams recommends this one for 4L chim. It apparently inviolves grinding the crankshaft. Does this weaken it? Does it matter? Anybody had this done??
YES! 4-4.8 NOT 4-4.6

[2 sheds]

The 4.8 uses a reground 4.6 crank and forged pistons, a good suggestion if you want a bit more torque than the 4.6 but don't want to go as far as 5.X, John Eales produces these, so they should be good !
Tim

[shadowninja]

where do i find out more? URL?

[wedg1e]

Forgive me for having borrowed me Julie's blond head for a moment, but how does regrinding the crank give you a capacity increase?
If you made the journals smaller, you'd need a longer conrod to take up the gap, but it would still travel the same stroke, as the crankpin offset from the crank rotational axis is still the same, surely?
Or... is it just that there's so much metal on a 'raw' casting that you can shift the crankpin centres 'outwards' a few mm and effectively increase the crank throw? If so, that hardly counts as a 'regrind' but a 'different' grind...

Ian
Pedantic bastard as ever... ;-)

(Edited to say... perhaps that should read 'forging' and not 'casting'...

>> Edited by wedg1e on Saturday 16th November 15:52

[2 sheds]

Must be an Offset grind.
Tim

[plipton]

Seen this done on air cooled VWs. You offset the grind to give a slightly longer stroke.

[chimburt]

any know what all this does for the charcteristics of the engine then?

presumably an upgrade to 5L running gear would be recommended (preferably before the engine work i guess unless you can afford to do the lot in one go )

>> Edited by chimburt on Thursday 28th November 23:47