<VV> VV - 'valve pre-load'

Hugo Miller Hugo at aruncoaches.co.uk
Wed Feb 14 11:05:46 EST 2018

### Ok, I’m with it now – I didn’t realise these had hydraulic lifters. As I said, I did once come across a similar method for determining valve TIMING when I rebuilt an old British AEC commercial diesel engine some years ago (as used in the old London double-deck buses). Most diesels gave opening and closing points for both valves, but the only cam timing info I could find for this engine was to open up the valve clearances to .021” instead of the running clearance of .014”, then turn the camshaft till the relevant pushrod was “stiff to turn”. I found this completely meaningless, as it was so vague, and in practice I found that the pushrod was ‘stiff’ over quite a large range of cam rotation. Then the penny dropped. I realised that what they were TRYING to say was that this was the point at which the valve would begin to open at the correct running clearance. So I set the gaps back to .014”, put a dial gauge on one of the valves, & timed it when the valve started to move. It was the sweetest running engine you ever heard. Why couldn’t they just say that was what they meant? 

From: Kinzelman, Andy 
Sent: Wednesday, February 14, 2018 1:57 PM
To: Hugo at aruncoaches.co.uk 
Subject: VV - 'valve pre-load'


Answer - these are hydraulic lifters and need the pre-load.

Andy K.

65 Monza – daily driver (even in wintertime)

Wisconsin, USA


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