<VV> VV - 'valve pre-load'
Hugo at aruncoaches.co.uk
Wed Feb 14 14:31:10 EST 2018
I just found a video on youtube where somebody sets the valves with the engine running, by backing each rocker off in turn till it starts tapping, then slowly tightening it till it goes quiet, then a further quarter turn in. I’ve seen a lot of comments online from people who recommend a half turn or a quarter turn in from zero lash, which is quite a bit less than the ‘official’ amount.
I saw another video where somebody does something similar, opening up the gap till you can hear it tapping, then winding it in till you can feel it misfire. I’m not sure where he ended up (I think a quarter turn in from ‘silent’ once again), but at least you would know what your range was!
From: Bob Helt
Sent: Wednesday, February 14, 2018 5:46 PM
To: Hugo at aruncoaches.co.uk
Subject: Re: Re: <VV> VV - 'valve pre-load'
Andy, I'm with you on twisting the pushrods. It is very touchy and often mis-identified when the twisting gets binding. I prefer to use the pushrod axial movement to determine the zero lash point. Start with the rocker very loose and note the end-to-end axial movement. Tighten the adj nut and note the reduction in axial movement. Keep tightening the nut until all axial movement is gone. That's zero lash
In a message dated 2/14/2018 9:12:09 AM US Mountain Standard Time, virtualvairs at corvair.org writes:
### 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' Hugo, Answer - these are hydraulic lifters and need the pre-load. Andy K. 65 Monza – daily driver (even in wintertime) Wisconsin, USA Virus-free. www.avg.com _______________________________________________ This message was sent by the VirtualVairs mailing list, all copyrights are the property of the writer, please attribute properly. For help, mailto:vv-help at corvair.org? This list sponsored by the Corvair Society of America, http://www.corvair.org/ Post messages to: VirtualVairs at corvair.org Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs Archives: http://www.vv.corvair.org/archive.htm _______________________________________________
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