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VW spark plugs
Posted: Mon Mar 15, 2021 1:32 pm
by Dave Unwin
Hi All, planning on drilling the second set of plug holes in my new heads and was wondering what the received wisdom was re 12mm long or short-reach plugs? The current heads use 14mm plugs top and bottom, but I think 12mm on the bottom is probably better. Cheers, Dave
Re: VW spark plugs
Posted: Fri Mar 19, 2021 7:39 am
by Ian Melville
I always though the reach used was determined by the head thickness at the plug hole?
Exposed threads in the chamber are a no-no as it can prevent plug removal.
Re: VW spark plugs
Posted: Fri Mar 19, 2021 8:35 am
by mikehallam
Diameter !
Re: VW spark plugs
Posted: Mon May 03, 2021 8:00 am
by Neil Spooner
The original light weight heads have a thinner casting so by the time you have machined deep enough to get to a flat seat for the plug gasket you are looking at a short or medium reach plug. You don’t want bare threads exposed in the head otherwise carbon will build up on the thread and cause problems with plug removal. The later thick casting heavy heads will have enough material for a long reach plug. In both cases use a 10 or 12mm plug. The less material that you remove the better.
Try to ensure that you don’t drill through close to the valves otherwise head cracking is an issue.