VW spark plugs

The place to raise issues, ask questions, swap ideas and discuss anything related to aircraft engineering, maintenance and building.
NB Any opinions expressed in this forum are not necessarily those of LAA Engineering

Moderators: John Dean, Moderator

Post Reply
Dave Unwin
Posts: 12
Joined: Sun Oct 02, 2011 8:53 pm

VW spark plugs

Post by Dave Unwin » Mon Mar 15, 2021 1:32 pm

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

Ian Melville
Posts: 1000
Joined: Mon Feb 11, 2008 7:21 pm

Re: VW spark plugs

Post by Ian Melville » Fri Mar 19, 2021 7:39 am

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.
Ian Melville
032644

User avatar
mikehallam
Posts: 576
Joined: Sun Jan 06, 2008 3:12 pm
Location: West Sussex
Contact:

Re: VW spark plugs

Post by mikehallam » Fri Mar 19, 2021 8:35 am

Diameter !

Neil Spooner
Posts: 20
Joined: Wed Jan 07, 2009 5:22 pm
Location: Colchester, Essex

Re: VW spark plugs

Post by Neil Spooner » Mon May 03, 2021 8:00 am

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.
024282

Post Reply