Jeff your heads are probably like mine, they are the new REV049 heads that Joe
sells and they sport a 12mm plug (I mistakenly told Sam that I had 14mm plugs).
I have dual automotive plugs 3/4" reach.
Cheers
On Thursday, June 29, 2023 at 04:13:43 PM CDT, Jeff York via KRnet
<krnet@list.krnet.org> wrote:
I am not sure what an AA VW cylinder head is either. However, my original GPAS
heads had cracks from the spark plug hole to the valve chamber. The material
there is not much and Ive been told this type of cracking is common.
I had never been happy with the quality of my GPAS heads and decided to have
new heads built byJoe at Revmaster. He is incredibly knowledgeable on the VW
engine and converting it for aircraft use. One look at my new Revmaster heads
made me notice the superior quality. I am not in front of my heads at the
moment and I do not know the spark plug hole size Joe put in my heads, but it
is smaller than what I had from GPAS..
Jeff York
On Thu, Jun 29, 2023 at 2:45 PM Matt Naiva via KRnet <krnet@list.krnet.org>
wrote:
Sam what shape were his calipers? If doing a depth differential and 5-6 mm
error could easily creep in. If he could pinch both surfaces with one tool
his thickness judgment may be right on. That said Great Plains heads are not
thickened for 3/4" reach and they fit a 10mm plug all the time... I
personally like how Mofoco puts secondary plugs in but not how they conduct
business.
Matt
On Wed, Jun 28, 2023 at 9:28 PM Samuel Spanovich via KRnet
<krnet@list.krnet.org> wrote:
Question for all the VW guru’s out there regarding dual spark plug setup,
specifically with AA Volkswagen cylinder heads.
After one year of use with single ignition (the same ones that made it across
the country with me for the gathering last year), I recently took my AA heads
in to get them machined for a second spark plug, in hopes of converting back to
dual ignition. I told the machinist originally to keep the same size plug as
the original spark plug (12mm x 3/4” reach).
However just before the machinist was supposed to perform the work, he informed
me that these particular heads (the AA ones) do not have enough metal up near
the combustion chamber and they are not thick enough to support a 3/4” reach
spark plug (he said he measured the width with calipers, and compared it to an
older MOFOCO cylinder head of mine, and the AA head was supposedly not as
thick.
I asked if it would be possible to machine the second spark plug port for
something smaller, such as a 10mm x 1/2” reach plug. He sounded like it would
physically fit, however he sounded a little hesitant about running that small
of a plug into a fairly powerful engine (~80 HP).
My question is whether or not it would be safe to have this type of setup (1x
spark plug 12mm x 3/4”, and a secondary plug 10mm x 1/2”). I was fairly
certain older VW heads accepted 14mm x 1/2”, so I was a little surprised when
the machinist said he wouldn’t think a 1/2” plug would suffice.
Any input would be greatly appreciated; just trying to make sure I’m not
missing something completely obvious here.
V/R
Sam Spanovich
Sent from my iPhone
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