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 >> -- >> KRnet mailing list >> KRnet@list.krnet.org >> https://list.krnet.org/mailman/listinfo/krnet >> > > > -- > 'Any sufficiently advanced technology is indistinguishable from magic’. > Arthur C Clarke > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet >
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