Mark, We'll I thought I might an answer, but probably not. I researched this for my Great Plains heads and found there was a different reach on the plugs top vs bottom and had emailed Steve Bennett a couple years ago. But it looks like I am using 14mm spark plugs not 10 mm. Figured I would forward the message any way as you might find out that the reach on the plugs is different as well. The Bosch reference might get you closer to an answer.
Spark Plugs for Cylinder Heads --- original message from 2011--- Rob: We use a Bosch 7904 or cross over equivalent Steve Bennett Great Plains Aircraft From: Robert7721 <robert7721 at aol.com> List-Post: krnet@list.krnet.org Date: July 19, 2011 12:59:16 PM CDT To: info at greatplainsas.com Subject: Spark Plug for Cylinder Heads Steve, I received the new cylinder heads and have installed them on my airplane. Much thanks for expediting. I do have a question on spark plugs for the top side. I ended up with both the bottoms and the tops machined for the 14mm plugs. That is not a problem. However it looks like the reach on the top side spark plugs should closer to a 0.7" vs a 0.5" that I have currently. I went to a automotive parts store - but without a make and model automobile to put it on, they were not much help. What automotive spark plug should I get to work with the longer reach and which also matches your spark plug adapter? I've got 0.5" reach spark plugs in the heads for now, and it seems to be running fine at the moment. Thanks, Rob Schmitt N1852Z KR2S -----Original Message----- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of Mark Langford via KRnet Sent: Sunday, June 14, 2015 11:25 AM To: KRnet Cc: Mark Langford Subject: KR> GPASC dual-plug 10mm plugs? I'm about to install a pair of Great Plains dual-plug heads on my 2180cc VW engine. Anybody know what make and model of 10mm plugs folks are using for the secondary plugs? I'm tearing the engine down anyway, since I found a broken cylinder stud yesterday, among other things. I noticed the broken stud while working on a new "performance" website for N891JF (http://www.n56ml.com/n891jf/performance/), and noticed the CHT for cylinder #4 wasn't even registering. After the stud broke, the nut backed off and the CHT ring was just floating around in space. See http://www.n56ml.com/n891jf/performance/ for that shot. I'm thinking Megajolt or Megasquirt to fire these plugs. Given that I have injector bosses on the intakes, I may just have to go Megasquirt. Either of these will manage spark based on load and MAP, so advancing the ignition at high altitudes could yield some real efficiency increases. Megajolt's not very expensive either...something like $170 for the controller, and it uses inexpensive Ford EDIS components that came on millions of 90's Ford cars and trucks. Don't forget my spark plug question. Plug wire info would be good too. Thanks, -- Mark Langford ML at N56ML.com http://www.n56ml.com _______________________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org please see other KRnet info at http://www.krnet.org/info.html see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options
