Spark Plugs

Scott Hersha · #1 04-22-2020, 07:21 PM

Question:
I need a spark plug with a shorter height from the cylinder to the top of the plug where the harness attaches. My RV4 doesn?t have a whole lot of room (O-360-A1A). I just replaced all the baffle seals, as well as installing a new ignition harness, and there is very little clearance from the top of the harness where it attaches to the plug, and the cowling in the cheeked cowl. I?ve heard that Tempest plugs are a little shorter, but have been unable to get any external dimension details from either Champion or Tempest. I am currently running Champion REM40E?s. They were new less than a year ago by the previous owner, and in checking the internal resistance, it ranges from 1300 to 2700 ohms. I?ve heard that Tempest UREM37BY?s are not as tall. I?m not all that concerned about the slightly cooler plug (higher CHT) of the -37BY?s. I?m not unhappy with the performance of the Champion -40E?s, I?m just looking for more headroom. I haven?t been able to find a reference for external spark plug dimensions. If anyone knows the external height dimension, from cylinder to spark plug harness connect, please let me know.

Thanks,

If I have to buy new plugs, I?ll probably pick Tempest.

n82rb · #2 04-22-2020, 07:46 PM

i have tempest in my warrior, i will measure one in the morning for you.

bob burns
RV-4 N82RB

Isaac · #3 04-22-2020, 08:01 PM

The UREM37BY?s are about 1/2" shorter that the UREM38E. I installed Tempest UREM37BY's in my RV6 with O-360 A1A engine to get better clearance between the plug and the baffles. It was hard to get a socket on the top rear plugs. Had to use a crow's foot with torque wrench when reinstalling. The UREM37BY's solved that problem. I haven't noticed any change in CHT's since installing them.

Full Throttle · #4 04-22-2020, 09:14 PM

You can always switch to auto plugs. More heat ranges and a lot shorter.

Scott Hersha · #5 04-23-2020, 07:29 AM

Can the Slick/Champion type harness be adapted to use an auto plug? I have a SureFly on the left and a Slick on the right.

Isaac · #6 04-23-2020, 11:25 AM

G3i has a do it yourself option and I think they will do it for you but at more expense.

http://g3ignition.com/magmod.html

Full Throttle · #7 04-23-2020, 11:36 AM

Maybe rocketbob has a salutation for changing mag wires to auto plugs. If he does, I'm sure it will work well.

Full Throttle · #8 04-23-2020, 11:42 AM

Maybe rocketbob has a recommendation for changing mag wires to auto plugs. If he does, I'm sure it will work well.

Scott Hersha · #9 04-23-2020, 12:35 PM

Thanks. I?ll look into the G3i option, or order a set of Tempest UREM37BY?s.

CDN · #10 04-24-2020, 01:49 PM

I have one Bendix mag with the G3i auto harness mod with a SDS CPI on the other side and I run NGK BR8ES on all 12 plugs. I have over 400 hours on this setup and just swap new plugs in at every annual rather than have to clean/rotate aviation style plugs. It will get you the clearance you need plus less/cheaper maintenance in the long run.

The instructions from G3i are very easy to follow. I have purchased the 18mm to 14mm spark plug hole adapters from several sources for different projects over the years and the best ones I've found (and the ones I'm currently using) were purchased from Ross at SDS. G3i likely sells them as well but I have no experience with them.

I did the mag mod myself but I ended up buying some parts directly from G3i, rubber grommets and the rivets they recommend IIRC. The shipping to Canada cost me about 4 times what the parts did.