On 31 May 2023, at 9:59 am, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

Here's a couple of pictures. As you can see one only need to increase the size by 1/8" or so.

I had easy access because I had decided against putting radiator there in the narrow RV-4 cowl.

Finn
On 5/29/2023 12:47 AM, Stephen Izett stephen.izett@gmail.com wrote:

Thanks Finn

I had similar ideas. 

Because of the position of the main coolant radiator I have limited room for getting in there.

Cheers

Steve

On 29 May 2023, at 12:23 pm, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

About 1-1/16". Just measure the OD of your socket.

On the lower holes (Leading) I used a round (ball) carbide bit. Maybe 1" diameter.
On the upper ones I put in a spark plug with the socket on it and traced the outline on the "eyebrow" and below.
I had an 1" OD flat-bottomed carbide "bit".
Used in electric drill motor. Alum is soft. Just went real slow speed. Not as difficult as I had anticipated.
I picked up those (used) carbide bits at an outside vendor at Sun'n'Fun decades ago. No clue where to get them now.

Obviously would get prettier result with rotor housings in a mill -- only an option with disassembled engine. I also considered a holesaw with a machined bushing in the hole as a guide, but not practical as don't have a lathe to make the bushing and a proper OD holesaw, although 1-1/8" could work.

Finn

On 5/28/2023 10:28 PM, Stephen Izett stephen.izett@gmail.com wrote:

Hi Finn

Thanks for the information re plugs and gaps.

How did you end up grinding the housings and how much did you remove?

I’ve ground a few plug sockets down but they are so thin they break.

Cheers

Steve Izett

On 29 May 2023, at 10:11 am, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

Talked to Tracy.
He's looking for gap in the 0.03 to 0.035" range, but just installed BR10EIX which I think comes with 0.048" (approx) from manufacturer, I think. He just eyed the gaps in the new plugs and called it close enough.

He also ran the stock RX-7 plugs in his Renesis until he ran out of his stock of them.

So it doesn't seem all that critical.

Alter grinding the rotor housings to make room for socket over the AR2502 plugs, I did a short flight (16 mins) today with the old cleaned trailing plugs and two new AR2592 plugs gapped to 0.030". Seems I gained at least 100 RPM on takeoff and climbout.

BTW, measured gap on four AR2592 new plugs and it varied from 0.024 to 0.030. Supposed to be 0.025" from manufacturer. Moral of story is you need to check/set gap on new plugs (where possible).

Probably all common knowledge to you all but new data to me.

Finn


On 5/25/2023 9:13 AM, Finn Lassen finn.lassen@verizon.net wrote:

For those of you who use the AR2592 spark plug in the Renesis, do you use the 0.6mm gap the plug comes with? I bought 8 of them some years ago.

I've been using the stock plugs (RE7A and RE9B) for maybe 100 hours by now. Experienced a brief 200 RPM drop on last takeoff. Wondering if it's time to change plugs. Or re-gap the stock plugs to what?

What can I learn by looking at plugs?

Best way to clean them?

Finn

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