I shortened the piston in my Black Widow. Good results.

**RknRusty** Tue Feb 07, 2012 12:07 am

I've posted about my woes in other threads about piston resetting. I do all the right stuff(apparently almost all of it) and still have problems. The most recent of which was that it still fit in the bore fine, but the SPI gap had nearly disappeared. No wonder it sounded like a Babe Bee. I couldn't see any dome on the top, so I figured, what the heck... taped it and chucked it in the drill press. I took a sharpie and touched the edge to make about a half millimeter mark, and held a file to it until it disappeared. I used some 1000 grit paper to smooth the edge. The engine revs like a Black Widow should.

nitroairplane Tue Feb 07, 2012 2:01 am

Cool!
Spi and lightened!
Lighter means less vibrations too.

**RknRusty** Tue Feb 07, 2012 2:17 am

My other BW has exactly the same problem. I might add a little more gap just to see what happens. Just from memory, I think I've seen stockers with slightly more than I gave the first one. The only good thing was, with the reduced gap, I got an extra 45 seconds run time. When they run best, I only get 1:50.

A lighter piston may be faster and smoother, but I bet it develops less torque. Some of the wild bench RPM we get with the new short-piston SPI method(Killer Bee, Venom, etc.) may not necessarily translate to stronger flying power. Maybe it helps straight ahead speed, but it may have less guts for pulling high stress aerobatics. Just me guessing and speculating. I tend to do that a lot. Huh...

Kim Tue Feb 07, 2012 3:35 am

You Sir, are a Dangerous Man !!!! As my gaze drifts from your notes, to focus on my covering Black Widow, I swear I can hear a terrified whisper, "NOOOoooooooooo!"

crankbndr Tue Feb 07, 2012 7:12 am

The crazy high RPMs are not good for sport flying, very short fuel runs and the crankcase on my Black Widow Mouse
is already shot.

Kim Tue Feb 07, 2012 8:05 am

crankbndr wrote:The crazy high RPMs are not good for sport flying, very short fuel runs and the crankcase on my Black Widow Mouse
is already shot.

True...and I want most of my stuff for "The Long Haul"...I just have a tough time resisting the urge to "Warp Time with RPM's !"

**RknRusty** Tue Feb 07, 2012 9:36 am

Y'all remember I did it to recover the SPI gap that I lost while resetting the piston rods(I still don't know where it went, as the piston top is still flat). So my BW is running about normal, like new again, not super duper faster.

Adding more gap to an engine that already has the right amount might not help it. If I experiment to find the maximum edge of too much SPI, I'll post my results.

**RknRusty** Tue Feb 07, 2012 9:44 am

Kim wrote:...I just have a tough time resisting the urge to "Warp Time with RPM's !"

Me too. I've souped up everything I've ever owned. I can't help it. It started with Stereo amplifiers and when I got my first car, a '67 Chevy II Nova Super Sport with a 283 V8 and a slip and slide with Power Glide tranny... everything.

Kim Tue Feb 07, 2012 10:05 am

RknRusty wrote: If I experiment to find the maximum edge of too much SPI, I'll post my results.

Yes...please do...and if you get some time and feel like it, maybe pull together a summary of all your experiments to date!

I'll probably HAVE to go "Destructo" on something of mine just to get it out of my system !

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I shortened the piston in my Black Widow. Good results.

I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.

Re: I shortened the piston in my Black Widow. Good results.