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Super Tigre S.61 Roundhead

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Old 04-13-2009, 09:57 PM
  #1
rainedave
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Default Super Tigre S.61 Roundhead

This is a used engine that I rebuilt. I was very lucky to find a NIP ABC P/L set for it; it was originally ringed. I also installed new bearings. The rear bearing is an oddball Y-17 (17x32x8) that Boca stocks. I also put in a new rod and gaskets.

It's a good strong engine. It turned within 22rpm of my OS .61FSR which did 12,964 with the stock muffler. I ran the ST with a new Silent muffler.

Temp: 56°
Powermaster GMA 5/22
K&B 1L plug
APC 11x7
12,942 w/Silent muffler
1.39hp
7.93lbs. static thrust

David
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Old 04-14-2009, 12:49 PM
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Default RE: Super Tigre S.61 Roundhead

Sweet, looks like I may have to keep my Magnum/Thunder Tiger GP65 it runs 13,500 with an MA 11X7. But it prefers a little higher nitro to run best. And Magnum Fuels 15% made the most power. I think I have about $7.00 in it.
Nice one Dave you engine monger you.
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Old 04-14-2009, 03:49 PM
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Default RE: Super Tigre S.61 Roundhead

There are so many older, used engines out there that it's a shame not to rescue them.

I did some preliminary runs with a Mac's muffled pipe. The header is at the stock length. I'll cut a 1/4" off and try again.

Same fuel and prop as before
13,761
1.67hp
8.97lbs. static thrust

This pipe is way, way too loud to run any more on my patio. I'll have to wait until the weekend when I can set up down at the local school.

David
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Old 04-14-2009, 06:14 PM
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Default RE: Super Tigre S.61 Roundhead

I have a similar header but the head pipe is not quite the right size and shape for it. I haven't put much effort into it yet. So many engines so little time.
I found the local auto parts store is a good place to find silicone or high temp hose for the connector. [8D]
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Old 04-14-2009, 06:23 PM
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Default RE: Super Tigre S.61 Roundhead

I won a whole slew of those Hatori reusable clamps off the auction site. They are a little hard to wiggle into place, but the silicone connector will not slip.

One interesting thing about this engine. When I first installed the new ABC P/L set it hardly had any pinch. After about eight short runs it now has a very tight, squeaky pinch. From the very first run I have had it set just rich of peak (using the fuel tubing pinch method). I never let it four cycle at all. Dar might be happy to know that.

David
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Old 04-16-2009, 03:10 PM
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Default RE: Super Tigre S.61 Roundhead

A bit more testing today. I cut 3/8" off the header and got a fair increase.

Temp: 67°
Powermaster GMA 5/22
K&B 1L plug
APC 11x7
14,297
1.87hp
9.68lbs. static thrust

The engine is continuing to break in, so part of the increase is due to that, and part due to the shorter header. This is getting close to the maximum rated hp. I will cut off one more 1/4" and test again. If I get close to 14,500 I'll stop there and be happy. My goal is not to get the absolute maximum performance; this is an old engine. What's interesting is that you can hear it stepping up on the pipe well before the throttle is wide open. I don't have a lot of experience with pipes, so I don't know if this is typical. It's very loud, on the verge of being uncomfortable.

David
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