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Engine basics => Engine set up tips => Topic started by: Bill Heher on June 15, 2014, 05:31:33 PM

Title: Muffler pressure ( sort of )
Post by: Bill Heher on June 15, 2014, 05:31:33 PM

I picked up a fully built Cutlass at Delta Park, grabbed an OS 30 last trip home to slap in it and see why the previous owner gave up on it.

He had the tank set up for muffler pressure, but no muffler on hand. The engine is a converted R/C model, so it has a tapped blind hole in the center of the exhaust port. I had a barbed banjo fitting from an old solenoid valve, and it threaded into the hole.

I drilled the hole through to expose it to the exhaust stream, cleaned up the threads with a tap, and installed the fitting. 

See Pics- I'll follow up with a flight report if it quits raining.

Title: Re: Muffler pressure ( sort of )
Post by: Jim Thomerson on June 15, 2014, 07:10:36 PM

I did something similar with a Fox 35.  I used a small piece of tin bolted to the holes above and below the exhaust.  It blocked off about 1/4 of the exhaust opening and had a pressure tap in the blocked of part.  It worked very well.

Title: Re: Muffler pressure ( sort of )
Post by: Bill Heher on June 16, 2014, 08:10:34 AM

Thanks Jim,

I had a strap on OS muffler, but it didn't like it, ran hot as blazes. I figured it will generate enough pressure to keep positive fuel flow.

Title: Re: Muffler pressure ( sort of )
Post by: FLOYD CARTER on June 16, 2014, 10:59:07 AM

In the days when we ran Torp 29 engines, the K&Bs had a threaded boss in the backplate used for a fuel tank.  We drilled through with a #80 drill and threaded a pressure fitting there. That worked well for tank pressure, and didn't depend on using a muffler (mostly ran without mufflers in those days)

Floyd