QRC Style Muffler

Ken Cook wrote:There was a aluminum shim that went under the muffler first. In addition, the hex portion on some of those mufflers are not always equal. I have had some a few thousands wider than others. Bernie sold or used to sell a exhaust timing shim that fit the base of the cylinder, this would work for your application not only to make the muffler tight but it would also eliminate any SPI if present.

Ken, thanks for sharing that. I didn't know there was such a feature that would eliminate or minimize SPI to make the muffling more effective for the earlier engines. Mufflers I have are for the later non-SPI Cox engines. I can say that back in the early 1970's, I bought a Tatone muffler for my Babe Bee. I thought that it lost power because of the exhaust gas restrictions through its exhaust pipe. Little did I know that through muffling the SPI caused recirculation of the inert exhaust gases, which diluted the air-fuel mixture charge.

At least in the later mufflers for the non-SPI engines, I've found that if you have a spring starter, then the ring shim may not be needed. My Ranger engine that I picked up recently had a loose muffler. (This is the engine with a plain white Dragonfly tank and non-throttling muffler - used on Cox RC RTF's.) That slack was taken up when I restored the spring starter it once had. You'll notice on my Ranger that the muffler is now lifted up by the thickness of the spring starter with its wire loop around the base of the cylinder area.

And the card that the muffler was packed in shows to use the spacer ring when a starter spring isn't used. In fact, there was also a spacer ring in the kit muffler for spacing a Tee Dee venturi/spray bar up and forward to clear the same muffler.
This is also carried over to the Medallion/Tee Dee .09. I can acan the back of the one I just got if anyone wants to see it.

My QRC muffler also rotates.  I thought that it came stock from Cox with a throttle muffler like the Dragonfly.  It doesn't have the hex on the base.  I thought that was what the RC part of QRC meant, and that was the main difference with the QZ.

I'm less familiar with the QRC as I never bought one. The Ranger's muffler has an octal shaped base. As shown in my photo, the engine's orientation to the tank is incorrect, because I can rotate this particular muffler. If the engine is mounted to the side, sidewinder fashion, the tank ridge bumps out enough to lock the muffler into position.

If your muffler doesn't have such an octal base but has a machined aluminum sleeve with a round base that fits around the muffler with two smaller slits, one on each side exposing the cylinder exhaust between 1/3rd and 1/2 the width of the exhaust port, then it may be a rotating ring throttle muffler that someone replaced its original muffler with, especially noticeable by it freely rotating. There will be a "C" ring around a groove in the aluminum, which allows an RC pushrod to be connected to it. If there is a groove but no "C" ring, then it is missing.

Thanks for sharing everyone, I don't have a spacer but the QRC should have the starter spring anyway so that will fix it.

Thanks again Canso07.

Just checking my QRC that's NIB and it has the octagon base muffler and spacer ring because it has the Snap Starter Spring and Cam.
I have another QRC that may be older that has the low drag starter spring and of course no spacer under the octagon muffler.
FYI...………….

If this muffler is mounted on engines without the spring starter, the top black ring is to be placed with its lip on its internal diameter pointing upwards. Thus the mounting dimension is increased and the muffler will sit fixed between the crankcase and the lowermost fin on the cylinder. This was also explained in the product manual as far as I remember.

Good read so far. I like the comment that balogh made with flipping the 'ring' around for engines without a spring. After looking at the picture again, it makes sense, and I can see it.

+1 for Balough. That beats rolling my own spacer ring.
Here is the back of the NOS .09 muffler I just got from theBay.

I think if lacking the spacer ring, one can do as Balough pointed out and flip the washer like black muffler top cover upside down, which will help to take up the gap that the spacer or spring starter wire fills. However, I don't think that part was the intented to be flipped over.

All the RTF's that came with a muffled reed valve engine also came with a snap or cam starter. If one is picking up these engines used, no telling what situation may come up. I picked up a used Testors McCoy .35 Red Head, which one of the previous owners installed the piston and head backwards. The little fence dam or baffle was forward toward the exhaust port instead of closer to the intake bypass port. It was also missing the nylon crank throw spacer that prevents the crankshaft connecting rod pin from digging into the engine's backplate.

And, deviating a little off topic, 30 years ago I picked up 2 brand new Fuji .099S-II RC engines in the box over the counter from Hobby Shack in Fountain Valley, CA with aluminum millings inside the crankcase. Apparently someone got in a hurry and didn't bother to wash or blow the crankcases out before assembly at the Fuji factory. I cleaned those and averted a disaster. From that point whether new or used, I refrain from turning over the crank until I get a good look inside by partial disassembly. You never know what you may find.

One option is, if you don't want to install a starter spring, to just cut the necessary portion off a "junk" spring and snap that around the groove on cylinder base on the crankcase. Many of us have a few springs that are either corroded or wound up too tight, or both. It would be the correct material in the correct size and shape