I think that this is a very old ECHO but not sure. It's too old for the ECHO ID site and the "christmas trees" are not embossed on the engine anywhere but do appear on the label. It appears to be about 21.x cc's. If it's not an old ECHO can anybody ID it ?

Hi Antique,
The engine is a Mac trimmer I beleive made by Echo for mac. Mine has a single unpinned ring and exhust bridge. The port timing is mild, but can be easily increased. Intake has 110 degrees duration, Exhust has 120 degrees duration, Transfers have 90 degrees duration. The fly wheel hub area can easily be removed and used as a timing hub foe EI. Here is the link to mine. It is 21cc.

Dave

http://www.rcuniverse.com/forum/m_31...tm.htm#3186119

what you have is a mculloh.the desighn under the word mod is MC,mcullohs desighn.i posted 2 pics of my echo from a eager beaver so you can see the xmas tree desighn.i had 2 macs but i gave them away.not that they werent any good.the throttle is straight shot to the carb from the start.i just didnt personally like the power to weight ratio.i also didnt want to spend the time porting them when i can just get echos.

It's almost identicle to the one posted by Dave, thanks. This one does not have a bridge in the exhaust port. Measured the porting, exhaust = 130 degrees, intake = 110.

Cut off all of the extra stuff and put on one of RCIGN's ignitions.

Test run with the RCIGN ignition and it turned an APC 15/8 at 7600 rpms with a 24/64 carb.

Did a little work on the exhaust and increased it to 142 degrees. Increased the rpm's to 8000, not bad !

I'll work on the intake porting next.

Hi antique,
I think that you must have a pinned ring, since you lack the bridge. The intake can go to 120 degrees easy. It should help. Maybe you can get into the mid 7k range with a 16x8.

Dave

hello antique,who does your prop hub work.

Ralph Cunningham (RCIGN1) set up the hub for me. I'm also using one of his ignitions. Great guy to deal with, excellent workmanship. There arn't many of these craftsmen left.

Yes it has a pinned ring, and no exhaust bridge.

It does have a fat *** that hangs down well into the intake side. I ground off as much of it as I dared but still holding the ring.

I opened the intake quite a bit from the bottom. Hard to tell how much it increased the duration due to the "eyebrow" shape of the intake port.

Test run with the "24" carb with poor results. Not much gain in rpm's and poor transition.

Changed to a larger carb, a "28". The engine likes that carb a lot ! It now turns the APC 15/8 at 8200 rpm's. Turns an APC 16/6 7900. Very good transition with both props.

Question, This engine has OK compression but not great. By using just the hub I can easily turn it over by hand, I'm sure a new Bowman ring would help. Any idea what gains I can expect from a new ring ?

This one was fun, now to fly it on my test bed airframe.

Hi Antique,
It is running so well, that a new ring may now help much. Go fly it and get rewarded for your efforts. You can always get a bowman ring later. You may have to send thge old ring to him, along with the bore dimention. If you do get a new ring, you will want to lightly break the glaze on the bore with some 400 grit wet or dry sandpaper.

Dave

Your right, I've already gotten more out of this old engine than I expected. I'm going to fly it now and put the ring in it another day. Ran it with no muffler, 8600 rpm's.