KI8FR

I did some homie 25s last year and I like what I got out of it and how little work had to go in to it to make it work on my planes. Now I have a Mcculloch 28cc that I was going to convert.

My question is. Does the 28cc have more power then the 25? I did not have to make or put money out for the prop hub and a muffler. It looks as if I will have to for the 28 Mcculloch. The muffler is held on by a spring. And the Shaft will have to be cut down. The threads on the crank are a lot bigger then what the homie has.

For me to put that much work and $ in to this I just want to know if the 28 is better on power then the homie? The homie has a lot of grinding to do on it and the Mccullock you just unbolt the front. Hook up the CH on it and off you go. I make my one fly wheel so that is no big deal. But I do not think I will be able to make the prop hubs I have work on the Mccullock 28.

All info would be nice

Paul

indianatinyengines

That Mac 28 is a good solid reliable engine. I convert and sell as well as use these engines and others all the time. I feel they are equal in quality and are both good engines but yes, you will get more power from the Mac. In my experience, the Mac is very close in power output of the Ryobi 31 while the Homie is closer to a 24cc Poulan. I know the description doesn't help you in exact hp,rpms ect. but I don't have a tach or dyno just user experience. The long shaft version is not a problem in that you cut the shaft off right ahead of the threads. You will need a 7/16 X 20 tpi tap to make the prop hub fit this engine. I would go ahead and do it . You will like this engine having not done one yet. Attached are a few examples of my Mac conversions I have sold. I've converted hundreds of engines of various manufacture over the years so I can probably help you if you need any conversion info. The last pic is of one of my recent adds featuring a few different kinds.

w8ye

My Feedback: (16)

A stock Mac 28 seems to have a little more gusto than a Stock Homelite 25. The Mac has a "24" carb and the Homelite has a "20" carb.

However the Homlites were more responsive to modifications than the Macs.

I've got several of each including Homelite 30's and actually have more Mac 32's than 28's

The Mag is not as good on the Mac as the one on a Homelite. Makes them almost impossible to and start.

I converted a 28 to a 32 and converted a original 32 with C-H ignitions and Walbro 1/2" carbs on both. I used the original mufflers that I gutted out the baffles and put 2 pipes (1/2" hydraulic tubing) outlets in. I used the spring retainer. Use a piano wire hook to take the spring off and put it back on. I have another Dozen whackers setting around in case I need one.

The C-H just bolts on and the timing will be correct. I checked mine with a degree wheel and they were at 28 degrees. I just use a regular R/C battery/switch harness on them.

It's been 10 years but I remember the threads on the long cranks as being 3/8" -24? I just used the C-H hub that slid over the crank and mated with the keyway. I had to cut a piece off the crank that was in front of the threads.

They look like they came from the factory as model airplane engines.

av8tor1977

My Feedback: (6)

indianatinyengines do you have a website?

AV8TOR

KI8FR

very good quetion to ask. I was just about to do that lol

foamcut

My Feedback: (40)

I just googled him and came up with an ebay store.

rollmyown

You can get right around 7500 RPMs from a Mac 28/32 with a M/A classic 18x6 or 18x8 prop. For reference, you can get a bit over 6000 from a 20x6 M/A classic but it runs hotter so I think that 20 inches is a bit too much for a 32cc engine. This is what I am getting and the engines are not yet broken in completely. I do mine somewhat different that most. I don't cut the long shafts. The threads on the end of the shaft are used for a P-47 style prop hub to hold the prop on. Then I have a 1/2" long s/s hex head, 10-32 screw in the end of the shaft to safty the Aluminum hub on, (just in case.) I weld on a 2" square flange around the exhaust port to bolt a homebrew Aluminum muffler on. Getting rid of the big steel muffler alows thinning of the front and back of the cylinder and allows a flat plate firewall mount. I also increase the size of the intake port. I made new carb spacers to rotate the carb so you don't need to reach "through the prop" to adjust the idle screws. My Macs look a lot different now. I tried to post photos but I am not having much luck (and I have posted before). I got the weight down to 4 pounds even, complete with CDI and battery and I am pleased about that. I knocked off about a pound. Macs intrigued me so they became another segment of the hobby. I will still try for photos to show what can be done with these engines. Here is a few photos. I have the magnet 180 degrees from the Woodruff key slot so that the CDI sensor can be on top of an inverted engine. CDI is not included in photo and the sensor is what you see on the bottom of the crankcase. One of the crakcase holes provides a strain relief for the sensor cable, a bolt, a piece of wire, and a tywrap are used.

andernamen

My Feedback: (3)

Just finished my Homelite 25 conversion. With everything including prop, prop hub, velocity stack, carb, magneto and mount, the weight is 4 lbs, 4 ounces. Seems a little too heavy. Is this about normal? I was hoping to put it in a warbird, but at that weight, I don't think I'll be able to.

Ralphbf

My Feedback: (27)

With a mag the weight is right on.

Most War Birds need extra nose weight because the radial engines they were designed for
were very heavy.

For $75.00 you can loose the weight of the flywheel and coil.

What plane are you thinking of putting this engine in?

KI8FR

That is what I did with my homie. put cdi on it from CH ignition on it. It will bring it down to 3 lbs with the bat and modual. and you will get about 200 to 300 more RPBs out of it.

rollmyown Were did you get your prop hub. I like what you did with it and would like to do the same thing.

Paul

foamcut

My Feedback: (40)

Rollmyown,

Your mods to the Mac engine are really well done. I'm going to copy a few of your suggestions.

Thanks for sharing your work.

rollmyown

Foamcut, you are welcome. Thats why I posted the pictures. I found that welding a flange onto the exhaust cylinder was possible. Fitting a Aluminum flange does take time. I made a 1/8" steel plate drilling template. I use the Aluminum welding rods and a Mapp gas torch. Mapp gas is much better than Propane. I am going to use the same idea on a few 25cc Poulans. The reason I decided to try welding a flange on the Macs is bercause the Mac muffler is heavy and big and it is very tough to get a seal at the exhaust port on the cylinder, so oil leaks out and makes a mess. The flywheels are also pretty heavy on a Mac, eliminating it helped me get down to 4 pounds.

KI8FR

Rollmyown::::: Were did you get your prop hub. I like what you did with it and would like to do the same thing.

Paul

foamcut

My Feedback: (40)

rollmyown,

I was guessing that you had TIG welded the exhaust flange onto the cylinder. Apparently you've found a way to make those aluminum gas welding rods work. I had thought that the exhaust temperature would eventually soften any material deposited. Since you're using MAPP gas you're using a much higher temperature during the weld. Are you using any other methods like a special flux or pre-heating the cylinder? Your method is a real problem solver for the exhaust on this engine, the exhaust on a weedie 18cc, and the intake on a Poulan 46.

Thanks again

andernamen

My Feedback: (3)

Ralph,

I have an EI system that I was saving for my Homey 45 cc. That engine though, is less weight sensitive and I think I'll use it on the 25 cc. I have a Hellcat ARF 70" wingspan I'd like to use this engine in. Just need to get a prop hub that will work with EI. CH I believe has them.

tkg

My Feedback: (1)

We drill a 5/16 hole vertically on both sides of the exhaust port, from the top fin to the bottom fin. Take a piece of 5/16 rod and tap it sideways. The drop the rod in the hole and use it like a toggle bolt to hold on the muffler.

av8tor1977

My Feedback: (6)

Neat idea Terry...

AV8TOR

KI8FR

Now that is a grate idea.

Now I just need some info on a prop hub. Help. lol

foamcut

My Feedback: (40)

TKG,

Great idea for the muffler mount...thanks for sharing.

captinjohn

tkg: Can you post a photo of how the 5/16 rods hold muffler on? Do you use a gasket also or sealer on joint? Thanks Capt,n[:-]

KI8FR

It is nice to see there is more then one way to put the muffler on. and I love the idea about welding on the flang. I will be giveing that a try.

But one of the big things that I Need to know about is the prop hup. HELP me out here lol

What is it that you all did about geting a prop hup?
Paul

tkg

My Feedback: (1)

Call CH Electronics 307 857 6897 and order PN 103 a Mac timing kit. 39.95

indianatinyengines

To answer the questions a couple of you asked. I'm currently only on ebay but will probably be selling on this site in the future. You can also contact me thru pm if you need a specific engine converted. or are interested in buying direct.

Just for giggles, i'm attaching a few of a 56cc Homie chainsaw I just converted for 1/3 scale use for a customer.

rollmyown

KI8FR,
Sorry about the slow response. The prop hub is actually two pieces. Scott Baldridge made the front part of the Prop Hub assembly, the part that has the 7/16 shaft matching rear threads and the Knurling to drive the prop. I made the rear part to fill the space the Flywheel vacated. Of course you need a Lathe to make this piece. I just have a Taig Lathe with patience and perserverance. Cutting the slot for the Woodruff key is a challenge without a Mill or ?, but I do have a drill press. As I stated, I located the Magnet, from Radio Shack, a small 1/8" diameter Earth Magnet, 180 degrees from the Woodruff slot in a drilled hole in the rear, close to the outside diameter of the Magnet hub (rear Part). I rest of the hole has a plastic plug to keep the magnet in place. There is a center punch mark on the magnet hub so you know where the magnet is to set up the timing. Scott Baldridge probably has the dimensions I gave him to make the prop hubs. I might be the first to set up a long shaft Mac like this. I'll see if I can sketch these parts and post them in this thread. By the way, the P-47 prop nut is made from Fortal, an Aluminum alloy about equal to 7075, (good strength for internal threads) and the rear is drilled out to save weight. It looks like a revolver cylinder from the rear.

rollmyown

foamcut,
sorry about the slow resonse again, as you all know things come up. I got a new Mac 28cc, never run, engine off **** real cheap and decided to experiment with it. I found that the cylinder material held up well while welding. No tendency to soften or melt and not difficult to weld either. I clean all welding surfaces as though I was going to eat off of them, then wire brush them with a stainless steel brush for good measure. The stainless steel is suppose to react somehow. The Mapp gas allows you to do the welding process rather quickly compared to Propane. (Propane will work for smaller parts, but is definitely not hot enough for a cylinder.) I have been using these rods for a few years now, it does require a learning period. I leave the weld material high enough so that I can grind it flush after cooling, on my belt sander. I have done two cylinders so far and will do a few more. I am real happy with how they turned out myself. The 28cc is a short shaft engine, (it had a long blower shaft with no threads on the end). I also tried my intake port on it first. I ran this cylinder on a 32cc crancase and it ran great, it has good response and sounds like a big glo engine at wide open throttle. I will sketch the port enlargement also for those that wish to see it. As I said before, the intake port seemed small compared to the exhaust port and the cylinder transfers. I suggest welding Aluminum scrap metal before tackling parts of your engines. Note that different alloys of Aluminum will act differently when using these rods, probably some will be harder to work with than a cylinder. Burned up and scored cylinders if you can find them would be excellent practice.