Mac engine parts

[lawn dart]

I'm looking for 90 hp jugs for my mac engine, don't know if there still available? also looking for parts to install electric start. Thanks Dave

[Gyro28866]

R & D Engineering - Red Smith 469-688-7016 cell
The price will scare the crap out of ya.
I just got some on Ebay last week, I am excited for them to get here, so I can replace my blown jug on my 90 Mac also.
After I get them here, I might consider selling one? will have to see.
The electric start, yo can find an old post here, where one bwas built for Marion Springer. There was pics with it also.

[Gyro28866]

here are the pics

[Gyro28866]

more pics,
hope this helps

[JEFF TIPTON]

Link to article

http://www.rotaryforum.com/forum/showthread.php?t=21640

[lawn dart]

If you do decide to sell one let me know or if you see others for sale. thanks, Dave 920- 420-3106

[Twowingnut]

I am building a Mac 72 ( and spare ) for a Ragwing Mini Pits, and I am looking for a few pointers... the first engine had a crack in the #4 bearing cage, in looking for a replacement, Red told me that we no longer use them... the bearing cage assembly was the number one cause of engine failure in the mac... moving forward, I also found out that the mechanical fuel pump is also not recommended, two mukuni's now are recommended... my question is regarding the source of vacuum drive, the rotory valve area has a viable access port on the lower side of the engine ( which could drive the two pumps ( if the rotory intake for the cylinders is not working... then there is no need to supply any fuel to the engine ) but what of the old mechanical pump housing, it is a source of low pressure vacuum, do we mill off the housing and plug it, or do we tap into it and use it as a source of low pressue vacuum for the second fuel pump ?
Since there is not much information out there regarding Mc Culloch engines, you folks are the last of the Mac guys ( and gal's ), most of you knows what works, but most of all... what not to do... just looking for pointers from the ones who know it best...

Curtis Parks

[Rick Whittridge]

Curtis, Here is where you should get your vacuum source from for the two pumps. Take the mech pump off, pull the rod out & seal, then hacksaw off the mount. Tap a 1/16 X 27 pipe hole & plug the hole. Hose bib fitting is 1/8 X 27 pipe.

[Twowingnut]

Thanks Rick... I have seen some photos of this mod on engines before, but the pictures left a lot of guess work ( too much room for error when guessing )... the mod should be easy enough... Thought has gone into carbs, since there is no oil sump on this engine, one is really not restricted as to which way to mount it...I have a Stromberg NA-S3A1 carb that came off a champ, this provides both throttle as well as fuel cut off controlls... If I invert this engine, and installed the up draft carb, hopefully the engine would not know the difference... thanks again for the tip, maybe next weekend I will be doing some drilling...

Curtis Parks

[Rick Whittridge]

Curtis, This is the carb that is used on the Mac. Holley 1940. I have these Modified Carbs in stock as well as K&N Filters.

[Twowingnut]

Dear Rick,

Thanks for the photos of the Holley, I have seen the posts regarding the 1920, and the 1940 carbs, both seem to work very well as a proven system for the Mac.. my concern is in regard to the engine cowling on a bi-plane... not many bips out there look good with a hood scoop... so to stream line the cowling, I am trying to go inverted ( the engine, not the plane... )...

I still have quite a way to go on building the airframe, seems that the engines are going together faster than the actual aircraft project...

The plan when it is all together, to test run it for many hours before I even thing of taking the thing off the ground...

Thanks again for your advise, and I am still thinking CDI, but the weight of the battery and charging system, would make a UL into an LSA... I still have pleanty of time to weigh these options...

Thanks again, and I wish everyone a Merry Christmas...

Curtis Parks

[Gyro28866]

Curtis;
I have only flown with Mac engines on my personal gyro's.
I fought the Magnito, and then converted to the CDI from Rick.
That is the ONLY WAY to go!!!
Once the engine/carb/ie: mag is set up correctly. On the third or forth pull and she fires up and runs smooth.
Oh, by the way Rick Whittridge is the resident EXPERT here for the Macs and parts and info that you will need.

"The plan when it is all together, to test run it for many hours before I even thing of taking the thing off the ground... "That is most likely not a good idea, for long ground runs on the Mac. you are going to build a lot of heat and that is not good on the engine. Talk to Rick about this also
Ricks #: 937-878-2598
if he does not answer, leave him a message, he WILL return your call.

[Twowingnut]

Thanks Dave & Rick,

With so little information out there regarding Macs, it's good to know that there are still people out there who are very knowledgable about what works best... CDI, Alternator, voltage regulator and small battery, maybe LSA is the best way to go on this project...

I had seen a couple of Macs, many years ago in a surplus store in Roswell... I thought they were very cool back then, now that I am rebuilding a couple... I still think they are very cool... thanks again for proving that the mighty mac is not just a throw away target engine, but a useful engine for light aircraft...

Curtis Parks

[Twowingnut]

Mac Engine Mod, the old mechanical fuel pump housing removed, the quarter inch plunger hole has been tapped out to 5/16 X 18 threads and the plug will be sealed below the hex... The accessory case hose bibs are on back order, once I get them, I will work on that portion of the vaccum mod...

The question comes to mind of the fuel burn per hour... the MQM-36 was rated as one hour flight duration on five gallons of fuel ( @ Max throttle setting and airspeed just below 300 MPH ) my question is, what is the average fuel burn per hour at cruise... this way I would know what to expect...

Thanks

Curtis Parks

[Gyro28866]

On my gyrocopter, I have a 5 gallon fuel tank. When I had the 72 installed I had, depending on how I pushed it, got 57 to 63 minutes in the air. With the 90 installed she goes quiet in 53 minutes.
I would strongly suggest dumping the mag and going with a CDI from Rick. Starting is much easier and better idle.
If you go onto Ebay, there are always a book on the Mac.
search: mcculloch drone
there are two listings currently Item number: 370538573360