Who's got the nice Modified Zenoahs?

[XtremeRcBoats]

Scott Schneider also did a step by step to mod it your own on modelgasboats:
https://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/72-engine-porting

 

[Daniel's Racing]

Problem with all these porting articles is they are old and there is not much relevance to the engines we are modding and porting today. Much of what is shown is completely irrelevent to what we know is proper porting/blueprinting today.

So much more to modding the engines than just the porting.

Today almost all the engines we are building need to have squish band cut and combustion chamber mods to work so the average guy with just a dremel is out of gas.

You will need both a lathe and a mill or have someone who will do those mods for you.

 

[Lay26]

This is so true....a lathe and mill is a must have.

 

[LohringMiller]

I'll admit to being old. However, I think I know a little about engines. My articles were written for beginners. The really essential tool for modifying engines is a dyno. I've encouraged that for years. The other essential tool is research into the latest two stroke thinking. Again, I belong to forums along with the world's leading two stroke developers.

Our industrial engines are crude compared to modern thinking. They were designed to be inexpensive to mass produce. They make a great spec propulsion system for models and have largely replaced nitro engines because of their durability, low initial and operating cost, and reasonable power. There are much more modern designs available, but the low cost Zenoah still dominates.

I have a Monarch 10ee lathe and a Supermax mill. with tooling and a chest of machinist's tools They have machined a lot of engine parts. I've also made tooling to help modify engines. Mark Anderson has all my engine tooling and completed an excellent dyno from my parts. Neither of us sell anything to the hobby. We only hope to improve the experience for others with similar interests.

Lohring Miller

PS I designed and built my first engine in high school. It won two industrial arts prizes.

 

[Mark Anderson]

I will have to disagree partially. A lathe to cut the bottom of the cylinder is a must. Any machine shop could do it for you pretty cheap. I started with the two articles noted and have built many engines using the information from them. They always run with anything comercially available. Is the last little bit of power hiding in the combustion chamber? Maybe. Can you build competitive engines without squish band/chamber mods? Yes. Will you go faster through an understanding of what and why modifications are made? Yes. These engines are no mystery. They have been pretty much maxed out due to design limitations for a long time. The data is out there. I always try to encourage people to learn and do things for themselves. Want racing to be more affordable, stop paying someone to do things that you can learn to do.

 

[Daniel's Racing]

I am talking about building the latest current engines. The Zenoah 36mm 28, 29 and 30 cc and the Zenoah 38mm 320 32, 34 and 35 cc engines.

There is no replacement for displacement is most people's thoughts and they want every CC available.

You are missing the reason completely why it HAS to be done on the latest engines many are running.

The 36 mm we are stroking to 30mm and with 2mm extra it requires that you cut the squish band and combustion chamber. The 30.5 cc is what everyone wants to build.

The 320 is getting stroked extra 2.8mm again this requires squish band and combustion chamber both be cut.

But aside from that the 2mm stroked the 36mm jug runs incredibly better with at least just doing the combustion chamber. Would not consider putting one together even without it being done. I do not know of a single builder that is not doing it.

 

[LohringMiller]

The engine pictured in my Zenoah article was built by Brian Buaas. It had a 36 mm bore and 30 mm stroke with a 55 mm rod. It powered my gas scale boat to the NAMBA gas scale two lap record. There's no new magic in engine modifications. Spacers and/or cylinder machining may be needed to get everything to fit and get a decent squish clearance. There's no way to get the Zenoah combustion chamber volume close to that of a head button engine without adding a head button.

Lohring Miller

 

[Dave Gilles]

I am talking about building the latest current engines. The Zenoah 36mm 28, 29 and 30 cc and the Zenoah 38mm 320 32, 34 and 35 cc engines.

There is no replacement for displacement is most people's thoughts and they want every CC available.

You are missing the reason completely why it HAS to be done on the latest engines many are running.

The 36 mm we are stroking to 30mm and with 2mm extra it requires that you cut the squish band and combustion chamber. The 30.5 cc is what everyone wants to build.

The 320 is getting stroked extra 2.8mm again this requires squish band and combustion chamber both be cut.

But aside from that the 2mm stroked the 36mm jug runs incredibly better with at least just doing the combustion chamber. Would not consider putting one together even without it being done. I do not know of a single builder that is not doing it.

curious if you have any dyno comparisons?

 

[scheibes]

Looking to repower an Aeromarine Sprint Cat with a modified 30 cc Gas Zenoah, Which company do you guys recommend out there?
Thanks in Advance

REDLINE

 

[andy fraser]

Second the redline

 

[LohringMiller]

By the way, there might be a way to modify a Zenoah combustion chamber and still fit the NAMBA G class rules. It involves changing the spark plug. I proposed this idea to the late Jim Allen and he built a version. With a suitable plug body shape you should be able to reduce the chamber volume and get a toroidal combustion chamber form. A surface style plug gap may also be a good idea.

There's no mention of what spark plug should be used in the NAMBA rules and the modification only involves removing material from the cylinder which is allowed. The plug shown was used in a Quickdraw button head, but imagine making the plug body the same shape as the central projection as head button on the Quickdraw head button.

Lohring Miller

 

[Dave Gilles]

By the way, there might be a way to modify a Zenoah combustion chamber and still fit the NAMBA G class rules. It involves changing the spark plug. I proposed this idea to the late Jim Allen and he built a version. With a suitable plug body shape you should be able to reduce the chamber volume and get a toroidal combustion chamber form. A surface style plug gap may also be a good idea.

There's no mention of what spark plug should be used in the NAMBA rules and the modification only involves removing material from the cylinder which is allowed. The plug shown was used in a Quickdraw button head, but imagine making the plug body the same shape as the central projection as head button on the Quickdraw head button.

Lohring Miller

View attachment 333860View attachment 333861View attachment 333862

so are you replacing the factory crush washer with like a thinner copper washer? can you shave the cylinders hump around the spark plug threads also?

Does this actually make any difference on the dyno?

 

[dave roach]

Maston's RC Marine builds a great engine
330-833-6811
Massillon,Oh