Rear Exhaust Gas engines

[Gilbert Pun]

I have a couple of Gas Scale hydro planes by MLBoatworks in the making and still thinking about what engines are best to suit.

With a full modified J&G 29 engine just finished run-in, still considering RCMK or Quickdraw Rear Exhaust engines to put into these big boats as well.

What do you think ? Welcome all comments and recommendations.

 

[Ray Sametz]

What about a CMB?

 

[lohring]

I think it would be tough to beat a Quickdraw Pioneer. An engine with a full sleeve, not open transfer ports is a must for piston wear. A puzzling observation we made with an M&D cylinder on an RCMK crankcase was that the rear exhaust cylinder developed a little less power than it did on a side exhaust crankcase. It might only be experimental error or it could be the orientation of the intake relative to the crankshaft disks. We ran both rear exhaust and side exhaust engines in our SAW boats. The carefully selected (by Quickdraw) side exhaust engine had more power, but we wrote that off to engine to engine variation. I'm sure Quickdraw has the answers from their dyno tests.

Lohring Miller

 

[Todd]

The biggest we can go is a 27.2 setup. 34mm bore with +2 stroke crank in it. We build one 36mm bore 2mm setup but the customer had the pistons he sent us. We had only found one out of two of the pistons were actually good for being able to build the engine.

Todd

Quickdraw

 

[Gilbert Pun]

What about a CMB?

Ray,

I heard good things and bad things about CMB, but a couple of local guys had bad experiences on this engine.

 

[Ray Sametz]

What about a CMB?

Ray,

I heard good things and bad things about CMB, but a couple of local guys had bad experiences on this engine.

All I can say is PM Stu Barr, he has run them.

 

[Stuart Barr]

What about a CMB?

Ray,

I heard good things and bad things about CMB, but a couple of local guys had bad experiences on this engine.

The generation 1 and 2 CMB 27's did have some crank issues. Those have been resolved now.

Stu

 

[Gilbert Pun]

What about a CMB?

Ray,

I heard good things and bad things about CMB, but a couple of local guys had bad experiences on this engine.

The generation 1 and 2 CMB 27's did have some crank issues. Those have been resolved now.

Stu

Since when ?

 

[Ain'tSkered racing]

You should consider a regular exhaust motor with a wrap to center qd pipe will out perform any rear exhaust engine.. just my opinion

 

[GeorgeAlbrecht]

Raul the problem with the side exhaust engines most of the gas scales are not wide enough and you have to make big modifications to the cowling which really hurt the scale look of the boats. A rear exhaust engine is by far the best for the appearance.

 

[Joenagy]

Raul you got me thinking , what are you running for engines?

 

[Steve Seebold]

Since you guys are talking about rear exhaust engines, if anyone's interested, I have a Quickdraw Rear Exhaust Hi Rev 25 that I have never run.

I paid $600.00 for it about 4 years ago and I was told it had been refreshed by Quickdraw just before I got it.

It came with 3 extra pistons and an extra sleeve

If you're interested, I'll take $450.00 for it. Before you ask, it did not come with a pipe or a header.

SOLD IT.

 

[Ray Sametz]

Nice hijack Steve and the wrong forum to boot.

 

[Stuart Barr]

What about a CMB?

Ray,

I heard good things and bad things about CMB, but a couple of local guys had bad experiences on this engine.

The generation 1 and 2 CMB 27's did have some crank issues. Those have been resolved now.

Stu

Since when ?

End of last year I took over the sales and support of the CMB 27's. End of the year, I received all new cranks for these motors and are rebuilding all motors in stock with these. I have over 5 gallons in each of my motors and the cranks still look new.

 

[Hydro Junkie]

Raul the problem with the side exhaust engines most of the gas scales are not wide enough and you have to make big modifications to the cowling which really hurt the scale look of the boats. A rear exhaust engine is by far the best for the appearance.

There are ways to hide the carb and exhaust, just takes a little creativity. Running the carb under the deck works, as does mounting the engine at an angle, just for starters

 

[Steve Seebold]

Nice hijack Steve and the wrong forum to boot.

[/quote

Sorry.

SOLD IT.

 

[Wesleys Custom RC]

I have a rear exhaust M&D in my bubble bud and I love it. I'm building another with a side exhaust and I had to drop the bottom of the hull, raise the deck and slant the engine to get it to fit. It is about $500. cheaper than a rear exhaust. I have seen Stu's CMB run and If they have their problems worked out it will be a screaming fast motor.

 

[Wesleys Custom RC]

I am looking to maybe put a cmb in a new 6 scale. Stu thinks it would be a good match and I trust his judgment. He also recommends a square drive setup. That's the only thing that has me concerned. I'm not too familiar with that kind of setup.

 

[Wesleys Custom RC]

I am looking to maybe put a cmb in a new 6 scale. Stu thinks it would be a good match and I trust his judgment. He also recommends a square drive setup. That's the only thing that has me concerned. I'm not too familiar with that kind of setup.

 

[Wesleys Custom RC]

Can anyone show me a square drive setup. Stu is using that in his gas rigger and I can't quite picture it. I talked to him about getting one of his motors and that is what he recommends.