changing engines... what else?

[erick herdt]

I have an old tired PC Bruin, that I am 80% sure I am gonna replace the engine on, as the Onan 24hp, has some serious internal issues (valve seats eating their way into the block, and they're seating crooked, so it's F**ed at best. It has an upgraded Cat 5CP pump (not the old Daishun), and a Sutorbilt 4MP blower.

I am looking at either a 24hp Kohler water cooled engine or a 27 hp air cooled Kohler.

I like the idea of running a water cooled engine (cooler and quieter), but I like the idea of more power spinning everything.

Since I am gonna have to do some cutting and welding of stuff to get the new engine in place, what else would ya suggest I do to get extra "grooviness" out of the machine.


If you were me, and money is a SERIOUS issue, what would ya do to tweak just a tad bit more performance out of it.

An undersized blower pulley, to increase RPM's?

Turn the max RPM's on the engine up a tad, for more OOMPH??

Talk to me, guru's. Help me to see the light.

THANKS,
Erick

 

[Duane Oxley]

Eric...

Personally, I'd tear the system apart and build it on another, less- cluttered frame. And I'd reduce the complication of the design as much as possible. I'm not familiar with that particular model enough to recommend specifics, though.

My suggestion regarding over-driving a blower is always to increase pulley size on the motor. That doesn't reduce belt traction, but instead increases it a bit. And when you overdrive, do it at 15%. If the motor is running at 3,200 RPM, then 15% in addition results in 3,680, which is actually a modest increase over the recommended 3,600 that most blowers are spec'd at.

I've overdriven as high as 20%, BTW, on one system I made in 2000.

 

[Greenie]

I'll take that 27hp air cooled any day over that 24hp water cooled.

Quieter, I don't know who started that rumor?

Noise off that motor is a drop in the pan for what you will get with an over driven #4 blower, I'd be focusing on that.

With a glided wand, you can run that blower at 15-16"hg all day long.

That 27 is a tried and true motor, and it will make some wicked heat for a HX system.

 

[Bob Savage]

The noise of an over-driven #45 can be quieted way down (not to mention the increased air flow by reducing restriction on the discharge side of the blower), by using an over sized silencer and piping (recommend 4" ID inlet and outlet) with sound attenuation, such as Stoddard makes.

On my slide-in, my #45 blower and 20 HP Onan (Linimar) is set up using this arrangement.

I agree with Duane - keep the belt traction as much as possible. I have an 8" pulley on my 20 HP Onan, with a 7" pulley on the #45 blower, using a single "B" belt. This belt will usually last for 3 years of almost daily use.

Pulley alignment needs to be as close to perfect as possible for a smooth running setup.

Let us know know how it turns out.

 

[Matt King]

Greenie's right. Most of your TM noise if from the blower. The engine recommendation is right on too... get the 27hp motor. Less parts, more power.