Big twin breather question

[32 coupe]

After a rebuild and about 10 hours running time at about 30% load I saw that the engine was 'weeping" oil everywhere. I never understood how the "reed valve" breather could work on the twin so I removed it made a blank plate and tapped the plate and the intake manifold and piped them together. Slowed down the weeping but did not stop it. I knew I would have to remove the flywheels to paint so I guess I will replace the Indian gaskets with some I cut from good gasket material and see if I can stop it.

Anyway the question is do you guys see anything wrong with the "crankcase vacume" set up I made ?

[dieselgman]

I cannot comment on the breather mod per se from personal experience, but the concept looks to be viable. This is basically what was done with later engines. This is ineffective if your rings are leaking a lot of compression. Getting a read on crankcase vacuum can be a good diagnostic. Increase loading to help with ring seating.

dieselgman

[BruceM]

Hi 32coupe,

I'm not so clear about this for the twin, but here's my thoughts:

I think you need  a larger diameter (1 inch ID?) to the intake manifold. Your current system will require too much pressure in the crankcase to force the air through that skinny line to the intake. With the twin's cylinders moving in opposition, there aren't the big pressure pulses of the single, but obviously there is enough blow by to pressurize your crank if you've got oil weeping out.

 A check valve is also needed, so that some vacuum can be created. A line with no check valve won't make a vacuum. (At least once the vent line is increased.)  I've had good luck with a brass water check valve with the spring removed, in a vertical position, as someone here once recommended (Ronmar?).  I just vent mine outside via 1" heater hose.  The vacuum really is effective in keeping oil in.

But take this all with a block of salt because I have no twin and so am just thinking out loud.

Best Wishes,
Bruce

  

[Horsepoor]

Back in 2005 when I first ran my GTC twin, I had some oil weeping issues too. I quickly identified paint on the reed vavle and a slightly bent thin metal plate. Easily fixed with some cleaning and straightening. Might it not be easier to just replace the reed valve to original specs? Here is link for the $12.75 part http://www.generatorsales.com/order/oil_fill_elbow.asp?page=Oil_Fill_Elbow

[honda lee]

What size pulley are you running on your st head? Your engine wheels are 20 in are they not? I am thinking of the same setup but with a Lima head. Thank lee

[honda lee]

What rpm are you running engine?

[Horsepoor]

If your question is directed to me, I have 2005 GTC 20/2 down rated from 1000 rpm to 800 rpm. I have an ST 15 gen head that I've gone through and cleaned up (I.e. Glyptol, timken bearings, western style bridge rectifier, etc).

Down rating the diesel makes about 16 to 17 HP and I can get a maximum sustained output of 11,200 watts. I really like the lower speed beacuse my peak afternoon loads are around 8000 to 9000 watts with everything running. Think hurricane diaster recovery operations, two AC units (2 ton & 2.5 ton - downstairs & upstairs), well pump for horses, electric hot water heater, washing machine, electric dryer, etc. The lower speed keeps the GTC diesel loaded up to around 80% - perfect for us.

Late at night, when all the heavy AMP stuff is shut off, I get by with a Metro 6/1 running at 800 rpm driving an ST 7.5 head. This gives me preformance close to an 8/1 and I can run a little more 4000 watts for brief periods. This step up runs night time house lighting, TV, several refrigerators cycling on and off, and one Trane SEER 19 AC unit and only ONE. Amazingly, the Metro will usually start and run the well pump too but this somewhat dependant upon how many refrigraators just happen to cycling on: Thus I now shut the well pump off at night. This leaves the Metro running at night with around a 3000 watt load. This setup works for me.

[32 coupe]

After much looking, thinking and testing I may have a different view.
I measured crankcase pressure at 0. My guage would not show any pressure on the case and about 5 inches of vac. with a pulse on the intake manifold.
All of the Indian gaskets were soaked in oil by me before assembly so the weeping MAY be the gaskets just letting go of the extra oil. Before I tear it down again I will run some more and see. I also think I may have had a little too much oil in the engine on the initial run.

Still with that said I still don't get the original reed valve idea. My single (Metro 6/1) works perfect and I can hear the valve working when it is running. With the 2 pistons working the way they do I just don't understand how the reed valve could ever create negative case pressure.

After 10 hours run time yesterday I drained the oil and checked the rod bearings. They look just like they did when I put it together so all is good !
 You guys are the best ! Thanks for the input.

Gary

[BruceM]

I think your pressure/vac gauge measurements make sense for a twin, after some thought. The intake manifold pulses are the only source of vacuum you've got, since the piston movement is opposing. Without a check valve, it's going to be pulse negative from the intake and  zero pressure otherwise, as the case is vented to the room.  With a check valve in the line, you should get some vacuum building up in the case, and no more gasket leaks.  A dirty air filter would help with the negative pressure.