Onan 782cc generator engine install into 520H

[Anvil 6]

Yesterday I was given an Onan RV Emerald Plus gas generator with a 782cc twin engine, working but very crusty. Would this engine possibly fit in a 520H? If very different, would any of the engine parts be interchangable...heads, crank, block with the 520? Considering the generator RPM is 1800 and I'm guessing this is the lowest RPM utilized for maximum output of the 5K generator, could this engine withstand the normal RPM used on the 520? I read the compression is 7:1, same as the tractor.

[lynnmor 6,775]

Generators are usually run at a lower RPM for noise reasons.  The generator head is wired to give the proper 60 cycle current at that lower RPM.

 

In order to run at 3600 RPM, you will need to change out the governor.  The speed should not be an issue, the engines are essentially the same.  Probably the biggest problem will be the crankshaft drive end, the generator may require a taper and the tractor a straight end.

Edited January 19, 2019 by lynnmor

[Achto 26,548]

52 minutes ago, Anvil said:

Considering the generator RPM is 1800 and I'm guessing this is the lowest RPM utilized for maximum output of the 5K generator,

 

Running at 1800RPMs tells me that the generator is a 4 pole gen.1800 RPMs would = a frequency of 60Hz from a 4 pole gen, this is the frequency used for electricity in the US. Europe prefers to run at a frequency of 50Hz which would again change the engine speed. If the generator was a 2 pole then the engine speed would have been set to 3600RPMs to achieve 60Hz. Nuff schooling.

 

Issue that you will most likely have-

1 The PTO end of the engine will most likely have a tapered shaft instead of a strait keyed shaft.

2 No thrust bearing for a mechanical PTO clutch.

3 Governor setting

 

1 Taper to keyed shaft adapters can be purchased, about $60on Ebay

2 Switch to electric PTO clutch.

3 Figure out your gov settings

 

 

 

.

 

Edited January 19, 2019 by Achto

[Anvil 6]

Thank you all for your responses. I had an idea the end of the crank might be different. The engine on the 520 experienced the typical valve seat problem and did more damage than I was hoping for. I wondered if the crank from the 520 could be put in the Generator block and transfer all the stuff over, only using the block, pistons, heads, etc from the generator? At this point I haven't taken the generator apart as it does work. If the block is compatible then it would be worth while to tear it down and investigate further.

Thanks again for your assistance.

[Achto 26,548]

4 minutes ago, Anvil said:

I wondered if the crank from the 520 could be put in the Generator block and transfer all the stuff over, only using the block, pistons, heads, etc from the generator?

 

This would be a course of action if the parts will interchange. You might still need to switch to an electric PTO as there might not be provisions for a trust bearing in the generator block.

Edited January 19, 2019 by Achto

[bc.gold 3,399]

1800 rpm governor uses ten flyweights, five must be removed to achieve and maintain 3600 rpm,During reassembly the plastic collar must be in the 3:00 o'clock position. I/m using a generator engine in my Simplicity 9020, swapped the crank and oil pan.

 

The generator engine has no provision for an oil filter but these Onans have a capacity for a large volume of oil so regular oil changes should keep your engine happy. On a side note the generator block has been pre-machined for the filter base, I never investigated beyond that in what it would involve to install the filter base.

 

 

 

Edited January 20, 2019 by bcgold

[Anvil 6]

Thank you all for your input. I had no idea this would get so involved. I have not torn down the 520 engine to its "bones" yet but prior to the valve seat condition the engine was quiet and ran very well. The thurst bearing on the PTO end of the crank, is that machined into the 520 block and not the generator block? My intention was to basically tear down both engines to the bare blocks and switch over all the usable 520 "stuff" into the generator block. The generator actually has an oil filter. I think this would be the least complicated of all options. Your thoughts??? 

 

[bc.gold 3,399]

44 minutes ago, Anvil said:

Thank you all for your input. I had no idea this would get so involved. I have not torn down the 520 engine to its "bones" yet but prior to the valve seat condition the engine was quiet and ran very well. The thurst bearing on the PTO end of the crank, is that machined into the 520 block and not the generator block? My intention was to basically tear down both engines to the bare blocks and switch over all the usable 520 "stuff" into the generator block. The generator actually has an oil filter. I think this would be the least complicated of all options. Your thoughts??? 

 

Your later production engine probably has a plastic thrust bearing with shims to adjust end play, connecting rods do not use bearing inserts so if the crank has been turned make sure your using the same rods that were fitted to it.

 

Onan also used several different camshaft profiles which maybe identified by the numbers embossed into the cam, some cams will not have the lobe for the mechanical fuel pump ground, the lump in the casting it present but not finished.

 

 

 

Edited January 20, 2019 by bcgold