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What model Onan was the 4.0 for the GMC ? [message #367666]

Mon, 22 November 2021 09:13

hertfordnc

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If i am not mistaken, the Onan's were made just for the GMC but they were an existing product with a lowered intake manifold and different cladding.

Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.

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Re: What model Onan was the 4.0 for the GMC ? [message #367669 is a reply to message #367666]

Mon, 22 November 2021 09:59

Matt Colie

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hertfordnc wrote on Mon, 22 November 2021 10:13

If i am not mistaken, the Onan's were made just for the GMC but they were an existing product with a lowered intake manifold and different cladding.

Dave,

As nearly as I know, they were Power Drawers model 4.0 BF or 6.0 NH. and there were some other numbers, but Power Drawer was the dig change. Both the BF and the NH engines existed prior to and subsequent to the Power Drawer models. Onan did sell Power Drawers to other builders in addition to GM.

An important change in both PD models was the fuel pump and some times the fuel solenoid valve. Many of these engines were set up for gravity feed only.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: What model Onan was the 4.0 for the GMC ? [message #367670 is a reply to message #367666]

Mon, 22 November 2021 12:33

JohnL455

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The original opposed engine came from lawn tractor origins such as the John Deere 318. There it ran up to 3600 RPM governed speed (2 x our 1800 RPM) and likewise had double the rated horsepower. All the details were given by the retired Onan project engineer at a rally seminar (maybe Eau Claire ? A few years back).

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: What model Onan was the 4.0 for the GMC ? [message #367671 is a reply to message #367670]

Mon, 22 November 2021 12:49

hertfordnc

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Location: East NC

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JohnL455 wrote on Mon, 22 November 2021 12:33

The original opposed engine came from lawn tractor origins such as the John Deere 318. There it ran up to 3600 RPM governed speed (2 x our 1800 RPM) and likewise had double the rated horsepower. All the details were given by the retired Onan project engineer at a rally seminar (maybe Eau Claire ? A few years back).

That describes most Onans of all different sizes.

But I'm just exploring some optins.

I have a good working BF which i can make fit into my generator space with a bit of persuasion.

But if the BF is the base of the 4000 power drawer then i wonder if i could swap the externals?

Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.

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Re: What model Onan was the 4.0 for the GMC ? [message #367672 is a reply to message #367671]

Mon, 22 November 2021 13:05

Matt Colie

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hertfordnc wrote on Mon, 22 November 2021 13:49

That describes most Onans of all different sizes.
But I'm just exploring some optins.
I have a good working BF which i can make fit into my generator space with a bit of persuasion.
But if the BF is the base of the 4000 power drawer then i wonder if i could swap the externals?

Dave,
As I understand from doing parts hunting years ago, the engine designation of BF is for all of those engines of that design. As long as it is a BF, it is the same as every other BF except for some external dress. Three things that I do know are special about the PDs are:
1- They draw the cooling air over the engine instead of blow.
2- They are set up for fuel pump and not gravity feed.
3- They have a control board with safeties to enable remote operation.

So, I bet if you can find a Power Drawer with a bad engine, you could swap yours in there.

Matt

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[GMCnet] Re: What model Onan was the 4.0 for the GMC ? [message #367676 is a reply to message #367672]

Mon, 22 November 2021 17:58

James Hupy

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There is one important difference between the BF for tractors and the BF
used in power generators and welders. The governor on the end of the
camshaft for tractors has 5 balls for speed control. Generators and welders
have 10. That makes them much more stable at speed control, which controls
both voltage and frequency an the AC units. Also applies to the NH engines
which are Cast Iron.
Jim Hupy
Salem, Oregon

On Mon, Nov 22, 2021, 11:06 AM Matt Colie wrote:

> hertfordnc wrote on Mon, 22 November 2021 13:49
>> That describes most Onans of all different sizes.
>> But I'm just exploring some optins.
>> I have a good working BF which i can make fit into my generator space
> with a bit of persuasion.
>> But if the BF is the base of the 4000 power drawer then i wonder if i
> could swap the externals?
>
> Dave,
> As I understand from doing parts hunting years ago, the engine designation
> of BF is for all of those engines of that design. As long as it is a BF,
> it is the same as every other BF except for some external dress. Three
> things that I do know are special about the PDs are:
> 1- They draw the cooling air over the engine instead of blow.
> 2- They are set up for fuel pump and not gravity feed.
> 3- They have a control board with safeties to enable remote operation.
>
> So, I bet if you can find a Power Drawer with a bad engine, you could swap
> yours in there.
>
> Matt
> --
> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
> GMCES
> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
> Brakes with Applied Control Arms
> SE Michigan - Near DTW - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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Re: [GMCnet] Re: What model Onan was the 4.0 for the GMC ? [message #367677 is a reply to message #367676]

Mon, 22 November 2021 19:23

Matt Colie

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Registered: March 2007
Location: S.E. Michigan

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James Hupy wrote on Mon, 22 November 2021 18:58

There is one important difference between the BF for tractors and the BF used in power generators and welders. The governor on the end of the camshaft for tractors has 5 balls for speed control. Generators and welders have 10. That makes them much more stable at speed control, which controls both voltage and frequency an the AC units. Also applies to the NH engines which are Cast Iron.
Jim Hupy
Salem, Oregon

Thanks Jim,

I have been into both BF and NH Onans but never far enough to take the governor apart. What you say, makes complete sense with the 1800 operating speed of the generator packages.

Matt

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