Gravely 566 exhaust/muffler - - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 5 Old 10-24-2019, 03:20 AM Thread Starter
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Gravely 566 exhaust/muffler

I'm going to renew the muffler on my Gravely and have a question regarding the connection between the exhaust manifold and the cylinder. As far as I can see from various Gravely/Kohler part lists, part suppliers etc is the exhaust manifold a slightly bent pipe with a flange, see picture below.
On my Gravely with a Kohler engine type K301S, spec. nr. 47601d, however, the manifold consists of a 1 inch (I believe at least) threaded pipe screwed into the cylinder, see photo. There is no flange and the pipe fits ok albeit with some play such that some exhaust blow out between the pipe and the cylinder. I have not yet dismounted the muffler, just planning the best way to attach a new "silent" and better looking one. Also, as I cannot just pull out the pipe from the cylinder, it appears there is a thread in the cylinder as well.
My questions are therefore:
1. What is the normal connection
2. Is the threaded version I appear to have a valid/possible option
3. If I use the flange version, what's the thread size of the bolts. I measured something like 8mm so my best guess is 5/16" UNC. Is this correct. The threads in the cylinder looks ok but I may have to "clean" them with a screw tap
4. Exhaust pipes on a Gravely/Kohler seems to use threads. Is it just a normal 1" UNC thread or something special. The reason for my question is that if I buy Gravely parts from the US, I may have to buy the tools as well as inch thread cutting tools are difficult, if not impossible, to buy in Germany or Sweden
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post #2 of 5 Old 10-24-2019, 07:36 AM
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Re: Gravely 566 exhaust/muffler

I'm not expert on kohlers, but here goes. I *think* kohler engines were set up to use either a flange with a couple of bolts, or 1" NPT pipe threaded in.

The K301 on my comm12 has a flange with a couple of cap screws. The K181 on my mountaineer has holes for a flange, but has pipe threaded in.

The bottom pic is of an exhaust flange for a gravely L model, not a kohler. If you want to set yours up with a flange, you'll need to find the correct part for a kohler. There seem to be some available on ebay, but you'll likely have to do some measuring to make sure.

The IPL for what I think is your tractor calls for a threaded pipe.

I suspect your easiest path is to remove the existing exhaust, and carefully unscrew the pipe that's in there. Figure out what size it is, like 1" pipe, and clean out the threads with the right size tap. Then thread in a new pipe to a new muffler.

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post #3 of 5 Old 10-24-2019, 12:07 PM
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Re: Gravely 566 exhaust/muffler

I wouldn't worry to much about replacing the pipe as it'll be more headache than it's worth. I would just cut the muffler off right where the pipe meets the muffler, and then install a Cub Cadet/Kohler style muffler like below. Make some sort of mount to support the end of the muffler, and then you can cut a portion of the tip off, split it, and then reclamp it to the end of the muffler to direct the exhaust in any way that you like.


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post #4 of 5 Old 10-24-2019, 02:09 PM Thread Starter
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Thanks for your inputs. Regarding the IPL, you probably mean part number 10865P1.

The pipe part is not in the best condition and in any case, the nut is missing (108866P1 Nut Conduit; 1" Pipe).

In the IPL I have, the thread size is not mentioned you could be right it's a 1" NPT. I will check here it somebody can measure it.

It's probably no problem to dismount the pipe because the fitting is rather loose. Probably due to the missing nut.

I'm waiting from dismounting it just now because, as it is, I have to cut the pipe and afterwards I have to drive the machine a few hundred yards without a muffler to the garage of the village blacksmith. He's welding much better than me. My neighbors would be very happy.
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post #5 of 5 Old 10-27-2019, 08:30 AM Thread Starter
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I'm really frustrated.

While I can get hold of a 1" NPT threaded pipe in V2A or V4A in Germany for a price of less than 5$, it's impossible to get hold of the corresponding locking nut (part number 108866P1 in the IPL I guess).

I can find BSPT (British standard) threaded nuts but US NPT standard seems to be extremely rare if non existing in Europe.

Does anybody have an idea where to get it?

I can probably order it from the US but the total cost increase a lot. As for the Cub Cadet muffler, shipping to Europe easily doubles the prize tag visible on e.g. Amazon (i.e. shipping and custom duty and VAT) so if I can avoid it, I rather buy European.
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