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Old 07-11-2009, 07:55   #1
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Location: New Orleans
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Air Filter for Perkins 4.108

I would like to fit an air filter to my 4.108 Perkins that currently has the stock dome-shaped "bug strainer" type of non-filter. I thought there was a thread about this, but I can't find it with the search.

I think I can get a filter that will work from S&B or K&N filters, then I just have to make a short piece to hook up the breather tube to the intake stub.

Has anyone done this, if so, could you share details? It would help if anyone could tell me the O.D. of the intake where the filter fits down on the intake, so I could order the filter without having to make an 80 mile trip to the boat.


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Old 07-11-2009, 09:01   #2
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Walker Air Sep (small) $449
The Walker Airsep does three things very well: it
serves as a cleanable/washable air filter (Note,
Perkins marine diesel engines don't really have an
air filter), the Walker Airsep recycles the unburned
fuel back into the oil pan via the dipstick, and
finally an Airsep reduces the noise by about 5
decibels. People are amazed but most noise from a
four-cylinder diesel comes from the air intake, not from
the exhaust. We have sold hundreds of these units for
use on Perkins diesels, small generators, CAT engines,
etc. We now have the model appropriate for a Perkins
4108 or a small generator specially priced at just
$419! See Foley Tech Tip # 20, How to Install a Walker
Air Sep System
for more details.

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Old 08-11-2009, 05:00   #3
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Looking for something cheaper than the Walker Airsep

I appreciate the reply, and the Walker solution will work, but I was looking to make something for a LOT less than $500. The basic filters are around $40-$50, and can be cleaned and reused many times. There was a thread on this board, I think, in the past where this had been done by several people, I am hoping one of them will chime in.
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Old 09-11-2009, 07:20   #4
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This is from my post on the thread Air Filter on Diesel back in summer of 08.
I looked up the information on my K&N filter. FYI I have a 1983 4-108 with the heat exchanger as part of the exaust manifold but I imagine that this combination would work on other 4-108's also since the manual shows the same type of dome air cleaner on other 4-108's (measure twice cut once). Sorry to say I could not find my original sales reciept and the numbers on the unit (FO22A6) don't seem to mean anything to the search engine at the K&N site. I'm pretty sure it is an RC-650 however as it looks the same and has the correct dimensions. I attached the filter to the engine with a piece of exaust tubing 4" long 2 1/4" ID 2 3/8" OD. The centerline of my engine vent hose connection hole is drilled 1 3/4" from the bottom of the tube (best fit up for my layout). I cut slits around the bottom of the pipe with a hack saw to match the original dome filter then hose clamped it in place. I treaded a hose adapter into the hole I drilled and sealed it with some fuel resistant sealant (from NAPA I think). As K&N says I streched it slightly to fit during installation on the pipe and since the one I bought has an offset I turned it to be over the top of the engine then tightened the hose clamps. If other's have a different layout more space, less space etc. the K&N site has a nice search engine for looking up filters by dimension and type (round, oval, etc.). I did this same modification on a 30 HP Universal diesel on my last boat 12 years ago and found it easy to match a K&N filter to the dimensions (had to use a parts book back then). Hope this helps.
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Old 12-11-2009, 15:57   #5
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Thanks, that is the post I was looking for. I appreciate the effort.
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perkins, perkins 4.108

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