Easy Air Filter for Perkins 4108

[Idratherbesailing]

As an owner of a 1991 vintage Perkins 4108 I often looked at the original "bug catcher" air filter (not a filter, just something to keep bugs from being sucked into the engine) and thought that can't be good for the engine - dust on the boat means dust into the engine.

Anyway, I found a K&N filter on their website, and with a little hose and a few parts for a PCV system from the local auto parts store, I rigged this up. I am not putting the model number for the filter since so many Perkins variations are out there, but just take off the old air screen and measure the intake manifold diameter and go to the K&N web site. I drilled the hole in the top of the K&N filter small so the PCV elbow would press fit in and stay without having anything inside to potentially drop off and get in the engine.

50 hours so far and seems to work very well, no oil vapor in the engine room and a little quieter as well as filtered air for the engine. Total cost about $40.00 US. $30 for the K&N filter and $10 for hose, clamps and elbows if you don't already have them in the spare parts bin. If you don't want plastic in the system, you can get the same filter with a metal top and also find "brass" elbows at the local big box store, but since the parts I used are made to work in automobile engine compartments and won't corrode, I went with the plastic and so far it works well.

I've seen other solutions, but this one seems simple and works.

 

[Richard19068]

Is there any chance that would create a little too much positive crankcase ventilation? I like the idea but don't know what the effect of a vacuum on the breather might be. I don't have a Perkins so maybe that is the way they come. I have a Universal m-18 that just has a passive crankcase breather that I put a small filter on that K&N makes for that purpose. It would be nice to route the blow by directly to the intake to reduce engine room fumes if there would be no ill effects from that. Sorry if this is an off the wall question.

 

[Stu Jackson]

Many, many folks have successfully used the K&N filters and have also tapped their oil breather hoses directly to it. I am, of course, most familiar with M25 series Universal engines. C30, C34 and C36 skippers have reported it and written it up, many with pictures on their association websites. Also, IIRC, Maine Sail has ti on his website, or he posted it on our C34 and C36 message boards.

Like this one: http://c34.org/bbs/index.php/topic,4039.msg23025/topicseen.html#msg23025

 

[Idratherbesailing]

The original air "screener" setup ran the hose from the valve cover to the air cleaner just like this. Most of the air cleaner retrofits I have seen for the Perkins have a piece of metal fabricated to fit the intake and receive the hose from the valve cover, then have an air cleaner fitted to that, so the result is the same as I did, just more difficult to make. If your engine is in good shape and not making a lot of blowby into the valve cover, then it should not make any difference to have positive ventilation from the cover. It is not pulling an absolute vacuum, since the hose into the top ends about 1 inch into the top of the air cleaner, several inches above the actual intake manifold, so the vacuum to the valve cover hose is reduced by the air coming into the air cleaner. Positive flow, and some vacuum certainly, but I would not think a tremendous amount. Haven't tested that, though. Just seems to work after 50 hours or so of use.

 

[Richard19068]

Thanks Stu and idratherbesailing. I appreciate the info. Looks like a good project. Particularly with Main Sails addition of something to catch anything extraneous coming out of the breather. May be overkill but better safe than sorry.

 

[Idratherbesailing]

If you use filter material, becareful to secure it

Thanks Stu and idratherbesailing. I appreciate the info. Looks like a good project. Particularly with Main Sails addition of something to catch anything extraneous coming out of the breather. May be overkill but better safe than sorry.

You might want to use some sort of inline filter with secured material. A piece of what may seem to be ok but not very securely fastened material can be sucked into an engine intake manifold in a second. I had a very bad experience with a piece of foam filter material in a homemade air intake system for a diesel generator. It worked fine until the filter got some dirt in it and increased the vacuum level, then a piece of 6 inch foam filter material went down a 1.5 inch pipe into the intake manifold and intake valve...On the possiblity that your filter or oil absorbant material could be sucked into the intake, I would make sure that what I was using would not come astray due to vacuum. Filter materiial and intake valves and pistons do not make a good mix.

I ran the hose straight to the intake as that is what Perkins did originally, and as was said above, many of the current manufacturers also run straight to the intake without any sort of filter...Larger diesel engines generally have some sort of blowby control system. Go to www.boatdiesel.com and do a search and you will see a lot of information.

 

[Richard19068]

Re: If you use filter material, becareful to secure it

"You might want to use some sort of inline filter with secured material. A piece of what may seem to be ok but not very securely fastened material can be sucked into an engine intake manifold in a second."

Absolutely right. I have an idea. Thanks