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What are the differences between a regular and a K47 airbox?

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
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Like the title says, what are the differences between a regular and a K47 airbox?
can the K47 be had from any 97-2000 f code that is equipped? or are the 99-00 different?
 
There are two air filters in auto parts listings.

One is a larger diameter than the other. The large one barely fits in the air box in my 98. The cover is held open some. The diameter difference is about 1/2" or so.
 
does the k47 have a prefilter on it? i know when i got my Wix heavy duty flat panel filter it had a pre-filter that was some form of black foam.
 
iamdave0887 said:
does the k47 have a prefilter on it? i know when i got my Wix heavy duty flat panel filter it had a pre-filter that was some form of black foam.
Click to expand...

I have purchased both the 'regular' filter, and the 'severe duty' filter from the dealer. The 'severe duty' appears to be a regular filter with a nylon pre-filter surrounding it. It is rather restrictive. I ran one for several months, and noticed my fuel economy sink by a couple miles per gallon. Also, when accelerating or under heavy load, it would produce black smoke, which is indicative of insufficient air, or too much fuel.

I then switched over to a K&N, and the black smoke went completely away. I also picked up a couple miles per gallon. However, the testing reports indicate that K&N lets a lot of silica (dirt) into the engine.

I have since read all the reports, including the famous "Spicer" test reports, and have gone back to the stock GM filter. It appears to have the best balance between efficiency and air flow.

The K47 housing is simply a 'little' bit bigger to allow mounting of the 'severe duty' filter. I don't think you'll find much of a difference in air flow, if any.

If I were changing my air filter housings, I would consider the following:

1) Retrofit a LARGE filter, from a larger truck (Dmax, Pstroke, Cummins, etc.), to increase the overall CFM capacity of the filtration system. Having a much BIGGER filter will help a lot, since you'll have increased efficiency AND airflow. I would experiment with the largest filter that can be easily found and figure out how to shoehorn it in there.

2) I would build my own cold air box out of sheet steel.

3) I would buy side vents (ala ChevyDave) and put real air vents in the fenders to allow for a much shorter distance from outside air to the filter.

I would NOT suck air from the engine bay - it is too hot in summer. I would NOT put a K&N filter in - it lets too much dirt by. I would NOT spend massive amounts on the cold air intakes out there.

-Rob
 
Hi Rob,

Thanks for your post- these steps sound like a cost efficient way to improve air flow. IIRC, somewhere (maybe at the other site) someone had issues about using side vents due to patterns of air flow.

At high speeds, does air flowing from front-to-rear over the vent create some form of aerodynamic drag, which in turn increases resistance to the engine sucking in cold air? Perhaps this is a minor thing, that wouldn't impact the engine's ability to draw air at all.

Another thought..Would reversing the side vent to **scoop** air into the engine compartment be better? Would this bring too much cold air into the engine during cold months?

Just some thoughts.. It would be great to hear any feedback about the side vents.

Jon

TurboTahoe said:
3) I would buy side vents (ala ChevyDave) and put real air vents in the fenders to allow for a much shorter distance from outside air to the filter.

-Rob
Click to expand...
 
If I were pinched for time and dollars, I would just buy a used K47 housing from a member here or off ebay or off car-parts.com and then put a stock filter in. It's a pretty good compromise of cool air and airflow. That's assuming you have the flat airbox setup. I can definitely tell that the K47 airbox flows more air on the Tahoe. Granted, I am using the 'seat of pant' dyno, but it definitely helped in my experience.

-Rob :)
 
chi2 said:
Hi Rob,

Thanks for your post- these steps sound like a cost efficient way to improve air flow. IIRC, somewhere (maybe at the other site) someone had issues about using side vents due to patterns of air flow.

At high speeds, does air flowing from front-to-rear over the vent create some form of aerodynamic drag, which in turn increases resistance to the engine sucking in cold air? Perhaps this is a minor thing, that wouldn't impact the engine's ability to draw air at all.

Another thought..Would reversing the side vent to **scoop** air into the engine compartment be better? Would this bring too much cold air into the engine during cold months?

Just some thoughts.. It would be great to hear any feedback about the side vents.

Jon
Click to expand...

My understanding is that you might get some problems with airflow with certain shapes of vents, especially if at speed you create a vacuum, or pressure difference, by the way the vent is shaped. I would think you need some testing to determine this. You could do a poor-man's windtunnel with a leaf blower and some streamers to see what happens at speed, or just put the streamers on and run on the freeway (probably with someone else driving so you can see what's happening...)

Might be fun, or just a big hassle.

-Rob :)
 
So do you mean use a K47 with the bigger filter that is meant for the K47 (w/o foam wrap of course), or use the smaller filter that is meant for the stock airbox IN the K47 (for better/more even filter "loading" of dirt)

I am a huge fan of paper filters in donaldson housings (farm equipment!) so iwill be going K47.

actually, did donaldson build the K47? I know they built the airbox in my old man's 98 gasser.
 
GM Guy said:
So do you mean use a K47 with the bigger filter that is meant for the K47 (w/o foam wrap of course), or use the smaller filter that is meant for the stock airbox IN the K47 (for better/more even filter "loading" of dirt)

I am a huge fan of paper filters in donaldson housings (farm equipment!) so iwill be going K47.

actually, did donaldson build the K47? I know they built the airbox in my old man's 98 gasser.
Click to expand...
Yes, the K47 housing will fit EITHER filter. There's not a whole lot of room for airflow on the 'severe duty' filter, in my view. The 'smaller filter' really isn't any smaller - it's just that the 'severe duty' filter has the pre-filter wrapped around it.

Listen, we tend to get kinda crazy about filtration - The stock cylindrical filter does FINE. I think that most people with them will say the same.

I recommend a free flow exhaust, and GET RID of the stock downpipe. A new crossover would be good too, but watch out for snapping off the bolts that attach the crossover to the manifold. If you have an S engine, then OPEN UP THE INTAKE. Use a dremel tool, or a short blade in a jigsaw to cut out the excess webbing. Better yet, swap to a F intake. That's a little bit more effort, but worth it.

-Rob :)
 
I have a big ol f-code in a 15K GVWR rig, so intake will be fine.

Here is the plan

SS Diesel (Heart Throb) 4" system w/ 3 inch downpipe and 2.25" crossover, all stainless.
K47 airbox w/ standard duty filter for max area around filter for better loading of pleats.

GM8 turbo w/ either stock or sring wastegate
 
I have not looked into it too much. i would like to keep it GM, and similar to stock (don't want to make it a big gooseneck puller, just decent size BP)

Is the a-team the single, Mitsubitsi non-wastegated turbo, or is it something else?
 
So the filter made for the K47 is the severe service and will come foam wrapped? So one will need to order the standard filter and put it in the K47?
 
TurboTahoe said:
If I were pinched for time and dollars, I would just buy a used K47 housing from a member here or off ebay or off car-parts.com and then put a stock filter in. It's a pretty good compromise of cool air and airflow. That's assuming you have the flat airbox setup. I can definitely tell that the K47 airbox flows more air on the Tahoe. Granted, I am using the 'seat of pant' dyno, but it definitely helped in my experience.

-Rob :)
Click to expand...


This is exactly what I did and I'm very happy with the results.
 
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