Air filters

RACER X #99 · #1 (**permalink**) 01-03-2003, 05:24 AM

Been noticing lately a lot of guys especially the guys with the big motors running those little air filters from K&N. I know they flow better than the Stellings but all the charts I read say they are way too small for my 351 so how can they possibly work on a 427?
All the guys that run open track with us have the large 14-16 inch filters. Both the BB and sb guys all run the big filter.
I have deceided to lower my engine about two inches so I can run one of those big filters. I hope it is worth the effort.
Anybody out there switched to a big filter and noticed the difference?

Cranky

Clois Harlan · #2 (**permalink**) 01-03-2003, 06:01 AM

Cranky,

When I was dyno testing my 428 last spring I took several air filters. One was the K & N big filter. I made a pull with the filter without any oil in the filter. Then I used the Red oil that K&N provides and made another pull. I lost about 4 hp when I added the oil. Compared to my 3" air filter (that fits under my hood) I lost about 7 or 8 hp. when I put on the big filter without any oil added.

I was running a 750 holley, the air temp was about 80 degree and there was about 88% humidity. In fact it started raining before I finished all my dyno time. However, we did not make any carb adjustments while I was testing the air filters.

Before I got on the dyno one of our local (Chevy) Nascar trucks had been on the dyno testing several sizes of K&N air filters. His tests also showed a loss of hp when he added the oil to his filters and also showed no advantage in hp over his 4" Moroso air filter.

Just a little input.

RACER X #99 · #3 (**permalink**) 01-03-2003, 06:22 AM

Clois,
I plan on running the 14X 3" paper filter and changing it every year as I only put about 1,500 miles a year on the motor.
I guess the K&N is good for those who don't want to buy a new filter all the time.

Cranky

Ron61 · #4 (**permalink**) 01-03-2003, 06:47 AM

Cranky,

I run the 15" length, 8" width, and 3" height K&N filter on my 351 and I really noticed a difference in it and the one for show that is 21" long and has the Cobra top. But I don't see much difference in the K&N and any other good filter that size that I have tried. That size just happens to fit under my hood well with plenty of clearance.

Ron

coyled · #5 (**permalink**) 01-03-2003, 08:52 AM

Cranky, Too small of an air filter can reduce power. In this case, bigger is always better. The reason a lot of guys may not see a difference from small to big, is because their motor does not have the claimed hp. scott

BANDIT 1 · #6 (**permalink**) 01-06-2003, 07:12 PM

Alot of the people that are running single 4bbl carbs are using the K&N E-3505 oval air filter. The filter height is only 2" and the filter flows around 390 cfm. There is a 4" version that will flow around 775 cfm, however it is too tall for most Big Block Cobra's. I was able to have some custom 3" K&N filters made that will flow around 600 cfm. I run the 3" filter unless I think the other car/bike is really fast, then I will take my chance with no filter at all.