How restrictive is an original air cleaner?

[Talkwrench]

I have the original 4 BBl air cleaner on my 360 and Im wondering how restrictive it is? Is there much benefit to change it to a 14 x 2" or 14 x 3 " aftermarket type, is there pros and cons ?

[Supercuda]

The original air cleaners for the high-performance engines were pretty well thought-out. If you are dealing with the dual snorkel air cleaner, the only drawback was the height of the air cleaner element, which was a little low. The basic design was good, and won't severely limit performance until you are flowing some pretty serious air. The unsilenced, open-element styles used on the fresh-air cars were better, and the bases of those were actually engineered to help control the airflow, improving the quality of the air charge. A taller air filter in one of those is the best.

[Talkwrench]

I would be great IF I had a dual snorkel unfortunately its only a single...   

[Road_Runner]

 

I've got an original 1973 340 single snorkel air cleaner to go on mine when I switch to a 4 bbl.  I'm anxious to hear the responses you get on this.

Later, Jim

[Aussie Challenger]

I will be fitting a dual snorkel filter when I fit my new engine with a cold air tubes attached, I prefer to collect the outside cooler air as it is more dense producing more power. I will also be adapting a taller filter element.   

[Supercuda]

Unfortunately, the single-snorkel units are more about silence than airflow. Using a taller element will cause a gap around the housing. This isn't pretty, but does increase airflow. It works much like flipping the lid over did on the GM cars. Although the air isn't cooled, it is more air. On a stock or nearly stock 318, you can even get away with using the single-snorkel with fresh air ducted through the snorkel, with no real downside. It flows plenty for this. For a "stealthy" way to get more air, without obvious hacking of the air cleaner, you can cut out the bottom of the housing, outside the filter element channel. More air, and the housing passes a quick visual inspection.

[Aussie Challenger]

You can fit a taller element and use a different cover or modify like I will be doing to close that gap up, it might take a little work but can be done.   

[Road_Runner]

Unfortunately, the single-snorkel units are more about silence than airflow. Using a taller element will cause a gap around the housing. This isn't pretty, but does increase airflow. It works much like flipping the lid over did on the GM cars. Although the air isn't cooled, it is more air. On a stock or nearly stock 318, you can even get away with using the single-snorkel with fresh air ducted through the snorkel, with no real downside. It flows plenty for this. For a "stealthy" way to get more air, without obvious hacking of the air cleaner, you can cut out the bottom of the housing, outside the filter element channel. More air, and the housing passes a quick visual inspection.

My 73 340 air cleaner has a flap on the back underside that opens to allow in more air.  Do you think thats enough to make up the difference for a single snorkel?  It looks like vacuum may cause it to close, but it otherwise stays open which is the way I plan on leaving it.

[Talkwrench]

Dave I love that idea of having the twin intakes with cold air.. I'd love to get my hands on one .. very rare around these parts though.. Not so sure I would cut holes in the bottom of the unit.. wouldn't the hot air go straight in ??

 S'pose would be the same with taller fitler. So you just use a tall filter and leave the gap between the lid and the body?

Thats the sort of thing that I'll be doing with my '56 oil bath filter after covering it to paper, a complete other filter sits inside, lift the lid for a little more air..

[DoNotChallengeHer]

Gift from my baby brother.   ( the air cleaner )

[Talkwrench]

Road_runner any chance you could take a pic of that flap setup?   

Snokels have a few purposes [?]  A silencer, fresh air pick up, and ... to help create velocity. Thats all good ..but Its a shame that some choke the motor due to emmissions controls too, easy way for a factory to do it.. On our early Holden blue motors 6 cyl taking off the aircleaner will give you 7hp straight up.

[Road_Runner]

Road_runner any chance you could take a pic of that flap setup?   

Snokels have a few purposes [?]  A silencer, fresh air pick up, and ... to help create velocity. Thats all good ..but Its a shame that some choke the motor due to emmissions controls too, easy way for a factory to do it.. On our early Holden blue motors 6 cyl taking off the aircleaner will give you 7hp straight up.

I just happen to have pictures of my aircleaner from when I bought it on my laptop.  Here goes:

[Roppa440]

I have a formula for you to calculate the size of K&N filter you need for your engine which might help as long as the housing can flow enough.

First if all you need to know how much airflow your engine needs.

CFM required = CID x Maximum RPM / 3456

This assumes 100% volumetric efficiency at high rpms and also tells you what the minimum size carb should be on your engine.

Now for the filter.

To find circumference of a circle multiply diameter by 3.1416
To find diameter of a circle multiply circumference by .31831


CFM Formulas for Filters

Round: Diameter x Height x 6 x 3.14
Flat Panel: Length x Width x 6
Universal Round Taper: (Base + Top) / 2 = A
Take A x Length x 6 x 3.14
Universal Round Straight: Diameter x Length x 6 x 3.14

Square inches of filter required for an engine = CID x Maximum RPM / 20839

I have used this formula on a few K&N filters where they advertise the flow rate.

I have found their advertised flow rates to be + or - 10% from the calculated rates as stated above.

Basically their filters flow on average 6cfm per square inch of filter material. However design differences make some filters flow better than others.

[Talkwrench]

I have often thought about that idea of a flap that opens up a the flow rate rises and now Ive seen it , great struff, great idea.. MOPAR ! 

[Talkwrench]

Thanks Roppa.. good info