Results 1 to 10 of 10
  1. #1
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    839

    Air Filter and Cleaner Modifications

    If anyone was to tell me that huge gains were possible by changing to a low restriction air filter, I wouldn’t put much faith in it. Basically, if even a poor filter is large enough that the engine is getting all the air it wants, then there’s nothing to be gained. In my case though, my air filters appear to be small and restrictive, so going larger and with freer flowing filter media might just be a wise move.

    Below is an advertisement for the filters where it states they were used in original 427 Cobras. Really? But I bought the advertising… and the air cleaners.



    Below is a picture of my engine with two 8” Stelling and Helling air cleaners which only have an element 1.5” high.



    They come with two filters, a more porous black one and green one similar to what one would find in a Briggs & Stratton lawnmower engine. Late last year I decided to clean the green ones and install the black ones to try them out. I noticed that when accelerating as hard as I dared in second gear, it didn’t take as much application of throttle to achieve the same result as when I had the green filters installed.

    Below is a picture of a black one as removed… with the further restrictive inner and outer perforated steel bands. The green one has been washed, but still looks dirty.



    Back to the K&N filters, I found a comparison of filter flow rate in the chart below:



    The Uni-Filter is probably the same as my green filters, although the same source does appear to indicate that the foam filters made by UK companies Pipercross and I.T.G. are better than the Uni-Flow. So K&N sounds like a good choice… if I can get them to fit.

    I’m not the first to want to install taller and freer flowing K&N air filters and it didn’t take much research to find a couple of recommended replacements. However I have a hood clearance issue. It’s not really the hood surface, but rather the reinforcing web that runs around the inside perimeter of the hood. The back air filter would have to be moved forward almost ¾” before any increase in height would be possible. This would of course mean the front one also has to be moved.

    I decided to make offset bases to move the air cleaners forward 7/8”. Any more, and there wouldn’t be enough room to fit the filters. As it was, I had to find an alternate to the recommended replacements as the latter were 1” thick. I managed to find ones only 5/8” thick. I even got them on sale…. Two for less than the regular price of one! This is important to me as I don’t like to spend too much money on an experiment.

    Below are the parts I made up. Two everything had to be made. Top left shows the new aluminum base made up from 1/8” plate. It didn’t come out too bad considering I made them with a jigsaw, file and some emery paper. I also made them a bit large so I could trim them better later, plus I wasn’t sure if I would need to provide some sort of lip to keep the filters lined up. A few pins along the inside perimeter of the filter might be an idea.



    On the right, is the original air cleaner base shown upside down. You can see how it raises the base up to clear various parts of the carburetors. At least 5/16” is needed. Rather than spend time trying to make rings, I simply used some 3/16” fuel line as seen on the left. I joined them using barbed couplers I salvaged from an old Keurig coffee machine.

    I also had to make offset rods. I made them out of plated threaded rod but have a piece of SS for later. Good thing as some of the plating burned off. Amazingly the first one came out with exactly the correct offset. The second one was a failure, but my third attempt came out successfully.

    Today I finished the installation. You can see in the picture below they are much larger. Just scroll back up and take a second look at the normal installation for comparison.



    All that’s left is to go test them. If a noticeable improvement is made, then I can see about making things aesthetically better as well as structurally sounder. It rained most of today. Tomorrow calls for more rain. And rain on and off for a few days after that. Wet roads don’t appeal to me as a test track. I’ll report back once I get the testing done.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  2. #2
    Join Date
    Jan 2002
    Location
    Marlow
    Age
    68
    Posts
    1,797
    Hi John, Thanks for sharing, I'm sure that any work you do on making the induction flow better will benefit engine power. Whether you can feel any difference with a road test is open to debate.. Modifying your carb butterfly spindles, can also gain but most will be found from a cold air feed to the carbs.

    Got about 10 bhp on mine with the above, as shown on the dyno, cant tell the difference on the road. So I only put my cold air feed in place on track days and drag racing!!

    Cheers Clive
    On On

  3. #3
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    1,042
    Nice upgrade . Getting more air flow in should improve thinks but you need to know the AFR ( Air Fuel Ratio) and see if your running leaner . Spark plug colour is a good indicator but only over all mixture. Clean the plugs and see what the colour are when you get back . The AFR is monitored through the rev range on a dyno or if you have a Lambda monitor fitted to see if your close to the ideal of 14.7:1 . Then you can look at jet sizes. When I took mine on the rolling road . We did a run with and without the airfilter to see how good a filter I had on . I ended up with fitting a Holley Powershot 3" just fitting under the bonnet oil like K&N . What made the most power increase was timing advance .

  4. #4
    Join Date
    Jan 2002
    Location
    Reading, Berks, UK.
    Posts
    1,586
    Not sure if any of you have ever seen the Roadkill series, HotRod Garage or this one, Engine Masters but here is some real dyno testing on air filters.
    If you haven’t seen any of the Engine Masters vids on Youtube before Motor Trend made it subscription then have a look.
    The lads on Engine masters do away with all of the hype and test for real, you might find it interesting.

    https://www.dailymotion.com/video/x693421

    For some reason I can’t find this actual one on Youtube but this is it on another site.
    Check out some of the other testing, a lot of myths and “ I heard this” really put to test

    Cheers

  5. #5
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    839
    Quote Originally Posted by clive a brown View Post
    Whether you can feel any difference with a road test is open to debate.. Cheers Clive
    I too have my doubts other than I do feel a difference between the green and black foam filters. In the rpm range I normally enjoy, having the freest flowing filter available might not be noticeable.

    Quote Originally Posted by jon1d View Post
    Nice upgrade . Getting more air flow in should improve thinks but you need to know the AFR ( Air Fuel Ratio) and see if your running leaner. What made the most power increase was timing advance .
    I am somewhat concerned that I might run leaner, although the carbs were set up by a company that had no idea I would install such small filters, i.e. a choking action. So the hope is I'm already running too rich. On the other hand, the sparkplugs always looked good, so if it is indeed fine now, it may run lean with the new filters. I have heard that the main jets can require as much as 4 changes when switching from no air filter to a "normal" one.

    As far as the timing goes, I spent quite a while a few years back working on that and am optimized as best as possible without dyno testing... er... as far as I can tell. Hard to hear pinging with side-pipes.

    Quote Originally Posted by Bigblock View Post
    The lads on Engine masters do away with all of the hype and test for real, you might find it interesting.

    Cheers
    Hype... tis a grand thing, isn't it? LOL. Very interesting video. Thank-you for the link. I must check out some others. Odd that little 6" filter did as well as it did. Maybe my twin 8" ones aren't that bad, but I still think the perforated metal around the inside and outside of the foam can't be good.

    Darn... I really want to try this.... but it's absolutely pouring out right now. I was going to tease you that it would soon blow away eastward and you'd see it in a day or so, but without body language, a little teasing can sometimes be taken wrong.

    Thank-you all for your replies.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  6. #6
    Join Date
    Jan 2012
    Location
    Perth
    Age
    53
    Posts
    1,681
    Hi John,

    Interesting stuff, we will be running the single large Cobra style filter (dual quads as well) so clearance could well be an issue too.

    cheers
    Kiel and Duncan (dad and the lad errr young man now)

    AHP Crendon Chassis No 1
    Ford FE 434, dual quad, Toploader total old school all the way
    https://www.crendonreplicas.com/
    http://www.absolutehorsepower.co.uk/

  7. #7
    Join Date
    Feb 2003
    Location
    Devon
    Age
    53
    Posts
    7,767
    Ran my stroked sideoiler with a Stellings housing and a K and N filter.
    No issues at all. The filter can be washed and used over and over.

    Kiel, you should be fine with a pair of Stellings with K and N filters mate.
    Might look better than the ugly oval thing......
    2003 Dave Brookes Dax 350ci Chevy SB.
    2008 Crendon 462ci Ford Sideoiler No.43
    2012 Crendon 351ci Ford Cleveland No.24
    2019 Crendon 445ci Ford FE No.66

  8. #8
    Join Date
    Jan 2008
    Location
    Basingstoke
    Posts
    1,109
    Interesting stuff... I really struggled to get any air cleaner under the hood after an engine swap, let alone anything that would flow properly. I saw the clip of the test that showed that top down air flow worked the best, so I made my own housing - based on a baking tray....

    Attached Images Attached Images

  9. #9
    Join Date
    Jan 2012
    Location
    Perth
    Age
    53
    Posts
    1,681
    Quote Originally Posted by Neil O View Post
    Ran my stroked sideoiler with a Stellings housing and a K and N filter.
    No issues at all. The filter can be washed and used over and over.

    Kiel, you should be fine with a pair of Stellings with K and N filters mate.
    Might look better than the ugly oval thing......
    Oh you've hurt my feelings they match my valve covers so well too
    Kiel and Duncan (dad and the lad errr young man now)

    AHP Crendon Chassis No 1
    Ford FE 434, dual quad, Toploader total old school all the way
    https://www.crendonreplicas.com/
    http://www.absolutehorsepower.co.uk/

  10. #10
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    839
    Nice looking job there AlexB74. Made me think of the salad bowl effort shown in the link BigBlock posted, but yours is more esthetically pleasing as well as being low profile.

    Neil O: I learned something from you today. I didn't really know the difference between and oval and an ellipse. Now I do. Thank-you.

    Now... the results:

    I finally got to test my car today. Although the rain had stopped, the roads didn’t really dry out until this afternoon, however it was cold out (low 50s... 12 degC) so traction still wasn’t optimal and I didn’t dare try to push it too hard.

    I didn’t expect much as I thought most of the benefits of the new air filters would be higher up in the rpm band. This may be true, but I was surprised at the improvement in the lower rpm range.

    First of all, the engine was way more responsive. Instant acceleration. I had a very tiny hesitation before and I had been thinking of experimenting with pump cams, but it’s completely gone now. The engine starts pulling very strong at 2200 rpm where before it was about 2500 rpm. I thought it worked well before, but now it’s incredible.

    Thinking about this, I think the reason it’s so much better is that the old restrictive elements acted as a choke and the engine was running too rich.

    I am very satisfied and will now put some thought into making nice offset bases that have a lip to help center the filter. I can use my original bases with the spacer section removed and a new carb hole cut 7/8” off center and then rivet on a new base made from a cheap 14” base cut down to fit, centered on the offset and egg shaped to cover part of the original hole in the old base.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •