Well I have been curious about all this as I noticed Ford had two air cleaner sizes one for the 144-250 and a larger one for v8. Can't remember the exact diameters right now. Is there more sizes for passenger cars? The 144 was the first small six but the air cleaner for that is the same diameter as for my 250? Been thinking that since these engines have been described as air pumps maybe my 250 needs the v8 diameter element or comparable element square inches. I tried to test fit a v8 air cleaner from a 351 Tbird on my 250 Bronco and the oil fill on the valve cover interfered with it. So then I looked at some carb hats and remote air cleaner but not sure if all this is worth the time for a stock 250 maybe overthinking it. Other 250 owners considering this?
All Small Six air cleaner sizes, carb hats all that stuff
- Thread starter bmbm40
- Start date
This relates to all small sixes
In my search for a stock air cleaner that would fit the stock 250 RBS and still let me use my stock 66 Mustang hood I acquired several air cleaners. One, from an early 80's 200, is 13-1/4" in diameter and would use a 10-1/4" OD filter. It doesn't fit the carb.
The one that fits perfectly is from an early 70's Mustang/Maverick 250 six. It has a diameter of 14-1/2" and uses a filter with an OD of about 11-1/2"
I found both of these on eBay.
I seem to recall that the V8 air cleaners were 14", which would be about the same size as the one for the 250.
Both of these have drop bases so they sit low on the carbs. I think this is because the I6 carbs sit higher than the V8 carbs do so the drop base helps with hood clearance. I also found that there are different stampings for the different carbs. So, for example, the 200 air cleaner does not fit the RBS carb because the stamped humps in the base are in the wrong places and aren't deep enough.
The one that fits perfectly is from an early 70's Mustang/Maverick 250 six. It has a diameter of 14-1/2" and uses a filter with an OD of about 11-1/2"
I found both of these on eBay.
I seem to recall that the V8 air cleaners were 14", which would be about the same size as the one for the 250.
Both of these have drop bases so they sit low on the carbs. I think this is because the I6 carbs sit higher than the V8 carbs do so the drop base helps with hood clearance. I also found that there are different stampings for the different carbs. So, for example, the 200 air cleaner does not fit the RBS carb because the stamped humps in the base are in the wrong places and aren't deep enough.
Last edited:
Thanks for the detailed info and pictures as that is very helpful. I believe I currently have the same early 70's model that you have and it has the 11.5 " filter and it just clears the oil filler cap. And for a 289 I found the stock was a 14" filter at NAPAand the 170/200 were listed at 12" probably 11.5 actual. The 14" housing I know will not clear the oil filler cap so If I had to have more square inches of filter area I could do a carb hat and a remote filter box like newer vehicles. Maybe more work than is practical but with a remote airbox in a good location I could hopefully draw in cooler air mostly. And that stamped hump is a factor I forgot about.
The Maverick AC's probably have most clearance / least rise as mentioned.
Another option - the bottom is thin steel and can be formed to fit most carb setups fairly simply.
Heres an RBS type Mav' AC with bottom simply hammered flat and hole cut to fit Holley/Weber 32/36. Almost any carb can be accomodated.
. 
. 
. 
Another option - the bottom is thin steel and can be formed to fit most carb setups fairly simply.
Heres an RBS type Mav' AC with bottom simply hammered flat and hole cut to fit Holley/Weber 32/36. Almost any carb can be accomodated.
. . . OK, yes, thank you John Ha and powerband. That is exactly what my air cleaner looks like and mine is missing the snorkel. Good to know I can adjust with a hammer on the bottom for various carburetors because I do plan to change my carburetor also which caused me to start thinking about the whole carb/ac thing. I have been getting interested in the small base 278 cfm 2v Rochester carb as it is not a tall carb and can be fit to the existing carb base much like the Carter BBD. Xctasy was kind enough to mention this carb in another discussion about carbs. Here is an informative link:
One thing I've noticed with this air cleaner is that it has the opening for the snorkel on what I consider to be the warmer side of the engine above the exhaust and that is something I would like to change. Also I still can't help but think that a larger air cleaner might be better. A 289 (with a 14" air filter) is only about 15% more displacement than my 250 (12" air filter) and this current request for advice is all in anticipation of a warmed over 250 with better breathing capability due to a larger carb, cam, head/valve work and long tube headers at some point.
Thank you
One thing I've noticed with this air cleaner is that it has the opening for the snorkel on what I consider to be the warmer side of the engine above the exhaust and that is something I would like to change. Also I still can't help but think that a larger air cleaner might be better. A 289 (with a 14" air filter) is only about 15% more displacement than my 250 (12" air filter) and this current request for advice is all in anticipation of a warmed over 250 with better breathing capability due to a larger carb, cam, head/valve work and long tube headers at some point.
Thank you
I don't think "an early 70s" would have that black vac switch seen in post #2. The 1 in #5 looks like the late Mav 250 'drop base". Speculation, not fact. Love some solid evidence. #4 would B interesting for positive ID too.
True! I got both #2 and #4 from eBay and they were listed as Mustang/Maverick air filters. #4 came with a lid that had 71 Mustang written in paint pen. #2 didn't come with anything to identify it but I suspect it was on a mid to late 70's car. As far as form and fit it's the same thing as #4 - just with more sensor holes.
Thanks for the compliment. It wasn't hard at all although there were a few issues that took some creative thought and a few iterations to resolve. It's basically stock - rebuilt by a local shop.
I'm very happy with it, other than struggling through some carb issues at the present. I didn't do a build thread here but did update my web site which, unfortunately, no longer exists.
John Ha, I see from the pics your 250 is in a convertible, nice! And you kept the diagonal stiffener bars with your Monte Carlo bar. Is the exhaust just a conventional single 2" system? When you picked a carb, did you look at an 1101, or is the RBS shorter? I wanted to leave a little additional air cleaner information for the benefit of future searchers. If you do have an 1101 carb, 1100 air cleaners aren't likely to fit. I had a hard time trying to find one that worked. The 1101 choke is mounted way higher on the carb body, and the air cleaner needs a big "dent" in the bottom to clear it. Kind of like the pics of air cleaners seen earlier in this thread. I eventually got something worked out, but I wonder if an RBS air cleaner would've fit.
Thanks. The Monte Carlo bar is actually a custom fab. Neither the curved one nor the straight one cleared the air cleaner so I cut up the curved one, did some extra bending and welded it back together, adding the center straight piece from an old, dead bicycle I had in the garage attic.
The exhaust is a 2-1/4" pipe from the transmission crossmember on back. It's one of the two that was in there from the 351 I removed to put the six in. The head pipe is a pre-fab 2" unit for a 69 Mustang that I bought from one of the Mustang parts houses and modified to mostly work with my car. Haven't got it totally right yet because there's still a buzz underneath at times.
I didn't look at carbs at all. The engine came with an RBS so I stuck with it. I rebuilt it, apparently poorly, because it's a gas hog. I've since altered another RBS that I bought from a member here so it works with my throttle linkage - I just welded a piece of steel onto the carb throttle linkage. That one seems to be giving me much better fuel economy.
The air cleaner was one of the more frustrating and time consuming hurdles for me. I bought 4 different ones from eBay over the course of a year or so, not knowing what exactly would fit. One was the offset model from an early Bronco, one from a late 60's 200 Mustang, one from a 71 Mustang and one from a 70's Maverick. The latter two both fit but someone had drilled a bunch of holes around the bottom of the 71 Mustang unit so I didn't want to use that. I gave those away to members here, since I couldn't use them, no one wanted to buy them and I was tired of storing them.
You can find the RBS air cleaners on eBay from time to time. They tend to be kind of expensive but if they fit your car and you want an original look it's worthwhile to spend the money. Pretty much any Ford product from 70 through 74-ish with a 250 six uses that carb, at least from what I've seen.
I have a big log/big valve head I'm going to put on my car one of these days. I picked up an 1101 carb for it, and made an adapter out of an old aluminum spacer to put it on my original head with the 1.5" carb opening, just to check the carb out. Of course the air cleaner I had on the old 1100 carb didn't fit on the 1101. I didn't like the uncertainty of ebay buys, so I went to an old farmer with a bunch of old Fords out in his grove, and found a rusty '64 Galaxy air cleaner made to fit the high choke on an 1101. It was a big ol' toploader design that wound up just barely interfering with an under hood stiffening rib. So I cut it down into an open element minimalist design that fit fine then. And I like your homemade Monte Carlo bar. I thought it looked a little unique. I made my own too, with a front and a back bar that don't require any new holes to be drilled. I like how you used bicycle parts for yours. My first iteration of my front bar used a section of tubing from my sister's old swing set. Whatever works!
