13 replies to this topic

[Daniel Watkin]

Hello,

 

I'm planning to swap out my air filter from the large bulky Rover unit (CAM6037) to a K&N Conical filter. I do not like the current filter as it makes the engine bay look crowded and it makes things hard to work on. The car is otherwise running very well.

 

I have a HIF38 carb and 1275 engine. As I understand, it's not a simple case of just swapping the unit over and job done? The carb will need a retune to accommodate the extra  airflow? I'm also unsure whether a new needle will be required, and if so, where is a good starting point? 

 

What else am I missing? So far I'm looking at

• Mixture adjust
• Needle replacement 

Is there anything else I need to consider?

 

Many thanks

Dan

[nicklouse]

Don’t bother. You will lose performance over looks.

 

a KN element in the standard hosing is the best performance option for your build.

 

but whatever you do you will need it set up correctly.

[andyapanel]

+1 for Nicklouse's comment.

 

if you read up on it, you will find drilling a few 3/4" inch holes in the base will help, too.

Read what Keith Calver has published.

You will also be less likely to suffer carb icing.

Good luck.

[sonscar]

How often do you need to work on the engine to make the filter a pain?Steve..

[alpder]

+1 Keith Calver's article about air filters and drilling the box. And an eye-opening comparison between airbox and cone. Plus, a cone will give you a shedload more intake noise than a drilled standard box with K&N filter in it. I've tried both - the noise difference is massive.

 

FWIW, when I had my car set up on a rolling road, they first tuned it without any filter (for ease of access). Then they fitted the filter (K&N in a standard but drilled airbox) to fine-tune. It made minimal difference to the mixture. We never tried it with a paper filter, though.

 

Also, if you're heading to a rolling road, first ask what needles they've got for your HIF38. Fewer people rock up for a tune with a HIF38 than with a HIF44. Stands to reason... people bolt on a HIF44 in expectation of getting more horses. (Again, Calver offers thoughts on this.) So I found the dyno people had shedloads of HIF44 needles. But not nearly as big a selection for my HIF38.

 

by the way, the older style box (TAM something, I think?) which I have will fit onto a HIF38 and goes on/off using just the one rear wing-bolt. (The front wing-bolt replaced with a permanent bolt which holds the lid/filter/case permanently together.) I shortened the stud in the elbow, and now the complete airbox can be fitted or taken out while assembled, using the one wing-nut. Can't really ask for easier access than that. I chopped off the intake pipe flush to the box, and drilled the front of it per Calver. OK, so I maybe lose a horse because I'm sucking warm air instead of cold... but I'm happy with the compromise between complexity/bulk and function.

Edited by alpder, 20 May 2024 - 01:15 PM.

[Daniel Watkin]

Thank you everyone for your responses! I'd not seen the Keith Calver article, but I've looked it up now, and the standard airbox does indeed seem to offer the most performance, very surprising!  In that case I'll stick with what I've got for now. 

 

Many thanks everyone!

[nicklouse]

Thank you everyone for your responses! I'd not seen the Keith Calver article, but I've looked it up now, and the standard airbox does indeed seem to offer the most performance, very surprising!  In that case I'll stick with what I've got for now. 

 

Many thanks everyone!

Daniel, there has been much speculation as the the reason and I think the Elbow before the filter housing has much to do with this.

 

without it the steel plate of the pancake filters acts a a reflector and a speaker. One it is way louder than you would think. And secondly the engine sound is reflected straight back into the engine. 
 

this could have fun with the airflow. The original performance Metro filter housing was a horizontal panel filter that also utilised an elbow.

 

it is really a strange thing that no one has really understood or explained.

[KTS]

 

Thank you everyone for your responses! I'd not seen the Keith Calver article, but I've looked it up now, and the standard airbox does indeed seem to offer the most performance, very surprising!  In that case I'll stick with what I've got for now. 

 

Many thanks everyone!

Daniel, there has been much speculation as the the reason and I think the Elbow before the filter housing has much to do with this.

 

without it the steel plate of the pancake filters acts a a reflector and a speaker. One it is way louder than you would think. And secondly the engine sound is reflected straight back into the engine. 
 

this could have fun with the airflow. The original performance Metro filter housing was a horizontal panel filter that also utilised an elbow.

 

it is really a strange thing that no one has really understood or explained.

 

 

i'd have thought that the sharp edge at the mouth of the carb from the backplate would create turbulence which would disrupt the airflow and potentially be the source of some of the noise.  the elbow the standard filter uses would certainly address that particular issue

 

having fitted a stub stack to mine it's certainly not as noisy as i remember it was without it

[lippo]

 FWIW, I'm going the other way - I've just removed my K&N cone filter and am putting the CAM6037 air filter housing back on. It's not even worth me buying a replacement K&N for the mileage I'll do, I've bought a standard air filter for the job. Just need to get it to fit now.

Edited by lippo, 26 May 2024 - 05:52 PM.

[Zaki]

Hi guys,

 

I don't want to start another topic as mine is similar. 

 

I currently have a regular K&N cone filter, but I find it a bit too loud when doing long trips. 

I've started thinking about swapping it for a CAM6037 box or maybe a custom one that HMW manufactures - https://www.hawthorn...-air-filter-box

 

Oh, and there's this other box made by Cooper as well (rare, but can still be found).

 

I'm looking for comfort here, not power. What do you think that I should pick?

 

My setup – 1988 Metro engine, HIF44

 

 

 

[Rubbershorts]

That looks tidy. I'd be interested in any forum users reviews also. Daz.

[croc7]

 

Hi guys,

 

I don't want to start another topic as mine is similar. 

 

I currently have a regular K&N cone filter, but I find it a bit too loud when doing long trips. 

I've started thinking about swapping it for a CAM6037 box or maybe a custom one that HMW manufactures - https://www.hawthorn...-air-filter-box

 

Oh, and there's this other box made by Cooper as well (rare, but can still be found).

 

I'm looking for comfort here, not power. What do you think that I should pick?

 

My setup – 1988 Metro engine, HIF44

 

 

 

Hi guys,

 

I don't want to start another topic as mine is similar. 

 

I currently have a regular K&N cone filter, but I find it a bit too loud when doing long trips. 

I've started thinking about swapping it for a CAM6037 box or maybe a custom one that HMW manufactures - https://www.hawthorn...-air-filter-box

 

Oh, and there's this other box made by Cooper as well (rare, but can still be found).

 

I'm looking for comfort here, not power. What do you think that I should pick?

 

My setup – 1988 Metro engine, HIF44

 

To misquote Calver; 'Tuning should be a compromise between expense and what is gained'!  That air filter housing is very nice looking but I modified my housing by adding a second snorkel and then drilling the 3/4" holes per KC's testing. Very happy with the result and was able to redirect money saved towards a good exhaust system and cylinder head. The engine is basically an air pump and increased air into the intake has to be able to flow through with minimal restriction.

Edited by croc7, 12 September 2025 - 10:00 PM.

[stuart bowes]

I know that's a bit of an oversimplification and clearly there's more to it (you're not trying to explain it all in one sentence obviously)

 

but is it really as simple as that, if minimal restriction was best then just a sock type filter or the pancakes or cones would be better, no?   ignoring the issue with noise.. 

 

is it not the case that by setting up a *certain amount* of restriction you can improve torque, or throttle response at certain rev ranges, and so on

 

geniune question, not trying to be a smartarse or whatever

 

(at some point I will read the Calver article, I've heard it mentioned a bunch of times)

Edited by stuart bowes, 12 September 2025 - 03:54 PM.

[Rubbershorts]

I know that's a bit of an oversimplification and clearly there's more to it (you're not trying to explain it all in one sentence obviously)

but is it really as simple as that, if minimal restriction was best then just a sock type filter or the pancakes or cones would be better, no? ignoring the issue with noise..

is it not the case that by setting up a *certain amount* of restriction you can improve torque, or throttle response at certain rev ranges, and so on

geniune question, not trying to be a smartarse or whatever

(at some point I will read the Calver article, I've heard it mentioned a bunch of times)

My limited understanding is there's a certain amount of ram gained with the original airbox, with the additional holes drilled, so it acts like a scoop. That said, the one in the link looks like it would provide plenty if that's correct. Daz.

Edited by Rubbershorts, 13 September 2025 - 09:27 AM.