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Air Filters

zblu

Jedi Knight
Offline
Am thinking of putting unifilters on place of the pancake type as they appear to be more efficient in airflow and dirt entrapment, anyone have any thoughts?, and/or any other makes?
 

Dave Russell

Yoda - R.I.P
Gold
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[ QUOTE ]
Am thinking of putting unifilters on place of the pancake type as they appear to be more efficient in airflow and dirt entrapment, anyone have any thoughts?, and/or any other makes?

[/ QUOTE ]
I guess you are referring To The H4 SU carbs on the BN1. Almost any filter would be better than the originals. Unifilter is ok.

I really prefer the K&N filters. You can see them here:
https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=32629&SortOrder=4

Or K&N #56-1390, here:
https://knfilters.com/search/product.aspx?Prod=56-1390

Or victoria British # 3-1803

Or you could adapt the K&N filter elements, K&N # E-3180, to your filter cans here:
https://mgaguru.com/mgtech/carbs/cb201.htm

Several possibilities,
D
 

Keoke

Great Pumpkin
Country flag
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/ubbthreads/images/graemlins/iagree.gif ZBLU, Just about any filter will exceed the performance of the originals.--Fwiw---Keoke
 
OP
Z

zblu

Jedi Knight
Offline
Well, have chosen the unifilters as they give a spec of 4 micron passing where k&n give a spiel, carbs are h6 actually, taking the cold air box off as I believe I will get better airflow this way, altho I do use a k&n on my webber dcoe 45 on my beach buggy
 

Dave Russell

Yoda - R.I.P
Gold
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I'm a little confused. In your first post "Am thinking of putting unifilters on place of the pancake type", you didn't mention the cold air box or H6 carbs. In any event;
Increased air density increases horsepower. Since underhood temps could easily be 100 degrees F. higher than outside air temps, and, air density increases about 1.8% for each 10 degree F. drop, the cold air box has the potential to increase intake air density & power by up to 18%. The box presents no actual restriction to air flow & a high flow filter can easily be fitted to the front side of the air intake hose. It's your choice.
D
 
OP
Z

zblu

Jedi Knight
Offline
Sorry I confused you there Dave, I understand the cold air concept, however after the air has found its way past the grill, down a long tube thru several bends into a smaller rectangular crosssectional then going thru a in line filter I believes that I'm going to try the foam filters and leave the tube to assist in supplying external air as well, just thinking 2.7lx5000rpm=13.5 m3, lot to hope for down a 100mm dia tube!
 

Dave Russell

Yoda - R.I.P
Gold
Offline
Hi zblu,

Since the engine only intakes half of it's displacement every revolution, at 5,000 rpm, I come up with 6.6 m3 per minute flow.

At the 100mm air hose I come up with 5.9 m/min. velocity.

At the intake of the 100mm by 50mm box, I show 8.9 m/min. velocity.

At the rear half of the box, the numbers are about 4.5m/min. velocity.

All these velocites are very low, like about 0.4 mph or so.

In our terminology, the pair of carb throats are about 4 square inches of area. The box is about 8 square inches area. The hose is about 12 square inches area. There is unlikely to be much restriction in the box & hose.
Regards,
D
 
OP
Z

zblu

Jedi Knight
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Thanks for all the info Dave Russell, so in essence the air box does do more than just look pretty, contrary to others opines!
 

ynotme2

Senior Member
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Dave,

Maybe you can shed some light on this piece. I have looked for K & N filters for my BJ8 with 2" SU's. But I never see them advertised. Do you know what model number to use? I have stock 2" SU's with no cold air box or anything like that. I looked at the moss catelogue that you posted above and didn't see anything for the 2" carbs. Any ideas?
 

Dave Russell

Yoda - R.I.P
Gold
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Hi Tony,
The BJ8 presents some clearance problems for filters. The front filter needs to be offset for shroud clearance. There is very little room between the carb & bonnet opening. It appears that the BJ8 is the only one with this special problem & few manufacturers want to bother with such a limited application. When I contacted K&N about this, they indicated that they would look into the feasability of making some, but no word a year later.

Possibilities:
K&N filters for 2" HD8 SU Made for Jag but not correctly offset to fit BJ8
https://www.filterpower.co.uk/kn_bolton/jaguar.htm
However,
Blank back plates that could possibly be made to fit BJ8 See above
https://www.filterpower.co.uk/blank.htm

Ramflo foam for HD8 May fit BJ8
https://www.carburetion.com/RamfloFilters.asp

Some possibility - Again don't know if they will fit BJ8
https://www.aptfast.com/

You could try adapting/fabricating filter covers to your existing filter housings. Would have to find a suitable K&N filter element to fit.
https://mgaguru.com/mgtech/carbs/cb201.htm

Overall, a bit of a problem selecting a filter that will fit the BJ8. You will just have to contact the sources for details. Good luck,
D
 

Keoke

Great Pumpkin
Country flag
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Hi Dave, I have tried most of the those items and nothing seems to allow installation on the front carb.I tried putting K & N filter material inside with the rest of the Pot Scrubbing material and it starved the engine for air at => 3000 RPM.---Keoke
 

Dave Russell

Yoda - R.I.P
Gold
Offline
[ QUOTE ]
so in essence the air box does do more than just look pretty, contrary to others opines!

[/ QUOTE ]
Since air density & power increase about 1.8% for each 10 degrees F. temperature drop & it's entirely possible that there could be 100 degrees F. temperature difference between underhood & outside temperatures. Any way you look at it, the air flowing through the radiator & over the carbs is likely to be 180 degrees F. or more. There is potential to gain 18% power. Jetting adjusted accordingly.

I also find that the carb bodies themselves run much cooler & reduce the fuel boiling/vaporization in the carbs quite a bit. Reduces or eliminates the need for a heat shield.

If you live in a dusty climate, I would suggest putting a good filter on the front end of the intake hose. On the BN1-BN2 it's easy to replace the top grill mounting nuts with wing nuts. This allows you to reach in through the fender wells, remove the nuts, & swing the top of the grill out for complete removal. It just plugs into the bottom. Easy to work on & service the air filter.
D
 
OP
Z

zblu

Jedi Knight
Offline
as an adjunct to previous, would installing a fan to run on for a few minutes like some cars today reduce the vapor lock probs on restart?
 
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