Air Filters

[zblu]

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]

[ 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]

/ubbthreads/images/graemlins/iagree.gif ZBLU, Just about any filter will exceed the performance of the originals.--Fwiw---Keoke

 

[zblu]

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]

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

 

[zblu]

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]

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

 

[zblu]

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]

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]

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]

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]

[ 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

 

[Rick60]

Tony and Dave, just found a site offering airfilters for the BJ8
https://www.speedograph-richfield.com/html/speedograph_air_filters.html
Has anyone had experience on installing these filters and on the performance alteration?

 

[zblu]

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?

 

[stever]

Hello, Guys,
I was able to make the Ramflo filters work with my BJ8, but I had to use a "blank" base plate and cut out the proper offset for the front carb. Seems to work fine. https://www.carburetion.com/RamfloFilters.asp
Stever