K & N Filters, which needles to use?

DamianZ28

Active Member
Have bought pair of K & N Air filters for my V8, seems I will need to update the needles in the HIF6 SU's, Moss recomend the 'BAF' size for the upgrade, anyone else tried this ?

Also have a brand new Mallory alloy performance electronic Disty with the corrosponding coil & ballast resisitor to fit, so combined with the newly finished top end rebuild, should be a little quicker 8)
 
Hello Damian,

Are you fitting the filters inside the existing air box or onto the end of each elbow with the box removed or onto the end of each carburettor?

Does your engine run with the original small valve P6B heads or the latter large valve heads?

The BAF needles are quite a bit richer compared to the original BBG or BBV needles that were fitted into the HIF6 carburettors originally, just as the K & N filters will breathe a lot better than the original paper filters. Trial and see. If they prove to be too rich, go back one to BAK. Do lets know how they go and what you find.

Ron.
 
Hi Ron,
would like to use your expertise
I am also playing with my V8 bog standard
I fitted 2 K&N filters to the end of each carburettor and found out that mix was too lean, despite adjusting mix screw ( up to 2 complete turns)
I found out my HIF6 are equipped with BBV needles
Hence should I start with BAK profile and then a furhter upgrade to BAF if needed ?
Going to place my order to Moss asap.
Many thanks in advance for your advice
Paolo
 
Hello Paolo,

I'll do my best to help out where I can.. :)

The mixture adjustment screws on each HIF6 carburettor are only there to set the idle mixture. The taper of the needle determines the mixture for all points off idle. So essentially whether you are using your original BBV needles or the richer BAK or BAF needles, the idle mixture setting for all three will be very close if not identical. Any adjustment required will only be slight..in fractions of turns.

With the filters fitted, use the lift pins on each carburettor to check the idle mixture. When the pin is lifted, should the idle speed rise slightly then drop back essentially to where it was originally, then the mixture setting is pretty well where it needs to be. Should the engine revs drop right down or stall then the mixture is too lean and the mixture screw should be turned in slightly and test again until correct. If the idle speed increases and does not drop back then the idle mixture is too rich and the screw should be turned out slightly,..then test again. Each carburettor should be done and the settings on each should be as close to identical as possible.

To test off idle, drive the car and accelerate uniformly in top gear and feel for engine hesitation. If this occurs then the mixture is too lean at the speed and revs at which it revealed itself in which case a richer needle will need fitting. Of course all this is a compromise with standard needles. The ideal way is to run the car on a rolling road and have the needles polished to suit. In this way you have a custom needles specifically for your car.

How much ignition timing is your engine running at idle Paolo?

Ron.
 
I went from BBG to BBW when I fitted K&N's and later Range Rover heads - on the advice from Gower & Lee. Then I decided they were just tad too rich.

I'm now on BAF but not convinced they're exactly right...I think they might be a touch lean just coming off idle.

100_1876.jpg


Guess I really need a rolling road.... :roll: ££££££££££££££££££££££££££
 
Hi Ron,

Car has the standard P6B heads with new Valve springs, Rocker Arms/shafts & decoked. Fitted the K & N's last nite directly on to the SU's, leaving the elbows off & touch wood it runs really nice, took it for good run to get hot, no flat spots or hesitation, smooth tick over, I have set the mixture screws as per the standard workshop manual, level with bottom of each piston & then back 2.5 turns, seem to work so far!

Thanks fo ryiur advice :D Cheers Damian
 
glad to hear that Damian got it sorted.... :!:
Mine is not satisfying
Now I know I was only enriching the idle mixture, that's why I got no improvement ( such a empty head...)
well, my V8 is running with timing set at -2
using shell v power 99 octanes + castrol lead replacement with octan booster.
no pinking,great intake sound from filters, good pull at low revs ( approx up to 2000 rpm) but engine pull flattens at 3500+ rpm and have hesitations to go higher like it was too much air in mixture.
All electrics have been checked and working perfectly with standard set up.
So, should I try the richer needles ?
Thanks in advance
 
48401403c said:
no pinking,great intake sound from filters, good pull at low revs ( approx up to 2000 rpm) but engine pull flattens at 3500+ rpm and have hesitations to go higher like it was too much air in mixture.
All electrics have been checked and working perfectly with standard set up.
So, should I try the richer needles ?

When you get the problem at 3500+rpm try pulling the choke out a little, that will richen the mixture and if it cures the problem then it's fuel related, so could be the needles, if not, look elsewhere.
 
Hello Paolo,

If all else is ok, then with the filters drawing more air you will almost certainly require richer needles. Harvey's advice on pulling out the choke will certainly show if it is the needles. Checking one or two spark plugs will also be a definitive pointer. If you wish to check, once the engine reaches 3500 rpm or so and starts to hesitate, very quickly pull up and shut it down,..don't let it idle,..engine off as quickly as possible. The appearance of a spark plug is a picture of the engine's air/fuel mixture, it's health if you like, at the time it was shut down. If you see insulators and earth straps that are stark white,..then that is a lean mixture indeed. Lean mixtures burn hotter than rich mixures, so don''t run at those engine speeds any more than is necessary as expensive engine damage can result. If you see tiny metallic specs on the ceramic of the insulator, then the damage has already happened. It sounds scary I know, but it is better to be forewarned than let it become too late.

Ron.
 
Harvey, Ron,
many thanks for the advices ( even if the latter being a little bit scarey, yes.... :roll: )
Going to check this weekend ( all I need is an empty road ....)
 
Hi Damian,

Trying to see if you went for a new set of needles, if not which ones do you have now that you're happy with the running? I also have K&N-type filters, but within the air cleaner box, Magnecor leads, an Ignitor dizzy module and a Flame Thrower coil. I'm looking for new needles that'll suit my application better, as I'm not quite happy with the running. The carbs are not right so I'm getting service kits for them to sort them out as well as I can.
 
mine is 99% a problem of needles :)
This long weekend, despite rain I was able to check the trick suggested by harveyP6.
Pulling the choke did the difference, not perfect but definitevely better.
I used 8 new spark plugs and off I went, found suitable road and pulled "the magic"
Unfortunately I can drive the P6 only on weekends or during night ( funny pollution rules apply in Milan ) but I will try to put some miles under the belt with enriched mixture via the choke and will check plugs conditions in a while.
But I am looking forward to order my BAK very soon.
thks to you all for suggestions
Paolo
 
I just read this topic and maybe I can add some ideas. I have a 1984 Landrover 90 V8. The enginebase is 3.5 Rangerover, the heads are P6 with 10,5:1 compressionratio and it is equipped with twin HIF44. The exhaustsystem is pretty standard (Bosal). The HIF's had BBG needles with the yellow springs AUC1167. I replaced the standard airfilter with K&N directly to the carburetors and found out it ran too lean.
After some expirements, the combination that did the trick was BBW needles combined with the yellow spring AUD4398 (the big ones for the ballbearing pistons). I tuned the CO at idle on 4,5% CO. This old Landy now idels perfectly, accelerates without flat spots from 1000rpm in about 14 seconds from 0 to 60 mph and reaches a topspeed of well over 100 mph in fourth gear with a beautiful exhaustnote. It reponds well to the throttle and is very flexible. No problem using only third gear in town. One other detail: I use ATF Dextron 2 as damperoil.
 

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Hi can anyone tell me the difference between BGC, BBV, and BBG needles regards which run richer and where in the throttle range, cheers George
 
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