Practically Classics Forum

Hi All
Am thinking about fitting a pair of K and n air filters to my 77 r/b mgb roadster. As far as i am aware the only mod so far is electonic ignition. The carbs at present are as standard. My question is about the su needles-do i need to change them and if so what needles do i need to deal with all the extra air.
I eventually intend to fit a stainless steel sports manifold .Just trying to pep the old thing up a bit without getting into camshafts and skimming and balancing bits .
Any thoughts please
Cheers John B

The answer is yes - go to Burlen Systems website - they are the foremost SU expert and stockist - e-mail or call them stating your cars exact spec and what you intend to do.
They will quote the correct needles and be able to supply from stock - simples

Thanks for that- Conacted Burlen systems and had a chat. The guy was unable to tell me and suggested i contact K and N for their recommendation or ordered a few sets and went on a rolling road to set it up!
Was hoping someone out there had done this before and i could simpy set the carbs up with new needles as they had done.
Any other ideas ?

John B

I would definitely stand to be corrected on this one as although I have extensive knowledge of specialist tuning it was on Audi’s and VW’s and not old cars and certainly not SU’s – but I struggle to imagine K&N’s making much difference to jetting – they never made any difference to cars when I did rolling road tuning – and that includes power gains. In my experience a K&N would give 1 maybe 2 HP gain when newly cleaned and oiled, this would diminish to no gain as they became soiled. As a point of interest when we prepared the Audi UK rally cars we used standard paper elements.

I would say a rolling road is the sensible option because at the moment you are assuming the carbs are jetted correctly – this may not be so and changing them may put the tuning further out spec.

If it was mine, well to honest I wouldn’t be fitting K&N’s but if I did I would stick them on and see how it ran and go from there.

I once fitted a K&N to a mini and also fitted the jet that was recommended. i must its was a right old pig to drive, massive flat spot terrible running fitting the old needle didn't cure it, i fitted the old filter assembly back on and it was perfect again even with the new needle fitted back on.

Thanks for all the comments guys -gonna go away and ponder before I commit any hard earned. Cheers John

Looks like, from the consesus, that K&N's are a cosmetic gain akin to go faster stripes then
Speaking personally, I have always thought that a properly set up engine i.e. ignition, mixture and tappets and maybe polished and ported will be more than adequate compared to some "tuning" and putting a car on a RR aint cheap.
That's all my B roadster has ever had and it goes like a rocket (Well if I'm honest, a rocket that sounds a bit like a sewing machine)
PS. The previous owner had my Princess on a RR after set up and it only managed 85 BHP at the wheels - quite disapointing really as it's brochure BHP is 105 - I guess the Auto box saps some power but my point is, unless you intend to go racing, why bother going to such expense

Agree with above.

IMHO if you were to do some heavy tuning on the engine, including major porting, large bore manifolds and exhaust, larger carbs etc. then the amount of air the engine will need to suck in particularly at high revs might warrant a K&N style filter. However on a standard engine it's going to make virtually no difference, so if I were you I'd fit standard needles.

Cheers

Wicksy wrote:PS. The previous owner had my Princess on a RR after set up and it only managed 85 BHP at the wheels - quite disapointing really as it's brochure BHP is 105 - I guess the Auto box saps some power but my point is, unless you intend to go racing, why bother going to such expense

That doesn't sound unreasonable to me. I would think an auto 'box could easily absorb 20 bhp, even a manual 'box can absorb 15.

BEWARE OF ROLLING ROADS, I speak from experience!



John Simpson.