I've personally seen far too many Weber 45's spit back and set light to Foam style filters (Pipercross and other brands too) to ever risk using one. That said, I didn't ever use any filters on my hot Pinto - zap too much power - never had an issue nor have any of my pals using 40's 45's or 48's etc.
Stub stacks however make a big difference to power delivery and even the running of the engine. It's something alot of people underestimate IME.
Are there specific k&ns for connecting to carbs rather than normal intakes? All 65mm deep ones suitable and I just need to match up the relevant intake diameter?
Cheers
I believe so. The Capri boys would be the people to ask I reckon; they do after all mostly use 38DGxSs.
Whilst I agree with you in principle, I can only speak from my own years of experience - on my drag Capri, fitting a filter over the trumpets ate over 10bhp. Fitting short trumpets alone did the same. Fitting K&N filters with no trumpets was around 12bhp. This was all measured on the same dyno, the same day in constant temps etc so you cannot get more accurate. Our best results were using no filters at all with 63mm Trumpets. (75mm would've been better over 200bhp my dyno man said but we only had 187bhp)
When I say 'Drag' Capri, i mean it was doing 5000 miles a year on the road too Until the year we won the championship - that year it was strip only as on slicks.