My present 914 has a flat-four, 2.0 liter engine, but it had been converted to a twin, dual-throat Weber 40-IDF by its prior owner. Throughout all of my 914 owning years I have heard the oft-repeated admonishment, "Leave the car FI'd: don't convert it to carbs" repeated by Those Who Know, since older 914s with original injected fuel systems tend to be problematic and in poor condition (due to wear, aging and lack of proper engine maintenance over the years) and tricky to keep the OEM FI operating properly.
There are, of course two equally valid opinions on this contention but since I no longer have a choice in the matter, I am now faced with gaining the necessary Weber carb knowledge and acumen to properly adjust and tune my car's 40mm IDFs. I even have the Haynes Weber and Weber/Dellorto carburetor tech books in my Porsche library. That said, they contain a hell of a lot of precise material and detailed information on proper carburetor adjustment (too much!) and it's all a bit overwhelming for someone like me, who has had to cope with 'undiagnosed ADD' since childhood. If you need some clarification on this last point, let me explain that ADD makes intense concentration and single-minded focus for sustained periods quite challenging! Ditto for anything requiring prolonged study, such as educational courses and programs (but I've made it this far, despite a lot of lost sleep and chronic mental fuzz throughout my degree programs and writing efforts).
So there it is. I suppose I'm asking anyone out there who is a carburetor whiz of the Weber/Dellorto kind to kindly share some opinions on what I should do to be assured my car's carbs are spot-on-the-mark, adjustment-wise. I am, as a VW owner past & present, already somewhat familiar with such beasts as the SOLEX 30PICT carb, but Webers and Dellortos are a whole new type of fish in my frying pan.
My car seems to have a mild and intermittent tendency to experience pops and slight backfiring after the car is warmed up and moving at close to speed (say on a highway, accelerating to about 70 or so). Given what little I know about carbs, this suggests to me that the carbs may be running a bit lean...that the idle and/or main fuel jets may be slightly too small, requiring a larger set of jets for a slightly richer fuel mixture. My car's plugs do not appear to have excessive carbon deposits on the tip, but I haven't yet pulled the idle and main fuel jets to note what size they are.
Given all of the above, and the fact that the car has recently had a valve adjust and 'supposed' tune-up at my local Porsche shop, I would welcome any shared insights on how best to go about further 'drilling down' into this minor but irritating anomaly, so as to make running operation smoother.
I'm sure some will say "If you aren't satisfied with how your carbs are presently adjusted, get your shop to take a look and make any required adjustments." Easily understood advice, but I thought that instruction was complied-with on my last visit (perhaps it was not adequately done). I wish I knew a good local shop that could do carb adjustments on Weber IDFs on the car, but I am a bit flummoxed in trying to find a shop anyone recommends for this purpose. Another small problem is that although we have several Porsche-specialist shops in town (who will work on 356s, with their similar carb set-ups), these shops deign to NOT work on 914s! The old '914 bastard child/almost a REAL Porsche but not quite' syndrome again, we 914 owners have always had to contend with, sadly.
Anyway, feel free to pitch any ideas this way, concerning the subject. I'd be grateful for any inputs by those with real knowledge and experience in coaxing Webers to perform properly (whether on 356s or on 914s! Thanks, folks!
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For inspiration, here's a picture of how I installed the wideband in the old Mercedes.
