Intake Manifolds

There are a number of carb and manifold choices. The most popular are the factory Fiat waffle manifold seen in this article. There are also two others. The PBS manifold, and the Alquati. Both the Alquati and the PBS manifolds are cast manifolds with individual runners to each carb barrel. Neither the Alquati or the PBS manifolds are equipped with manifold heat. I believe that this is due to the fact that they were designed primarily for racing and the heat would hurt performance. In theory, the water jacket should improve drivability of the factory Fiat manifold, but Owners report that there are no real problems with cold starting or driving during warmup with either the Alquati or the PBS pieces.

One major difference is that the PBS uses the Weber IDF carbs and the Alquati uses the DCNF. Conventional wisdom dictates that because of the float placement in the two different designs that the IDFs are better for cornering with a longitudinal engine, and the DCNFs are better for transverse engines as installed in the Lancia Scorpion. I have friends with both types of manifolds and carbs, and under most driving conditions, they notice no drivability issues. Either manifold/carb combination should serve you well.

PBS manifolds are still available from PBS engineering and the Alquati may still be available from Art Bayless. Fiat factory manifolds are still around, but getting scarce. A few have come available from Australia and New Zealand where they were installed in some of the imported 131 sedans. Check out the "Parts Wanted" and "Parts for Sale" on Mirafiori or your favorite club magazine like FLU for current availability.

Air Cleaners

Probably no other part on a spider gets more attention than the air cleaner. If an owner has modified his car in any way, it is likely to be replacement of the factory UFO air cleaner with a shiny chrome aftermarket piece.

There is also a lot of information available about the relative merits and issues relating to the many options that are out there. I'll try to cover a couple of the variations and mention a few of the issues you might be concerned about when selecting one for your car.

The three parameters that need attention are: appearance, clearance, and effectiveness. Most people can't resist the idea of getting something shiny that is easy to install under the hood of their car. I've included a picture here of a factory air cleaner commonly called a "turtleback" above and also another creative solution from Bill Acklin's 2003 award winning car using crankcase breathers on each individual airhorn.

While it is usually appearance that moves us to replace the UFO, we quickly become aware of the issue of clearance. There is precious little room between any of the carb/manifold combinations and the hoods. Most critical are the 1608/flat hood and any 2L version. Generally if you stick to an air cleaner with at or less than 1.75" total height, you will be ok. OK may still mean a tight fit.

Even the factory turtleback with it's hard to find element is prone to vibrate on the hood or timing belt cover at various engine speeds. Aftermarket are available in stamped chrome, cast aluminum, or sheet steel. The vintage cast Redline covers on Red at left are getting rather hard to find as are the K&N filters though the elements are still available.

Thanks to Tom Nicotera for sluething out some compatible elements for the factory turtleback aircleaner. The cross reference numbers are:
Purolater: A50991 - Fram: CA340A - WIX: 42113
K&N: E1580 - Amsoil: TS20 - STP: SA340A You will have to oval the round filter to get it to pop into place, but it will fit fine.

There are a couple of things you can do to help maximize clearance. Some rubber engine mounts are shorter than others. It's possible to get an additional .25" by elongating the holes in the engine mounting brackets (be sure to drop the transmission mount a like amount). Also the large bump hoods have slightly more clearance, though most folks prefer the hood that comes with their car. If you have a 1800 or 2L engine in a small bumper car, you might gain a bit more clearance by mounting a crossmember for a 2L car. These let the engine sit a bit lower in the chassis and don't cost a huge amount of money to buy.

Some aftermarket air cleaners can be flexed or bent slightly down so they sit lower on the carb getting a bit more room. I might add here that there is another issue that prevents you from getting the carbs too short. The factory airhorns on the original Fiat 13/15 IDF carbs will be very close to the top of the air cleaner preventing you from lowering them too much. There are some aftermarket airhorns out there (abarth actually used a shorter version on the factory race cars inside an empty turtleback. Picture on left.) that are lower than the stock units. Thankfully the VW bug interest in the Weber IDF has prolonged the availability of rebuild kits and aftermarket parts for these carbs.

The third issue is serviceability. Some of the aftermarket elements are nothing more than sponge foam. These do little to filter out anything smaller than larger insects and the occasional semi truck. When shopping for your filter, try to consider the issue of element replacement. There are good elements and air cleaners available from K&N and Weber. You can check their websites for more information. Here again the VW crowd has helped us out. Pierce manifolds has a good selection of air cleaners for both the DCNF and the IDF carbs. Also nice shiny chrome bits for your standard single carb. Do a Search for their current web address.