Last project of the year before I put the car away for a winter nap. If you are the patient type and don’t mind some hacksawing and grinding this project may appeal to you even if you don’t weld (all welding can be done off
As one gazes at our otherwise beautiful 12v engine compartment
, don’t you find the clunky cast iron exhaust manifolds somewhat of an eyesore? Besides being ugly and rusted, the flow is restrictive. Alfa redressed the problem on the 24v engine with strikingly beautiful 1-1/2” id tube headers in V2A stainless (a heat shield on the 24v model hides the front headers from plain view). Alfa subcontracted these to Zeuna-Stärker Augsburg which makes exhaust parts for many marks including BMW motorcycles and Ferrari. Although the tubes are not of tuned-length, the workmanship is outstanding. Wouldn’t it be great to graft these beauties onto our 12v engine using the stock 12v flex pipes and cat?
did exactly this some time ago and this is what inspired me. Others
have done the conversion as well. I’d like to share here the steps I took (photos show only front headers but the rear is the same, easier in some respects, but harder to install because of the cramped space).
first some general information:
-id of the 12v head port is approx. 1-3/8” (1.48 sq in)
-the 24v oblong tube measures id 1.04” x 1.92”, reshaped into a round form the id becomes a little bit larger than 1-1/2” (1.77 sq. in, or ca. 20% increase; however the displacement increase (internal size of the whole manifold) is a whopping 60%+)
-id of exit side of headers is 2”; id of stock 24v downpipe is 1.9” while id of stock 12v downpipe is 1.75”
1) purchased a set of second-hand 24v headers from BBer Alfaguy35. They look awfully black but they’re AISI 304 stainless and will clean up nicely.
2) sawed off tubes: on the original design the tubes are set about halfway into the flange and welded from the inside leaving a stepped edge. The first task is to to “skim” the tubes from the outside of the flanges with a thin hacksaw blade.
3) reshaped oblong into round (almost round is fine); beforehand removed the 3 heat shield studs, any extra metal that was an impediment to reshaping, and the reinforcement plates on the cylinder no.6 tube (you will be spared this prep work on the rear headers). (radiator clamps in photo protected “Zeuna” badge from getting accidentally detached)