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Most of us have abandoned the curved velocity stacks in favor of the newer "mushroom" horns... flow bench test show these to be better.
see:
Pegasus -Air Horn, 45 & 47mm General Purpose - 40mm Tall
There is no doubt in my mind that the full radius horns without mesh will flow better than the original on the flowbench. Whether the engine will put out more horsepower with them, especially with an original style cold air box remains to be seen.

Replica curved airhorns look like the are likely to flow better than the originals but they won't fit the box w/o modification - a lot of 1600's in European Historic racing are in fact using these with the screens removed w/o airbox.

Generally 105 type engines seems to respond well to a lengthening of the intake tract. Also, the straight horns put the bellmouth very close to the outer wall of the airbox which may interfere w/ flow.

Running short stacks (non-full radius) w/o airbox definitely reduces the torque low down noticeably - didn't drive the car enough with them to ascertain the top powerband. Anyway, I've had good results on the dyno w/ the original curved stacks and airbox on a 1600 twinplug.

Also, I wonder whether slip fit vs. non slip-fit horns give better overall flow. Slip-fit will reduce the barrel diameter of the carb somewhat, but the ridge created by the auxiliary venturi is essentially completely smoothed, thus reducing turbulence in that area of the carb.
 

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I'd be interested in final costs as well--interesting thread
 

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Discussion Starter · #43 ·
GTA Airbox and Snout update

To all interested parties here is the latest information. I have taken delivery of the first snout and installed it in my GTA. The fabricator has made a prototype of the airbox but has no pricing and is redoing his tooling. To complete the airbox the fabricator needs to make the plate that bolts to the carbs and the straps.

Scott Gray Loaned his airbox and snout to the fabricator to make the parts and will be the one selling the parts. I will not be selling Airboxes or snouts!

The parts are not going to be low cost due to the high labor content. There may be some fitment issues with other (non GTA) Alfas and Scott does not want to sell individual parts like straps or sell the snout for other models.

Thanks to everyone that has responded with interest and encouragement. I did not set out to be in the airbox business and was just hoping to reduce the tooling costs. I know everyone wants to know the cost. I don't what the final costs will be but to ball park a rough estimate the total cost for both parts will be north of $5500. I hesitate to throw out this price but I doubt it will be be less and if it exceeds your budget then you can make other decisions. To those that did not have a heart attack at reading this price. The parts are world class and worth the wait. When I have the final airbox I will post the photos. I will ask Scott to post his contact information.
 

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air boxes

No heart attack, but I applaud your enthusiasm and can't wait to see you tooling this car out on the track Bob.
 

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I'm pretty sure you could have bought a whole new GTA Stradella off the dealer floor in 1966 for right around that figure!
Or a well used GTA racer in the 1970s.
 

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As I recall, the AROC newsletter had an article on the new GTA.

Price was about US$5500, and the factory race-prepared one was almost $7000.

And the price of gold was $35 per ounce.
 

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Just a small reference, we make the fibreglass Airboxes, and I can tell you that
to fully build one. with 5 moulds (that require periodic maintenance),
it requires 20 hours to produce each one, so an ally one is bound to take more time as
the shaping and welding is not exactly a 'rush job'.

Making parts, is not only for sport and enthusiasm, there has to be some profits involved too.

Are the ally boxes still being made? I mean, this post is upwards of 12 years old!
Regards, Alberto
 

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No I think. Roman Tucker did that restoration on RHD GTA 752648 and as they were bringing back from a wide bodied C Sedan GTAj type to accurate 1966 as out of AD they needed a period correct Alu Air Box. I think Tucker built the box as a 1 off. Most of those alu boxes failed in era from fatigue and were replaced in 1968 when the FRP air box that Alberto reproduces was homologated. I had an original FRP (fibre reinforced plastic) without door. I used Albertos accurate repro to make an accurate well fitting (from 2 pieces) door. I then used the original box to dimension the fresh air insert that the original box has but the repros didn't have (at that time).

Ken
 

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OKP sells an aluminum replica ... not sure whether the numbers and letters should be on the aluminum version though ... always assumed the 68 indicated the year of the first fiberglass version.

OKP GmbH
Just for the record. “Presa d’aria dinamica” (dynamic airbox) was developed for Alfa Romeo TZ and F3 engine, available with 10510.08.108.00 rep. code. In 1966 season it was used on GTA cars (first appearance 20 March 1966, at Monza with 40 DCO3 Weber carbs), and later in December 1966 it was homologated with F.I.A. J extension as 1395 C/V homologation sheet (10532.08.204.00 rep. code), for both, 652.08.002 Weber 40DCO3 airhorns and 652.08.011 Weber 45DCOE14 airhorns.
Early version produced at Arese factory was in aluminium and later, made in Autodelta at Settimo Milanese was produced from GRP (fiberglass). Both versions had engraved code on upper side. Airbox was used with straight and also curved airhorns, without filters and was protected with net on snorkel entrance and airhorns sometimes. Here are examples of early (‘66) type, ’67 aluminium versions (coloured in black, original ones were in nude sheet), and GRP replica with curved horns covered with net. It is visible also the net cover of air intake of the snorkel.
 

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Post #55 makes multiple erroneous statements as well as showing pictures that show non-original parts which include but are not limited to the following:

  • First known GTA cold airbox in a race at Targa Florio in 1965 Targa Florio 1965 see post #8
  • airbox and airhorns were not available for 40DCO3 but for 40DCOE
  • 40DCOE was not for GTA which always had 45DCOE14 homologated
  • preso d'aria picture airhorns are aftermarket not Alfa or Autodelta
  • pad 1 picture airhorns aftermarket
  • aluminum box likely had no numbering on box - never seen one with it and I have seen many ...

Original Autodelta airhorns below - 45 DCOE

1629679
 

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Post #55 makes multiple erroneous statements as well as showing pictures that show non-original parts which include but are not limited to the following:

  • First known GTA cold airbox in a race at Targa Florio in 1965 Targa Florio 1965 see post #8
  • airbox and airhorns were not available for 40DCO3 but for 40DCOE
  • 40DCOE was not for GTA which always had 45DCOE14 homologated
  • preso d'aria picture airhorns are aftermarket not Alfa or Autodelta
  • pad 1 picture airhorns aftermarket
  • aluminum box likely had no numbering on box - never seen one with it and I have seen many ...
Original Autodelta airhorns below - 45 DCOE

View attachment 1629679
Targa Florio 1965 event was second apparition of GTA 1600 ever in competition. The car was not yet homologated and started with private team Scuderia Pegaso, with Alessandro Federico and Mario Araujo Cabral as drivers, in Group 6, Prototype cars. Federico had accident in 4° lap and the race was abandoned. The car started with # 166, and in base of existing photos, without “shaped air intake”, term used for air duct used for direction of air flow. As the car was still Prototype there was no oblige for homologation of similar accessories and it could be easily used for the event. In May, homologation for Group 2 finally arrived and in Nurburgring, Mugello and Trento-Bondone races airduct was observed on 613007, but it was not Presa d’aria dinamica in its known form, but ‘shaped inlet’ (105.32.08.205.00) with different proved solutions. Precise answer to that question was released by Teodoro Zeccoli in his interview to Maurizio Tabucchi, 21. Jun 1991, and is referred in the book ‘Alfa Romeo GTA “leggera” e vincente’, on pages 61 and 62. In the same interview, Zeccoli underlined as curiosity, that for the event of 19-20 March race at Monza circuit (4 hours Jolly Club on 10 km track) the known form of dynamic airbox was used but with old type carburettors, 40DCO3, without explanation for that choice. In all other events the 45DCOE14 were used instead. This ‘curiosity’ is reported in the same book at page 62, and in full form in Zeccoli’s interview to Tabucchi in 1991. The first ‘official’ use of dynamic airbox is stated for Jolly Club Monza race, where 613007, 613009 and 613073(#62, #63, #64, official Autodelta cars) were observed vith ‘shaped air inlet’ and dynamic airbox mounted. Your statement is interesting and with reliable sources cited, it might be precious. So, please list your sources. For numbers on the top side of airboxes (metal and GRP ones), I accept and respect your experience, but believe me, also I have seen more than one airbox, and all ‘true’ ones (’66) were numbered. Airbox with installed curved airhorns is GRP replica, and I have clearly indicated that.
 

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