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I wouldn't dismiss the curved stacks that quickly ... though I got slip-in style instead on one of my cars and a Euro airbox on the other ... yes, I know that added length between the butterflies and the valve likely has a greater beneficial effect than added length before the butterflies.

See the quote from a previous post of mine ... same torque - 160 ftlbs but torque arrived 400 rpm earlier with the extra length of the curved stacks compared to the Euro airbox ... rally car has the curved stacks ... street car has the Euro box.

It Sounds Like The Curved GTA Stacks Are Only Good For Some "Bling" On A Street Car.
FWIW, a few data points on similarly prepped 2 liter engines, same cams, same headwork, same ignition timing, both 45DCOE with almost identical carb settings.

1) Motronic pistons, 1" inlet tract extender, curved GTA replica air horns inside volume enlarged GTA replica airbox with GTA air intake: 160 ftlbs at 4800 rpm and 183 hp at 6500 rpm.

2) Motronic style pistons forged and lightened 1mm oversize bore, 1" inlet tract extender, late style Euro air box with openings enlarged and chamfered for 45DCOE: 160 ftlbs at 5200 rpm and 190hp at 6400 rpm. Main jet up one size.

Max torque is identical on both engines. It comes 400 rpm lower on engine 1, even though it has slightly less compression, heavier pistons and less swept volume than engine 2.

Engine 1 has longer tract length into the airbox and overall tract length to air intake snorkel is longer with much increased volume of airbox that provides a a Helmholtz-like chamber.

Engine 1 requires extensive modifications of the bodywork moving the inner fender on the passenger side to create clearance for the airbox and again clearancing of the body for the front snorkel (Giulia Berlina; not necessary on GT). There are at least 50 hours spent on fabrication and modifications on airbox, snorkel, bodywork, etc.
 

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Discussion Starter #23
Update: I Purchased Some "short (1")" Stacks & Mesh Filters From Pierce Manifolds (see photos). This Motor Is Going To Be Dyno'ed (winter/spring) So I'll Try No Stacks, Short Stacks, Mid Size Stacks With GTA Airbox, & Euro Airbox With No Stacks.
 

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