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Good points, although I won't rule out the street-cred derived from a cool looking engine. In terms of effectiveness headers can offer incremental horsepower advantages. You may see some small benefit on a stock engine but where these kinds of incremental contributing factors come into play is when you are building a fully-built motor. With the right combinations of head-work, cams, high-comp pistons, ignition, carb mods, lightweight flywheel, balanced bottom end, etc., etc. you can build a very decent 160-170hp 2 liter Alfa Nord engine that will be a real blast to drive. It won't be a state-of-the-art race engine but you'll nonetheless have a very satisfying increase in hp that will nonetheless run quite happily on pump gas and return 21-22mpg.

Several years ago I think George Willet commented that slightly modified stock, cast-iron headers were entirely good---up to about 140-150hp when, along with other required mods, proper headers came into play. This seems about right to me.

Well, we're all lookin' for that secret sauce ingredient!
awhile during the early years of the BB, simon anthony and big thanks to peter for setting up the magnaflow alfa dyno days at his facility.

somebody that was keeping track said it was the highest powered nord of the day. spica on stock manifold, 133whp depending on how you want to calculated the losses 155 to 165hp at the crank. note the car car was not dialed in yet as you can see by the A/F readings. Ive later added the SS exhaust since the vid.

you can hear how much smoother the cast irons sound over the tubular headers of the others


dyno graph, off the shelf specs and my own secret sauce porting. here:

https://www.alfabb.com/bb/forums/gt-1963-1977/26955-74-gtv-dyno-results.html
 

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Here are some header HP numbers from "The Vandenberg Papers" published in the Alfa Romeo Owners Club Technical Notes from the early 1970's. There were many dyno tests run by Dave Vandenberg Import service in Belmont California using the Hasselgren Engines dyno.

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Looks like a good project for someone who really wants an accurate number.:wink2:
The drop in performance when Alfa switched to the one piece manifold and the dyno results published by Shankle for his headers points to a difference of about 10 HP.
That is also backed up by theory - length of header tubes, speed of sound in the pipes, rpm.
 

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Here are some header HP numbers from "The Vandenberg Papers" published in the Alfa Romeo Owners Club Technical Notes from the early 1970's. There were many dyno tests run by Dave Vandenberg Import service in Belmont California using the Hasselgren Engines dyno.
anyone notice what happens on the technical notes by replacing the spica with webers? :)
 

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According to the table for exhaust systems at 5000 rpm a '76 made 109 HP and a 77 made 118 HP. The exhaust manifold was the same. Where did the extra 9 HP come from?
What is interesting is that the 76 had cam LC's of 114. 114 and the 77 had 102, 102. My guess is the difference is cam timing and not exhaust system.
 

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At the end of the day.... when god judges you, to tell the truth ....can you really differentiate the difference in a street drive?
Tom, I’m not the best person to ask that...in the past I’ve lost my license twice ��

How about that removal of the engine fan?
Lol... now you know why the Gta and gtams had the stubby fan option.

Disappointed with the test gains... Shankle gained 7hp on his catalogues I recall since he wanted to sell more electric ones :)
 

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Truth be told it takes a real pro to translate 8-10 HP in competition performance. The trick here is anyone can spend money ...but to spend it wisely takes talent and a little experience. So speaking as a fool who did all this nonsense, 5,10,15 even 20 HP on your street car means squat, seek life elsewhere. I now put money into drivability, tuning suspensions, lightning flywheels that were designed for a family sedan, synchronizing first gears, lightening the gearbox rotating masses, better braking, well-done cosmetic enhancement...ah it's just an old near 70 guy thinking out loud..
 

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My experience is that the best improvements come from the loose nut on the end of the steering wheel. And the track time and training that takes is a lot of fun as well. When I was racing, I always noted that my last few laps were always faster than the first ones, on any track.

Robert
 

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Truth be told it takes a real pro to translate 8-10 HP in competition performance. The trick here is anyone can spend money ...but to spend it wisely takes talent and a little experience. So speaking as a fool who did all this nonsense, 5,10,15 even 20 HP on your street car means squat, seek life elsewhere. I now put money into drivability, tuning suspensions, lightning flywheels that were designed for a family sedan, synchronizing first gears, lightening the gearbox rotating masses, better braking, well-done cosmetic enhancement...ah it's just an old near 70 guy thinking out loud..
This "old" 1960s guy is with you.
But in a 101 Spider the mechanical fan robbed HP and worse--was noisy.
Unless you have a show car, get rid of them.
The aluminium ones look good, mount one on the wall of your shop, or den.
:)
 

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Hi Jim,

Have you measured top to bottom or side to side?

I have twos sets not mounted on the car and another one mounted that I can't measure. To me it looks like the inside diameter of the tubing is about 38mm. However, there is some crude porting done that is very visible on my NOS set ... and indeed 1 and 2 have the 40mm dimension top to bottom on both sets. the side to side dimension on the used set is consistently 38mm and varies from 37 to 38mm on the other set. My money is that the apparently different size primaries are attributable to the porting of the flanges rather than due to differnt pipe diameters.

IMO 38mm works better on the street than 40mm or above and it may significantly lower the rpm when max torque comes in.

Re: some of the comments on drivability ... putting 1600 GTA headers with a 2 1/4" GTA exhaust on an otherwise very stock Giulia Super made a huge difference in bottom-end torque and drivability ... right up there with with close ratio box, lightweight flywheel and good shocks ...

Shankle/Centerline headers (38mm) - not the replica GTA type which is 40mm - work great on a 2-liter, especially when combined with an improved merge collector and a good exhaust with 2 1/4 or 2 1/2 diameter. However a ready made Alfaholics set-up may be a lot easier ...

Here are the primary diameters of my GTA headers. This might explain why Classic Alfa offered "big tube" 40mm headers (presumably from CSC). When I get a chance I'll measure my Alfaholics headers for comparison.

#1 40.08 mm
#2 40.11 mm
#3 37.00 mm
#4 37.00 mm
 

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I have twos sets not mounted on the car and another one mounted that I can't measure. To me it looks like the inside diameter of the tubing is about 38mm. However, there is some crude porting done that is very visible on my NOS set ... and indeed 1 and 2 have the 40mm dimension top to bottom on both sets. the side to side dimension on the used set is consistently 38mm and varies from 37 to 38mm on the other set. My money is that the apparently different size primaries are attributable to the porting of the flanges rather than due to differnt pipe diameters.
I measured the .o.d. of the primaries about 5in down from the curve. I'll be happy to do some more measuring if you want. BTW: I imported these headers about '73 or '74. The guy I bought them from was pretty well connected with Alfa so I think he maybe was buying direct, although at the time Alfa stil had stocking part numbers for the headers along with most other GTA and even TI Super specific stufff that could just be ordered at any dealer.

IMO 38mm works better on the street than 40mm or above and it may significantly lower the rpm when max torque comes in.

Re: some of the comments on drivability ... putting 1600 GTA headers with a 2 1/4" GTA exhaust on an otherwise very stock Giulia Super made a huge difference in bottom-end torque and drivability ... right up there with with close ratio box, lightweight flywheel and good shocks
Coming from someone who won his class in a TI Super against some respectablly fast competition in the '08 Carrera, I'd say this is a pretty solid observation. Your secret sauce works. >:)

Sadly the GTA headers require some modification to fit a 2 liter Alfa motor. Nonetheless, they are such a good design that I've wondered why none of the vendors haven't convinced their supplier to make authentic vintage-style GTA headers that will fit a 2 liter's taller block. I bought the Alfaholics exhaust for my Super because it was stainless and the headers were GTA style and the exhaust dia was 2 1/4" or 2 1/2". I'm very happy with the way it works with my version of John Trevey's "in the style of" version of your Rally motor.
 

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This "old" 1960s guy is with you.
But in a 101 Spider the mechanical fan robbed HP and worse--was noisy.
Unless you have a show car, get rid of them.
The aluminium ones look good, mount one on the wall of your shop, or den.
:)
removing the fan might be ok in balmy BC summers but not so well in socal 405 traffic jam... :laugh2:

ive notice just removing the fan shroud will affect the cooling in rush hour traffic on a mod motor with more heat generated.

what next? electric water pump and axle driven alternator so it can read higher on dyno? lol
 

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Mechanical fans move little air when you need them most - when the motor is turning slowly. They move lots of air when the motor is turning fast but then you normally have high air speed. A good electric fan will move lots of air when the car is stuck in hot traffic and it will turn off when you are moving quickly and when you can the extra HP.
It should surprise no one that modern cars use electric fans.
 

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Talking about primary tube diameters, look at Giulietta Veloce headers, they are absolutely tiny, does smaller diameter add a performance gain in 1300 cc engines. Most suppliers claim their headers fit, 1300, 1600 1750 and 2000cc engines, and no doubt they fit, but is a larger bore primary overkill on a small displacement engine? I know in race engines a smaller engine might benefit from bigger diameter primaries, I suspect, at least at the time Alfa knew what they were doing with veloce headers. Just wondering.
 

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Discussion Starter #119
Just as a side note for the original question regarding engine note.

I finally broke in my new borla muffler and the car sounds a lot better! Especially in 3rd gear!

I highly recommend people allow 300-500 break in miles on a new muffler before making any decisions regarding further modifications.
 
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