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So the 24V with big runners made a claimed 230 HP and my 12V with little runners made 260 HP which I know is genuine. You can have your big runners and I will keep my small ones.
BTW, my power curve was flat from 5800 to 7000 and my max torque was 250 ft lb.
 

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Don't understand your hostility to the notion of the larger runner. The figures am quoting are from Alfa so will be genuine too, although have seen the larger runners are 45mm not 43mm.
All the best with it.
 

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To the person who posted the original question, there are individuals on this thread who are offering you advice and who clearly have little or no experience building high output Alfa Romeo engines. They appear to be reproducing things that they have read and are drawing the wrong conclusions. Here is what I can tell you from experience:
My 2L Alfa Spider motor is an 8V Nord engine. The intake runners are 40 mm and the carburetor venturis are 36 mm. It makes 192 HP or 96HP/liter.
The 210HP 24V, 3L motor makes 210 HP or 70 HP/liter and it has 39 mm runners. I can guarantee to you that it can make much more power without increasing the runner diameter.
The 230 HP 24V 3L motor makes 230 HP or 77 HP/liter with larger runners and it is suggested that is the only difference between the motors.
Consider that Alfa changed camshaft specification for the 12V V6 motors at least three times without changing the part number and the only way to determine the ones that you have is to put them on a sophisticated camshaft measuring machine. On Alfa 2L Nord motors sold in the US Alfa kept the same camshaft for 20 years but changed the timing of them many times. Has anyone on this thread verified that the cams on these two 24V motors are identical and have identical timing marks?

Increasing the runner size beyond that which will make 96 HP/Liter to improve a motor that makes 70 HP/Liter makes little sense. Larger runners kill torque at low to mid rpm.
 

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Lower gearing in the 164Q and in the 164S partially compensates for loss of torque on low end caused by bigger intake runners on the 24v Q and larger Air Flow Meter on the 12v S me thinks. I had been my experience getting the stock Busso engines up on the cams about 3200-3500 rpm is where things start to happen.
 

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"loss of torque on low end caused by bigger intake runners on the 24v Q "

The Squadra dyno tests didn't really show that worth talking about, if at all. I'll have to look for them in my files.
 

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I've seen Alfa's power graphs for both versions of the 24v and never noticed anything but gains with the larger inlet runners fitted. Strangling an engine is not going to do anything but decrease output and vice versa. Only if flow diameter is not a bottleneck is there the risk of reducing power with larger bores - especially on carbed engines which require the airflow to properly suck the fuel out of the jet(s).
 

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Ed, just for the record, the larger inlet runners are the only difference between the normal and cloverleaf/Q4 engines and the sole reason for the increase in power. This is a widely known upgrade route power wise and totally works. My friend has a cloverleaf, which I have driven extensively and I have done the conversion on my 24v Super and got exactly the same power jump - all felt at higher revs due to better air flow.

Would be interesting to see what happens to the power output of your modded engine if larger inlet runners/higher flow breathing was fitted. Would it really lose power?
 

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Some previous posts on this subject.
FYI, Alfar7 won an SCCA championship in a GTV6 which he built himself and is an expert Alfa engine builder
 

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Interesting topic
It is clear that the large intake runners allow to gain 20hp on the 24v 164 engine.
Maybe for the 12v engine the big runners do not allow to gain power because the 12v engine has only 6 intake valves?! Oversized runners are maybe counterproductive in this configuration..
 

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Good topic and a few years back, I purchased an anemometer to check a few things:
At idle and with stock box and a k&n filter, what is the air speed between the airbox and maf?
What is the air speed with the airbox only and no filter (is filter restrictive)
What is airsped with NO airbox? (How restrictive are airbox and filter, can bottom of airbox be altered to allow better flow and maintain filtering?
With a cone filter replacement? (would 2 cones be better than an airbox and filter?)
Haven't gotten to it yet as I need an adapter for the cone filter and to fit the anemometer... and other priorities took hold but on my list of thingies to do this season.
 

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That sounds really interesting. Please do post your findings.
I used to have a K&N filter on my 24v 164 but sold it as a specialist workshop/racing team told me they flow better because they filter less. Didn't like the sound of that. The K&N definitely flowed better, noticeable performance improvement above 5,000rpm, similar in character to my later conversion to the larger 45mm inlet runners.
 

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I share an interesting case, a few weeks ago an acquaintance put his Alfa sz on the dyno, 2 sessions were carried out, the first with the air filter in place and the second without the air filter. the dyno showed a gain of 8hp with the filter removed.
 

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The K&N when properly oiled should filter just as well and still reduce drag. So sez the literature. I am interested in finding if 2 cone filters are better than the boxed filter as I expect the limited inlet of the box (snorkeled) may limit flow. So, more filter coverage area without a restrictive inlet should mean better flow. When everything else is done...hope to get to it.
 

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Well, that will only help if you can still draw cold air. If the cone sits behind the radiator and breathes from hot engine air, you will negate any potential gains. Hot air is less dense. More mass = more oxygen = more power.
 

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Keep in mind that the air coming through the radiator and entering the engine bay may end being I would guess ~150F or higher, and the ambient outside air entering the stock filter box through it's snout is more likely ~50-80F. Could make a difference if the cone filter draws in engine bay air, shroud or not.
 

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Could be. The ambient air drawn in is cooler for sure but the heat around the air filter can will probably warm that air before it gets through the maf. Could be we need some expensive setup to really know...thermometers placed at certain areas and monitored during an actual drive. That may be the only way to know the temperature of the air getting past the throttle. Beyond me but i will try to do the basic test anyway.
 

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There is a reason why the standard airbox has a snout to draw air away from the radiator and engine bay heat. This that is a crucial consideration in any air intake change.
By adding a K&N filter in place of the standard filter you get both the cooler air intake and less restrictive filter.
Am very aware of the claims K&N make of how well their filters filter, a reson I bought into buying one in the first place. Who has seen evidence of this? I haven't. And so I dropped my K&N filter, on the opinion of the race/car mod specialist (including mods for the Clarkson Top Gear crew) that they don't filter as well as the standard paper filter.

If you are going to replace the standard filter system, maybe try two conesor one large one, via pipe(s) long enough for them to be located ahead of the engine bay.
 

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Two cones were planned along with a shroud. A proper shroud that allows for air to be drawn in from beneath may still be beneficial but unless it is tried, it's all opinion. Time will tell.
 

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Agree is opinion until tested but well known benefits from not drawing hot air from engine bay and Alfa did go to the bother of making a cool air feed for the 164. As awkward as Alfa can be, they wouldn't do that for no reason.
If you have a chance to measure things scientifically that would be great information.
 
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