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Discussion Starter · #1 ·
This is my first post here and I am somewhat new to Alfa Romeos in general. I am going to be buying my friend's 87 Milano Platinum 2.5 V6 within a month. Like many of you who are crazy about these cars, I am already planning upgrades. I know my friend had a new engine built for it and I will find out the specs of it soon.

For now, My plans are cleaning up the interior, a good tune up, and CSC Headers. Along with the headers, I would like to upgrade the intake to even things out. I have seen a few 12V builds that have a 24V intake plenum and runners (I'm guessing). I would like to do this, but I am not sure what the constraints are for the swap and what it entails. Is it possible to do this swap with basic modifications? What about the TPS sensor? Do I need a Standalone ECU?

Maybe this has been discussed previously, but I have not found anything on the 24V plenum and intake swap.

Thanks
 

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What is your reason for wanting to use a 24v plenum? Especially as you’re not sure what the engine specs are currently? Buying a Milano is exciting, but I’d figure out what you’re working with first before agonizing over engine modifications. Baseline first, then tune up as you mentioned (if it needs one). Go from there.
 

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Discussion Starter · #3 ·
What is your reason for wanting to use a 24v plenum? Especially as you’re not sure what the engine specs are currently? Buying a Milano is exciting, but I’d figure out what you’re working with first before agonizing over engine modifications. Baseline first, then tune up as you mentioned (if it needs one). Go from there.
I read somewhere that the later model Busso 24V intake plenum has more volume and the runners have a bigger bore, therefore allowing more air into the engine. I wanted to know if anyone else had experience with that. Bigger does not always mean better when it comes to intake and exhaust.
My friend told me that it is a "racing" motor, but that could be many different things, he's also said that it's a stroked 2.5 to 2.8. I'll get the full specs from him soon. I know it has a racing clutch and flywheel, the transmission syncros were replaced about 4 years ago, as well as all the usual suspension goodies, Koni yellows, sway bars, poly bushings. He has had it for 5 years, and his dad, 20 years before that, so there's plenty of records to go through.
I will definitely do the usual air filter, spark plugs, wires, cap, rotor and oil change that I do with all the cars I buy. I'll probably check the fuel lines and hoses also, as I've read those can be problematic in most old Alfas. I'm just always wondering what else can be done. I figure upgrading the intake when I upgrade the exhaust would be a good idea.
 

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It's not impossible, but it's not a drop in either. 24V engines were mounted transversely in the engine bay, so your plenum will hang off to one side if you do the conversion. The 3.0 12V Milanos (I have one) the plenum (as far as I understand) is certainly not the bottleneck to the system (same part as 2.5, however air flow meter is a different part number).
 

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Instead of doing that, cut open the bottom of your plenum and improve the bell mouth and lower the floor a bit or have a machinist make a new plenum floor for you. Lowering the floor will increase the plenum’ s volume. Port the runner as well. Even 2mm in diameter is good enough. Then contact Al Mitchell for a plug and play MS ECU.
 

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Per Jim K's V6 book, the intake runners are the limitation on the 2.5 / 3.0. The 2mm porting suggestion sounds about what he recommended. Too big is not good either. This was for a 10.5 / 11:1 normally aspirated formula. His thoughts on headers are that no commercially available ones were really right for the project. They look cool, but not a huge bang for the buck.

Based on your description of a modified 2.8, you probably will want to see what you have before modifying further.
 

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Put your $'s into making the thing handle and brake well. Alfa engines can take a huge amount of abuse, if well maintained, so you can run them hard for longer than you will be able to sustain the effort, and your extra cornering speed and braking ability will show all your friends whose boss.

If you are intending to take them on in the 'oh so American' traffic light GP, you have bough the wrong car. Grandmas Honda Civic will probably beat a 75/Milano
Pete
 

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The Milano handles reasonably well. If you get euro bumpers and move the battery to the back, even without touching the suspension the handling will improve.

Even with engine mods you'll still lose to a Civic EK with a K24, so I'm pretty sure nobody here is talking about drag racing anything.

A little bit of extra power is always nice especially if it comes with a bit more revs. The Alfa V6 sounds great at 7K rpm and according to JimK it sounds even better at 8K rpm. One thing I love about my 24V is it is so eager to rev, and the sound is unmatched this side of a Ferrari.

Although I wouldn't sacrifice too much of the engine's original sound to gain the extra power. Modify it within reason.
 

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Discussion Starter · #9 ·
Per Jim K's V6 book, the intake runners are the limitation on the 2.5 / 3.0. The 2mm porting suggestion sounds about what he recommended. Too big is not good either. This was for a 10.5 / 11:1 normally aspirated formula. His thoughts on headers are that no commercially available ones were really right for the project. They look cool, but not a huge bang for the buck.

Based on your description of a modified 2.8, you probably will want to see what you have before modifying further.
Ahhh good to know. My friend has Jim K's book that I will be getting with the purchase, so I will be reading that heavily when I get it. Sounds like a lot of my questions will be answered reading it.

Put your $'s into making the thing handle and brake well. Alfa engines can take a huge amount of abuse, if well maintained, so you can run them hard for longer than you will be able to sustain the effort, and your extra cornering speed and braking ability will show all your friends whose boss.

If you are intending to take them on in the 'oh so American' traffic light GP, you have bough the wrong car. Grandmas Honda Civic will probably beat a 75/Milano
Pete
I know it already has Koni sport shocks, Bigger sway bars, and lowering springs in the back, but those things might be a little tired. I definitely want a good performance brake kit for it, because stopping is important. I also need to get some good tires because the Hankooks on there are getting bald. There's definitely lots of work to be done, but it's in pretty good shape for 175k.
 

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The Milano handles reasonably well. If you get euro bumpers and move the battery to the back, even without touching the suspension the handling will improve.

Even with engine mods you'll still lose to a Civic EK with a K24, so I'm pretty sure nobody here is talking about drag racing anything.

A little bit of extra power is always nice especially if it comes with a bit more revs. The Alfa V6 sounds great at 7K rpm and according to JimK it sounds even better at 8K rpm. One thing I love about my 24V is it is so eager to rev, and the sound is unmatched this side of a Ferrari.

Although I wouldn't sacrifice too much of the engine's original sound to gain the extra power. Modify it within reason.
Well for a start the PO's looking at buying headers which is just a waste of money and time ...

Pete
 

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Only after properly modifying the runners does the plenum become an airflow restriction.

I took my modified top end to an airflow bench. The head actually flowed better, in CFM, with the modified runners, it lost CFM when the plenum was added.

Now, that is not the be all end all of the issue. The ports and runners are "lazy", not having the velocity that we would have liked. The engine is going to be less than it could be at lower rpm.

I posted the results in thread somewhere.
 

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Well for a start the PO's looking at buying headers which is just a waste of money and time ...

Pete
Not sure about which headers the PO is going to get. But about 15-20 years ago someone dynoed a Milano 2.5 with CSC headers and there were gains. Can’t argue with empirical data. The $/bhp may not be great but there will be gains.
 
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This is my first post here and I am somewhat new to Alfa Romeos in general. I am going to be buying my friend's 87 Milano Platinum 2.5 V6 within a month. Like many of you who are crazy about these cars, I am already planning upgrades. I know my friend had a new engine built for it and I will find out the specs of it soon.

For now, My plans are cleaning up the interior, a good tune up, and CSC Headers. Along with the headers, I would like to upgrade the intake to even things out. I have seen a few 12V builds that have a 24V intake plenum and runners (I'm guessing). I would like to do this, but I am not sure what the constraints are for the swap and what it entails. Is it possible to do this swap with basic modifications? What about the TPS sensor? Do I need a Standalone ECU?

Maybe this has been discussed previously, but I have not found anything on the 24V plenum and intake swap.

Thanks


I think we need pics!
 

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Instead of spending $BIG on CSC headers for a 5HP improvement you might consider the much cheaper Magnaflow down-pipe section which will bolt to the stock manifolds, which will then allow a more overall free flowing system. I know in the past many people have verified that 3.0 manifolds are in fact larger, so this may be another step. Not a heck of a lot to be had playing with the wasted gases though - better to get more volume IN. Camshafts are your friend and will yield the best $/hp in my opinion; there are many people re-profiling camshafts and you can send yours or some spares to have this done (or fork out for some new/used ones from catcams, C&B etc). Compression bumps help this engine come alive also, mine is 11:1 and its quite gnarly coupled with many other mods. The 164 intake is much better designed than a stock Milano, however its also FAR from ideal with the throttle body at one end; couple this with the fact that it will point the opposite direction you need, I would imagine this would be a fair bit of work unless you can just chop and reweld (if you have the equipment). As other have said, JimK's book sites many times on the bottleneck in the stock intake, so every little bit counts here. Just so your aware, it took me an agonizing 12 hours to enlarge my factory runners to 38.5mm from the original 35ish - the 164 intake is ALREADY 38.5mm, so choose your poison!
 
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I picked up a brand new set of the Magnaflow downpipes/high-flow cat for under $400 shipped from a Canadian supplier, so it's worth doing a search for the best price before you buy. Haven't installed it yet, so I can't comment on gains. I think Centerline claims +10 hp on a Verde, or thereabouts.
 

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High Performance Intake Runners for the Alfa Romeo 75 and Milano (additiverestoration.com) I had these Intake runners commissioned by Steve Dibdin @ Additive restoration 2 years ago and they work a treat, they are available in different sizes and golf ball dimpling ... I chose a 40mm to 37 mm taper... I welded 40mm spun aluminum weber velocity stacks nearly flush into the plenum floor (picture is pre welding!) ... Add 302 Cat cams from Andy @ Performatek | Alfa Romeo Parts and Advice ... a .050 milling of the head for compression bump, deshrouding the valves, a set of International Auto SZ headers, larger injectors and air flow meter with an adjustable fuel pressure regulator and heavy duty timing belt kit...In my 3.0 with a platinum 4.10 LSD this all equates to a wheel spinning horsepower that runs to the redline with a visceral shriek that no civic could possibly match.

Santo Spadaro
Milano Platinum... 750 Giulietta Sprint Veloce
 

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@spinta volante Nice! Wondering what the impact would be without the increased compression? Might have to just try and see...
 

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Discussion Starter · #20 ·
Thank you everybody for your input! I like the look of those cone-shaped intake runners!

The belt upgrade was engineered by Alfonso Ciardullo. It is a direct bolt on and very simple, elegant and effective... turn the engine backwards without ill effect
What is the benefit of this upgrade over the stock cam belt?
 
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