3.0 vs 2.5 Exhaust manifolds...

**RAGs** · #1 (**permalink**) 06-15-2007, 11:11 AM

Question ... is there a disadvantage to using the 2.5 manifold on a 3.0 Milano? The 2.5 seems sturdy, bolts on perfectly and give up just a little in terms of inlet diameter to the original 3.0.

My original manifold had a crack in the 2-3 Y, and I just happened to have a 2.5 set handy. Please advise.

Thanks.

Jose I · #2 (**permalink**) 06-16-2007, 01:44 AM

they are exatly the same, Alfa used alot of the same parts on the 3.0 that that they used on the 2.5.

**kredden** · #3 (**permalink**) 06-16-2007, 04:45 AM

I think there are other threads on this but I've measured both sets in the past and as far as I can tell they are identical. Others have come to that same conclusion as well. So go for it!

Jose, you didn't respond to my PM! What's up?

Kevin

Grant · #4 (**permalink**) 06-17-2007, 06:45 PM

I read in other threads that some people noticed the I.D. was actually different. Who knows with Alfa..

Potenziato · #5 (**permalink**) 06-17-2007, 07:11 PM

The 3.0 ones I have taken off look bigger than the 2.5 ones. Of course, sometimes the 3.0 ones have been swapped for 2.5 manifolds along the life of the car.

I have a spare driver side 3.0 manifold that needs to be drilled because of a broken stud. I notice the 3.0 manifolds are getting harder to find used.

**RAGs** · #6 (**permalink**) 06-18-2007, 10:19 AM

All,

Thanks for all your thoughts. I measured the copper gaskets that came with the 3.0 engine set against the 2.5 manifold and they were pretty close. All bolted!

ULTRALINK A75 · #7 (**permalink**) 07-03-2007, 07:23 AM

The 3.0 manifold are much bigger in diameter . You will lose power .

**Alfar7** · #8 (**permalink**) 07-03-2007, 07:51 AM

They are identical other than parts numbers. Heads port size is identical as well between them, intake & exhaust. Valves seats & bowls are bigger in 3.0.
Don`t you hate it!!

ULTRALINK A75 · #9 (**permalink**) 07-03-2007, 09:04 AM

Are not the same Alfar7 !! Are smaller in diameter and he will lose power .

Opposite they would be desirable . The 3.0 manifolds in a 2.5 engine .

junglejustice · #10 (**permalink**) 07-03-2007, 09:41 AM

Yep, they are NOT the same - I have a set of each sitting right here and have mic'ed them - they have separate part numbers as mentioned as well! The difference is marginal but it is there - the 3.0 manifolds are larger.

In any event, the stock manifolds are crap compared to a nice after-market tubular header!

**kredden** · #11 (**permalink**) 07-03-2007, 10:36 AM

I've measured both sets numerous times and always end up showing that they are the same. Another guy I work with has done the same to his sets also showing that they are the same.

JJ, if you've mic'd them what is the difference in size? Are you sure your not mic'ing a clean set and a set with some carbon build up?

Anyway, if it takes a mic to tell the difference in size (if there is indeed any) then I can't imagine that you'd get any noticeable power gain/loss from using the opposite set.

Kevin

slyalfa · #12 (**permalink**) 07-03-2007, 11:48 AM

The info I got from APE is the 3.0 are thiner (and crack very easy vs the 2.5)
I cracked many untill I added a bar under my car so the down pipes can not touch first.

I think if you weigh them you will see there is less there. the outside is the same size. and the ports might even be the same but they are thiner on the insides. I had a pair of busted 3.0 abd 2.5 at one time and you could see the difference where they broke.

**RAGs** · #13 (**permalink**) 07-03-2007, 01:31 PM

All,

Don't laugh!!!

I did a basic (non-scientific) volume test - capping the bottom of each manifold and filling with water. The volume of the full 2.5 manifold poured onto the 3.0 with room to spare. Water from the full 3.0 overflowed the 2.5 by quite a bit. (I guess I could have measured the fluid)

The long and short is that it does seem that although the external dimensions are similar, the 3.0 has a higher capacity and I assume flow - and the thinner walls might be more prone to cracking.

As I mentioned in the beginning of the thread, my right side manifold was cracked. Does anyone have a 3.0 spare for the right side? I'm in southeast USA. Thanks in advance.

ULTRALINK A75 · #14 (**permalink**) 07-05-2007, 03:46 AM

Look at E-BAY . Key words ALFA MILANO

**Alfar7** · #15 (**permalink**) 07-10-2007, 07:49 PM

[QUOTE]Anyway, if it takes a mic to tell the difference in size (if there is indeed any) then I can't imagine that you'd get any noticeable power gain/loss from using the opposite set.

[/quote]
Kevin you are totally correct.