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Discussion Starter · #1 ·
Hi all,

I know this is a topic that has been discussed here and there, but I'd still love to get some more thoughts on this matter. I own a US '86 GTV6 and live in the Netherlands. I absolutely love the sound of my GTV6 cat still in place, mid muffler and Ansa rear.

I'm planning to do an engine overhaul after this season and got the opportunity from my mechanic to put in a 3.0 liter. I wouldn't mind a little more power but just trying to judge from videos it does seem that the sound is quite different, lower and not as revvy.

Can anyone chime in that did the swap and noticed that the sound changed? I'd love to hear your thoughts.

Best,

Maarten.
 

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If you have an easy option for a 3L, go for it. I’m personally not so keen on the converted 164 engine install but if it’s an original transaxle car 3L, then totally do it. The costs of overhaul are the same and it’s a significant power upgrade.
 

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The power increase more than makes up for the slight loss of edginess and pitch, and also to note that different exhaust systems produce quite different results. The factory OEM, well broken in sounds great on the 2.5. The 3.0 engine still sounds amazing. The usable power increase between stock-to-stock feels much more significant than the numbers would suggest and even a slightly modified 3.0 goes on from there. My old Italian mechanic, Carlo Durante at Alfa of Tacoma (RIP) and builder of many Alfa and exotic engines preferred the 2.5 for sound and balance. He felt there was a very small difference in the balance of the engine no matter how carefully he built the 3.0. Of course he sensed things that I would never detect. His GTV6 and Milano kept their 2.5 motors, liking that engine more than many/most exotic powerplants (and he drove all of them). So you can’t go wrong.
 

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I would go for the 3.0 as well. It's not so much the greater horsepower as a GTV6 will be slow with either engine compared to modern cars, but the torque curve make the 3.0 easier to drive in everyday traffic.
 

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If you choose to go with the 3.0 liter conversion do the round toothed timing belt mod as well. Alfa actually sells the parts to do the 3.0 liter engines (the right hand head is different on the Milano and later 3.0 liters than the 2.5s) so you can get the necessary sprockets and pulleys straight from the OEM. If you convert the 2.5 you'll have to get the kit from Chris Snowden Racing (CSR, alfettagtv6.co.uk) and it runs about 860 pound sterling = $1,122.91 at current rate of exchange
 

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Hi all,

I know this is a topic that has been discussed here and there, but I'd still love to get some more thoughts on this matter. I own a US '86 GTV6 and live in the Netherlands. I absolutely love the sound of my GTV6 cat still in place, mid muffler and Ansa rear.

I'm planning to do an engine overhaul after this season and got the opportunity from my mechanic to put in a 3.0 liter. I wouldn't mind a little more power but just trying to judge from videos it does seem that the sound is quite different, lower and not as revvy.

Can anyone chime in that did the swap and noticed that the sound changed? I'd love to hear your thoughts.

Best,

Maarten.
I have the same exhaust set up as you but with a 3 liter conversion. There is a slight change in the exhaust note from comparing it to the 2.5 stock engine, but you have to listen carefully.
 

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Discussion Starter · #7 ·
The power increase more than makes up for the slight loss of edginess and pitch, and also to note that different exhaust systems produce quite different results. The factory OEM, well broken in sounds great on the 2.5. The 3.0 engine still sounds amazing. The usable power increase between stock-to-stock feels much more significant than the numbers would suggest and even a slightly modified 3.0 goes on from there. My old Italian mechanic, Carlo Durante at Alfa of Tacoma (RIP) and builder of many Alfa and exotic engines preferred the 2.5 for sound and balance. He felt there was a very small difference in the balance of the engine no matter how carefully he built the 3.0. Of course he sensed things that I would never detect. His GTV6 and Milano kept their 2.5 motors, liking that engine more than many/most exotic powerplants (and he drove all of them). So you can’t go wrong.
Interesting to read! Thanks! I'm not sure how much I would like the power benefit if it loses some of the "balance" or tone it has now. Even though I know the gtv6 is not fast by any means, revving the engine up and timing the shifts is so engaging that it feels fast and always puts a smile on the face. A little more speed of course wont hurt as while I'm doing all of this any modern day car driving next to me would wonder "what's with the smile when he's driving that slow". Anyhow I guess it is just a little more power would kick out the rear end a bit more easy as well. But the balance in the 2.5 is certainly something special. Pros and cons...
 

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Discussion Starter · #8 ·
If you choose to go with the 3.0 liter conversion do the round toothed timing belt mod as well. Alfa actually sells the parts to do the 3.0 liter engines (the right hand head is different on the Milano and later 3.0 liters than the 2.5s) so you can get the necessary sprockets and pulleys straight from the OEM. If you convert the 2.5 you'll have to get the kit from Chris Snowden Racing (CSR, alfettagtv6.co.uk) and it runs about 860 pound sterling = $1,122.91 at current rate of exchange
That's a good one Tom! I look into that. Thanks for the response
 

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I see! Is there anything you miss from the 2.5?
I would say that in addition to the slightly sweeter sound, There is a difference in the willingness to rev up vs more lower end torque for the 3 liter. My friend an I drove a 2.5 plus the 3.0 across Nevada and Utah, switching cars every couple of hours to get an immediate comparison. That’s basically what we came up with after pushing both cars hard.
 

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On the balance thing, that is a comment from a one-in-a-million genius, a 1960’s F1 mechanic that sensed things that “regular” great mechanics and drivers will never feel or sense. My brother has a 2.5 Milano with a Carlo-built stock component engine. It spins magically, essentially balanced/blueprinted in the right places, by a world class engine builder.
 

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1988 Alfa Romeo Milano Verde (grey,), 1988 Alfa Romeo Milano Verde (black) 1995 Alfa Romeo 164 ls.
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Though I have never owned a 2.5, I've owned four three liter cars. For the two valve? The ultimate sound is the 3.0l in combination with headers with a Stebro exhaust. Imho
 

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Though I have never owned a 2.5, I've owned four three liter cars. For the two valve? The ultimate sound is the 3.0l in combination with headers with a Stebro exhaust. Imho
This is a good point; much depends on what sort of exhaust you're able to run. For example, if you need to run cat's then you're behind the 8 ball on sound already. Running a non-cat system with some of those after-market 3-into-1 headers and a nice open resonator at the rear can sound awesome on a GTV6, every bit as good on a 3.0 as on a 2.5.

You say your car is a US market one with cat still in place. But do you need to run that in the Netherlands? When I put a 3.0 into my '85 GTV6 in Australia I sourced the engine from the US but used the original injection, which for pre-'86 cars in Australia meant no cat and no oxygen sensor. I actually used the 2.5 ECU which despite protestations is exactly the same Bosch part as the early euro 3.0 cars. I used some locally made 3-into-1 headers with the factory pipes through to the rear axle - but without the flexible parts - and a simple resonator at the rear (which my memory tells me was a generic truck part). The setup worked really well, the HP was exactly the same as a factory 3.0 75, it sounded great, and was not expensive.
 

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Discussion Starter · #14 ·
This is a good point; much depends on what sort of exhaust you're able to run. For example, if you need to run cat's then you're behind the 8 ball on sound already. Running a non-cat system with some of those after-market 3-into-1 headers and a nice open resonator at the rear can sound awesome on a GTV6, every bit as good on a 3.0 as on a 2.5.

You say your car is a US market one with cat still in place. But do you need to run that in the Netherlands? When I put a 3.0 into my '85 GTV6 in Australia I sourced the engine from the US but used the original injection, which for pre-'86 cars in Australia meant no cat and no oxygen sensor. I actually used the 2.5 ECU which despite protestations is exactly the same Bosch part as the early euro 3.0 cars. I used some locally made 3-into-1 headers with the factory pipes through to the rear axle - but without the flexible parts - and a simple resonator at the rear (which my memory tells me was a generic truck part). The setup worked really well, the HP was exactly the same as a factory 3.0 75, it sounded great, and was not expensive.
Thanks Aggie. Would you say there is a power increase with different manifolds, no cats and an open center as well? I read that the only real way to increase HP is to go with racing camshafts and that the exhaust and manifolds themselves don't really increase HP, correct?
 

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Discussion Starter · #15 ·
On the balance thing, that is a comment from a one-in-a-million genius, a 1960’s F1 mechanic that sensed things that “regular” great mechanics and drivers will never feel or sense. My brother has a 2.5 Milano with a Carlo-built stock component engine. It spins magically, essentially balanced/blueprinted in the right places, by a world class engine builder.
Thanks Peter, do you know what he changed on the 2.5 to get some increase of power?
 

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Thanks Aggie. Would you say there is a power increase with different manifolds, no cats and an open center as well? I read that the only real way to increase HP is to go with racing camshafts and that the exhaust and manifolds themselves don't really increase HP, correct?
It’s a long time ago now so I really can’t comment on that. I have a vague recollection that the headers did produce a little more power, but a more vivid memory is of a fiend who carefully cleaned up and enlarged in intake on an otherwise standard 2.5. That really did produce results, I can’t quote numbers but it was up there with some of the 3.0’s at club dyno days.
 

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Thanks Peter, do you know what he changed on the 2.5 to get some increase of power?
Ok - there is a difference between an engine that is built with skill and experience that is, with or without “special parts”, inherently smoother and “spins” exceptionally well. I am not an engine builder but watch and talk to some exceptional people. Rods selected or machined to match weights perfectly, parts selected or installed to optimal tolerances, small modifications and tricks, etc. New modern engines are built to very tight tolerances but old engines not as much. End result is an engine that revs more easily and smoothly. Think the inherent character of the 2.5, maximized.

Modifications for power are a separate topic.
 

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Discussion Starter · #18 ·
Hi All, thought I would give everyone an update on 2.5 vs 3.0

I will probably do a separate post on this as well where I'll keep everyone updated on the built.

2.5 was leaking more and more oil during my Schotland NC 500 tour. After going back to the garage where I purchased my GTV6 it was diagnosed there was a leaking crack shaft ring and pretty much all the other gaskets had to be done.

I was still a bit on the fence whether I would either do just the gaskets in the hope the rest was good, do a rebuild of the 2.5, or go ahead with the 3.0. Like many of you, my mechanics advised to go with the 3.0 liter since if you would ever do it, it was pretty much now. They had a few laying around so we could find a good candidate.

3.0 with verde pistons from a 75 (or Milano in US). The heads are from the mechanic himself from way back when and have larger air intake pistons which supposedly is good for better airflow and a few horses.

I have the option to work in the garage myself in my spare time to clean up the engine bay and retouch some sections that can use some sanding and a bit of paint to prevent from rust. If someone reading this is thinking of pulling the engine, try to put some time in and effort in the places you're not able to reach with the engine in (photo 8&9). These spots are particularly prone to collecting debris and water but are really hard to reach while the engine is in.

I'll keep people posted on this project. If there are any questions let me know! I'm really curious to see how this turns out. Thanks for all the feedback.
 

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