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Discussion Starter #1
Hi friends,

Thinking about getting a sweet 3.0 liter for my otherwise bone-stock, good running '86 GTV6.

My car runs great as is, but I'm always tantalized by a bit more torque and power. I've considered first trying out some hotter cams, but my mechanic (Alfa Italia in Burbank) seem skeptical that it will pass smog. Still, that could be an interesting step forward - has anyone ever done that to their 2.5 with good success? The other thing about my current motor is that there is a good deal of valvetrain noise that's always been there for the 6-7 years I've owned the car. Almost sounds like diesel clatter.

So as you can see I'm asking a few different questions here, but I guess what I'd like to know is: what would you do, if you were in my position?

Justin
 

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I have never swapped cams in a 2.5 but I have replaced a 2.5 with a 3.0 and then swapped cams in that motor. IMO the GTV6 should have received a 3.0 engine. It transforms the car. You need to go programmable engine management to get the best from big cams along with headers and a free flowing exhaust and that combination is unlikely to pass an emissions test.
 

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I've considered first trying out some hotter cams, but my mechanic (Alfa Italia in Burbank) seem skeptical that it will pass smog.
164 "S" cams or similar will pass smog without an issue but the power increase is subtle. You can feel a little bit better pull at the top end but it is certainly nothing like the power increase you get from a 2.5 > 3.0 swap.

Headers (with a good free flow Cat) will also certainly help, and shouldn't effect the actual smog test numbers negatively, but I don't know how they would fare with the visual inspection in California.
 

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Discussion Starter #4
I have never swapped cams in a 2.5 but I have replaced a 2.5 with a 3.0 and then swapped cams in that motor. IMO the GTV6 should have received a 3.0 engine. It transforms the car. You need to go programmable engine management to get the best from big cams along with headers and a free flowing exhaust and that combination is unlikely to pass an emissions test.
Makes sense, even though I'm not nearly as mechanically inclined as most of you folks here. Here in SoCal, most people that want something extra just do the swap, and frankly they don't seem to muck about with those other routes...presumably because of emissions.

164 "S" cams or similar will pass smog without an issue but the power increase is subtle. You can feel a little bit better pull at the top end but it is certainly nothing like the power increase you get from a 2.5 > 3.0 swap.

Headers (with a good free flow Cat) will also certainly help, and shouldn't effect the actual smog test numbers negatively, but I don't know how they would fare with the visual inspection in California.
Well, that's interesting! Thanks for the perspective. Going to corroborate with my mechanics (Alfa Italia in Burbank, CA) and get their take. They've been waiting for me to pull the trigger to see if Larry @ Alfa Parts Exchange or others has an engine for me, so I might just start down that road so I can look at some cost/benefit on this whole thing.
 

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Do the 3.0! So worth it.

Some thoughts on the matter, having done it myself:
If you are getting the 3.0 from a 164:
- the block is about 4mm shorter - you will need a spacer for the flywheel
- good time to get your injectors cleaned
- clean up plenum and valve covers and get them painted up (I did back crinkle - came up well IMHO)
- do some research on detensioners - I kept the oil fed one but refreshed with new seals etc - no leaks 5 years later
- while the engine is out look at the steering rack and engine mounts and freshen up. I overlooked the rack and wish I hadn't...
- Lighten the flywheel!!! Get it done by a shop
- Replace front guibo
- get the heads off the 3.0 and get them cleaned up if not already done - new valves, seats, seals, check clearances etc - good time to replace the cams if you are going to do that - you need to make sure you get new valve train gear (tappets etc) so you don't trash your new cams
- clean the crap out of the block but make sure you bolt down the cylinder sleeves so you don't break the lower seal - don't be tempted to rotate the motor!
- new timing belt (of course!)

Hope I'm not telling you how to suck eggs here...
Basically make use of the time the engine is out and apart.
Cheers
Marty
 

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A 164 engine requires some modification which has been detailed elsewhere but it has the advantage of much stronger rockers which are a weak point on the RWD motors.
 

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I would put S cams, California State approved headers, and 10 point compression pistons in your GTV6. The engine will still pass Smog and run better. I know that you will not pass the visual Smog inspection with a 3L engine and that is a big problem with engine exchanges.
 

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You have to know exactly where to look to distinguish between a 2.5 and a 3.0. Given the small number of these motors in circulation I would be surprised if a non expert would notice the difference.
S cams and pistons are likely to get you about 10 extra HP that you will barely notice. Been there, done that on a 3.0.
 

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I would put S cams, California State approved headers, and 10 point compression pistons in your GTV6. The engine will still pass Smog and run better. I know that you will not pass the visual Smog inspection with a 3L engine and that is a big problem with engine exchanges.
California State approved headers do not exist. Visual inspection? The guy is going to look for the 3.0 stamp on the back of the head!

S cams pass smog, are overpriced and make maybe 5 hp for a great deal of expense currently.
 

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Looks like I have a dissenting opinion. I built a "hot" 3.0 with RJR cams, Verde manifolds, Megasquirt etc. There is a big improvement in power, yes. But.... it is still not even close to modern sports car performance. If I were you, I would just fix what you have. Keep it stock. Lots of money spent for what ? If it is performance you are looking for , get a used Z06.
 

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I sold my 260 HP GTV6 and bought a 510 HP Jag XKR. The Jag is a great car but it is less practical and doesn't come close to sounding as good as the GTV6.
 

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California State approved headers do not exist. Visual inspection? The guy is going to look for the 3.0 stamp on the back of the head!

S cams pass smog, are overpriced and make maybe 5 hp for a great deal of expense currently.
Agreed that CARB-approved V6 headers do not exist. But, I do not think there are many smog techs who would know to look for a 3.0 stamp, especially in this day and age. Just make sure all of the year-appropriate smog stuff is in place and functional, vacuum hoses routed according to factory diagram for the model year of the car, factory or CARB-approved cat, ignition timing is set to factory specs, etc.
 

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Looks like I have a dissenting opinion. I built a "hot" 3.0 with RJR cams, Verde manifolds, Megasquirt etc. There is a big improvement in power, yes. But.... it is still not even close to modern sports car performance. If I were you, I would just fix what you have. Keep it stock. Lots of money spent for what ? If it is performance you are looking for , get a used Z06.
I kind of agree with this. I have a 2.5 with S cams, free flowing exhaust, and I can definitely feel it on the top end. But my VW GTI will blow the doors off it while using less gas, being more comfortable, and being likely an order of magnitude more durable.

IMHO, the point of these cars (and cars like, say, a Ferrari 308) is the total experience and not strictly performance. There's really no amount of modification you can do to make these cars perform like a modern sports car (or even sports sedan...). There will always be something most modern cars can do better. I think it's really about having adequate performance to keep up with traffic and have some fun (which is possible even in stock form), and having a smile on your face doing so. Modern cars are very antiseptic and homogenized, while a GTV6, or Milano, or even a Spider offer a feel that can't really be duplicated with anything else.

That being said, I too would love a 12 or 24 valve 3.0 in my car for a little extra grunt to help with merging on highways (and getting out of the way of idiots in NYC). Maybe one day I'll do it. But in the meantime, I'm still having a lot of fun.
 

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My goal was to have a GTV6 that was as fast as a contemporary 911. I got a lot of enjoyment from that plus being able to pull away from Miatas etc on track days.
 

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Agreed that CARB-approved V6 headers do not exist. But, I do not think there are many smog techs who would know to look for a 3.0 stamp, especially in this day and age. Just make sure all of the year-appropriate smog stuff is in place and functional, vacuum hoses routed according to factory diagram for the model year of the car, factory or CARB-approved cat, ignition timing is set to factory specs, etc.

I was joking about the smog tech looking for the 3.0 stamp.

You will run into the fact that when the smog tech in CA pulls up the static timing, they will use the 2.5 numbers.
 

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Discussion Starter #16
Mod the 2.5, swap to the 3.0, don't bother. Some very divergent opinions here, and they all make different sense. For someone who's not super mechanically skilled beyond oil changes, bulbs, and the occasional well-documented DIY, doing anything at all is pretty overwhelming. So, I'm a bit at a loss unless there's a clear path forward. Maybe not bothering with anything major is the way to go, unless I literally need a new motor at some point.
 

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Mod the 2.5, swap to the 3.0, don't bother. Some very divergent opinions here, and they all make different sense. For someone who's not super mechanically skilled beyond oil changes, bulbs, and the occasional well-documented DIY, doing anything at all is pretty overwhelming. So, I'm a bit at a loss unless there's a clear path forward. Maybe not bothering with anything major is the way to go, unless I literally need a new motor at some point.
I’m not surprised. There are varying views on this but globally the consensus seems to be the 3.0 conversion is a real goto mod for these cars.

I’ve owned both a 2.5 and a 3.0 GTV6, driven them daily as well as competed in them and a 24-valve 3.0. My 12-valve 3.0 conversion was a straight bolt for bolt swap of the 2.5 with a 3.0 164 core. I did it back in 1996, when it was still pretty rare and I even used the 2.5 injection system including the ECU. As I say, a complete bolt for bolt swap. In reality all I ended up using just the long motor from the 3.0, everything else was from the 2.5.

Anyway, I’d do it again in a heartbeat. It transforms the car, without changing its character.
 

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The 3.0 conversion is great for torque and drivability. The problem is the only legal way in California to do it is a Milano Verde swap and than get it CARB certified.

If you use a 164 motor, than they will want all the electronics from the Motronic system and a functional check engine light.

Most people do a swap and just never get it certified. Not really a problem, but the smog tech always pulls up the 2.5 static ignition timing. The dyno part of the smog is always the least of your worries.
 
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