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Discussion Starter #1 (Edited)
So earlier this year I did the 2.5 swap. I sold the car to my brother in law after owning it for 13 years and he blew the motor. I bought it back (unknowing that the engine was locked up), assessed, and decided it was time to make the leap.

The mods on the engine after the swap was:

2015 fusion 2.5 engine
Focus central cold air intake
Fusion 2.5 intake manifold w/ MSS throttle body adapter plate
MSS VCT delete
Crower stage 1 cams
Cosworth header and flex pipe
Cosworth balance shaft delete
Trubendz magnaflow 2.5" SS exhaust
MSS EGR delete
Tuned by Tom

So after lots of thought and research, I've decided to go to the boost side of life. With the 2.5, the engine is quite capable of handing some serious boost and a little goes a very long way. The stroke is actually a little shorter than that of the 2.3 and has a 9.7:1 CR. The miata guys are handling 400 hp at the wheels on the stock block but the rings are failing before the rods will. I will just be tossing 12-14 psi from the fswerks kit which should net me around 330 hp, but I'm still putting in molnar rods, new rod bearings, and ARP head studs. I am keeping the factory pistons because the CR is good enough for me.

While the engine is out I will be deleting the a/c. I bought an idler pulley to replace the a/c unit and a shorter belt. I'm also adding an exedy stage 1 clutch with flywheel and replacing the throw-out bearings. I also have svt front brakes I will be putting on. I've been setting that project aside, but nows a good time since everything else is getting done!

I'll try to update with pictures as I go along. Sometimes I forget to take them, but I'll try for those who are curious. And feel free to ask me questions and have me take pics.
 

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Discussion Starter #2
Today I pulled the engine. I had a bit of trouble getting the drivers side axle and couldn't get the slide hammer with crows foot on it until the engine was shifted with the hoist. Otherwise, here's some pictures. I didn't think to start taking them until after I got the car on stands and battery out.

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That's a good stopping point for now. Next I will get the transmission separated and engine on the stand so I can break it down. Lots of work to be done but I'm sure it will be worth it!
 

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Do you have to do a lot of modifications to get the engine in there? And do you know how much power you got out of it NA?
 

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Discussion Starter #4
Do you have to do a lot of modifications to get the engine in there? And do you know how much power you got out of it NA?
There were a handful of modifications to get the 2.5 in and running, but most of it was swapping over 2.3 parts like timing cover, sensors, crank pulley, flywheel, stuff like that. I did have to modify/fabricate the throttle linkage bracket to work with the factory throttle body and 2.5 intake manifold. That was pretty easy though. I can take detailed pictures for my setup if you need.

I never felt like the 2.5 was very powerful. Underwhelming is a good word. I checked timing several times, was tuned by focus-power, lots and lots of go-fast parts and never felt any better than the 2.3 in its prime and the 2.5 has just a little over 40,000 miles. One thing I did notice is the tailpipe would get black very quickly after I would clean it, but no smoke. I didn't notice it was consuming oil at a fast rate, but it was producing a good amount of blow-by in the intake manifold. Oil pressure was always on the high side between 60 and 80 psi, so I suspect the rings were leaking. I will do a leak down test before I tear anything apart, but will probably replace the rings and hone the cylinders regardless. Might as well while the engine is out and in pieces!
 

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Discussion Starter #7
The 2.5 stroke is much better then the 2.3 at almost 4 inch , What pistons you going with ?

Tom
I'm sticking with the factory fusion 2.5 pistons but using molnar rods with 20mm wrist pins. I don't think I can stretch my budget anymore for new pistons, but the factory ones are low enough compression so that should be good for the boost I'll be pushing.
 

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Discussion Starter #8
@euro-bred Was the wiring harness for the 2.5 plug-n-play with the 2.0 Duratech?
I'm using the harness that the car came with. Rhe factory harness. It's literally the same engine on the outside, so all you have to do is swap over all your sensors from the old engine to the new one and use your old harness. The hardest part about the swap is the a/c compressor getting in the way and getting the drivers axle out. Otherwise it's just time consuming.

Anyone who decides to do the swap needs to research, research, research, and ask lots of questions. Once it's done, you'll look back and chuckle about how simple it actually was.
 

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I'm using the harness that the car came with. Rhe factory harness. It's literally the same engine on the outside, so all you have to do is swap over all your sensors from the old engine to the new one and use your old harness. The hardest part about the swap is the a/c compressor getting in the way and getting the drivers axle out. Otherwise it's just time consuming.

Anyone who decides to do the swap needs to research, research, research, and ask lots of questions. Once it's done, you'll look back and chuckle about how simple it actually was.
Yeah I’m definitely following this thread lol, after my engine goes I wanna put a 2.5 in it. But in the mean time I wanna build one up since it’ll be outside of the car.
 

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Discussion Starter #10
Yeah I’m definitely following this thread lol, after my engine goes I wanna put a 2.5 in it. But in the mean time I wanna build one up since it’ll be outside of the car.
I did the swap back in March, so this time it's just an engine pull and build for me this time. I will do my best to document all necessary key points for a 2.5 swap such as the variable cam timing delete from massive speed system and all that includes, new intake cam gear, and correctly setting the timing and correctly tightening down the crankshaft bolt (harmonic balancer bolt), but I'll also go into stuff for a turbo build and turbo kit install.

Today I took the day off from the car. Tomorrow I will get the engine on the stand, timing cover removed, I'll clean up the ports and probably remove the cylinder head. I'm not going to remove the rods and pistons until I have the new rods and rings here, which might be a couple of weeks. I haven't ordered the rings yet! I will also go into the cylinder honing and remove any glazing that is there. One step at a time.
 

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@euro-bred I hear ya on the driver’s side axle!!

I found the best way to get it out is to get a ~2’ long piece of garage door cable, loop the ends, permanently crimp them down, and connect the crimped loops around a slide hammer. Tightly wrap the cable around the backside of the axle a couple times, pull the remaining cable taught while connected to the slide axle. The axle has always come out after 5-10 pulls with the slide hammer.

You’ll want to have someone hold the housing part of the axle that butts up to the transmission in order to avoid the axle teeth dragging across the seal as the axle comes out with all the hammer pulling. Replacing that seal is a pain in the butt.

I was looking for this little cable tool the other day. I seem to have misplaced it or I’d have included pictures of it with this post.

I can do a better job of explaining, with pictures too, if anyone is interested in how I did it and can’t envision what I described above. It may take me a few days ‘cause I’ll need to buy the materials and make another one.
 

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Discussion Starter #12
@euro-bred I hear ya on the driver’s side axle!!

I found the best way to get it out is to get a ~2’ long piece of garage door cable, loop the ends, permanently crimp them down, and connect the crimped loops around a slide hammer. Tightly wrap the cable around the backside of the axle a couple times, pull the remaining cable taught while connected to the slide axle. The axle has always come out after 5-10 pulls with the slide hammer.

You’ll want to have someone hold the housing part of the axle that butts up to the transmission in order to avoid the axle teeth dragging across the seal as the axle comes out with all the hammer pulling. Replacing that seal is a pain in the butt.

I was looking for this little cable tool the other day. I seem to have misplaced it or I’d have included pictures of it with this post.

I can do a better job of explaining, with pictures too, if anyone is interested in how I did it and can’t envision what I described above. It may take me a few days ‘cause I’ll need to buy the materials and make another one.
Glad I'm not the one lol. I always rent a slide hammer from the auto parts store and the fwd "crows foot" attachment. I never have a problem with getting it in there but this time I really struggled with it! I'm just going to not think about the possibility of a damaged output seal and cross that bridge when I come to it lol.
 

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I'm sticking with the factory fusion 2.5 pistons but using molnar rods with 20mm wrist pins. I don't think I can stretch my budget anymore for new pistons, but the factory ones are low enough compression so that should be good for the boost I'll be pushing.
Then leave the stock rods as well , would be a waste to use the cast stock pistons , also need to add ARP head studs to the list

Tom
 

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Discussion Starter #14
Then leave the stock rods as well , would be a waste to use the cast stock pistons , also need to add ARP head studs to the list

Tom
Why would it be a waste to use stock cast pistons? I'm looking for reliability, not chasing high numbers. I wish I could add pistons to the list but they aren't a weak point and offer a decent low compression ratio, so the benefit outweighs the gain I'd get. The rings are weaker, so I'm replacing them.

ARP head studs should be here today along with a new head gasket and the crank pulley bolt.
 

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Why would it be a waste to use stock cast pistons? I'm looking for reliability, not chasing high numbers.
Because the stock Pistons are Cast , why change the rods if your not changing the pistons , there both as weak as the others

Tom
 

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Discussion Starter #16
Because the stock Pistons are Cast , why change the rods if your not changing the pistons , there both as weak as the others

Tom
My information is coming from Joe at dynotronics from the miata forum. The they seem to have the most information and R&D time with the 2.5 and they say the rings are the weakest point followed by the rods at the wrist pin near about 420 hp. Considering I will be about 100 hp and 6-8 psi shy from the limit of the stock rods, and the fact that nobody has noted having issues with the factory pistons, I should be okay with saving ~$600 and "risk" using the stock piston heads lol. The molnar rods are cheap insurance since I'll be around 320 hp and I'm just wanting it to be reliable and fun to drive.

Don't get me wrong, I do appreciate the concern, I simply haven't heard from anyone having problems with the factory piston heads. Especially with only running 12-14 psi. That's relatively low boost for what the 2.5 is capable of.
 

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Discussion Starter #17
Made my own flywheel locking tool for those stubborn flywheel bolts and crankshaft bolt. Made this back in March.
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Got some goodies in today. The belt is shorter than the standard belt because I'm deleting the a/c. Also got the pulley to go with it. Piston rings are also here but not pictured. The rods will be here next week.
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And here's a good picture for those who want to know the best place to drill through the firewall to run stuff for your wideband, or any other gauges. It's the best place I could find, anyway. Just be careful to plan out the exact location because you can get really close to where the gas pedal mounts on the inside.
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There won't be much progress over the weekend. Monday I should start tearing down the engine and cleaning up the flanges and ports.
 

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Discussion Starter #18
Tomorrow starts the engine tear down! Going to get it on the stand and get the valve cover, oil pan, and timing cover off. I hope to take the cylinder head off along with the rods and pistons. I will measure the bore and start gapping the piston rings. I think I'm going to go with 0.018" for the top and 0.020" for the second ring, but I'll take that leap when I get there. They are just regular Mahle rings, but since this will be a turbo application I figure I still better gap them for boost. The rods should be here this week and hopefully I'll be done with the rings, but that's a tedious process.

I also started fabbing up an oil catch can for the pcv. I don't want to risk carbon build up on the valves so I'll just run a simple catch can. I'm making it out of 1/8" aluminum plate. Very simple design.

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On the top I will put a flange and thread it for 6 bolts and just RTV it shut to seal. I will have a drain plug at the bottom and compression fittings on the side with clear tubing for a sight-glass. I haven't figured out how I'll have the plumbing set up for the top plate, but I think I want to route it back into my intake manifold... Buuuut I'm not sure yet. I might just have it vent into the atmosphere.
 

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Cut the bottom of the pcv to remove spring and plunger , Put a hose on it and run it over and down to the trans and let it breath . you dont want it hooked to the intake at all even with a catch can

Tom
 

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Discussion Starter #20
Cut the bottom of the pcv to remove spring and plunger , Put a hose on it and run it over and down to the trans and let it breath . you dont want it hooked to the intake at all even with a catch can

Tom
Yeah, I kept thinking about that and I figured it would probably be better to not have the pressurized intake hooked up to the non pressurized crankcase.
 
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