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Old 12-29-2020, 05:17 PM   #5
Scooby Specialist
Member#: 30804
Join Date: Dec 2002
Chapter/Region: SWIC
87 Yugo


Originally Posted by undyjr View Post
As I have some gift cards burning a hole in my wallet I'm looking forward to the next phase of my build. This is where I'm at with my 2019 STi:

Blouch 20G XTR
Injector Dynamics ID1300s
Cobb Big SF intake with air box
Cobb 3 port EBCS
Cobb LF bypass valve
Cobb flex fuel kit
Grimmspeed TMIC
Grimmspeed catted downpipe
Grimmspeed EWG up pipe
Turbosmart 38mm EWG
Killer Bee holy header

380WHP and 370WTQ on a Dyno Jet

My plan is to pull the motor, delete the air pump, split the case, replace the rods and pistons, and install the motor with a new ACT clutch with streetlite flywheel. My tuner gave me a conservative tune because of the factory shortblock. Is 450-500WHP attainable on a Dyno Jet? I plan on using Manley forged rods and performance platinum series 99.75mm pistons. I will have the machine shop size the bores and gap the rings. Since the car is a DD and lives on E85 should I go with 9.8:1 or stick with 8.5:1?

Do I need to replace the rod bearings? The motor has 30K on it and my past 4 oil analyses have been perfect. It's tempting to replace EVERYTHING but I don't mind saving money where I can. Although I have a feeling y'all are going to tell me to replace the main bearings too. It goes without saying that I would install the OEM bearings back into their original position. Are ARP head studs a necessity? I foresee a retune approaching 25#s of boost. This is just the next step in my build and I strangely look forward to pulling the motor myself. Anyone local to the Hampton Roads aka Coastal Virginia area that wouldn't mind renting me some Company 23 tools feel free to pm me
Lets take a step back here please, and talk about a few things.

1) From a technical standpoint the factory rod and main bearings are perfectly fine. From a cost standpoint the winner is to go aftermarket which is why you see the change. The argument that a softer bearing will save your crank if a bearing fails is BS. Complete BS. Hard or soft if you kill a bearing the crank will be scored. A BNIB crank from Subaru is under $400. You'll spend that getting a worn crank ground and polished. Bottom line, Subaru cranks are disposable, and honestly for the price one hell of a bargain for what you get.

2) The way your post reads is that you're going to open the case, swap your old rod bearing onto new rods, put it back together, and slap some pistons into the holes. DO NOT DO THIS!! You will be in for a world of hurt.

I have said it before and I will say it again. A Subaru case is a floppy bag of aluminum that just holds the guts in. You've cycled this motor a number of times now, and you will need machine work to make everything straight and true. By jamming new stuff into a used case you're going to be very disappointed. By jamming your old rod bearings into new rods (even if they were factory Subaru rods) you're going to be very disappointed.

Now, if you've got the money, and the time, and are willing to risk a failure all for the sake of a learning experience then by all means give it a shot. If you're like the rest of us poor schlubs, and you want to do it right then do it right and don't take shortcuts.

Quite honestly, if you're not made of money and free time you will be VERY well ahead of the game to purchase a shortblock. Some (but certainly not an all inclusive list) of places I would go are:

TiC <- I'm partial to these, but I'm a bit biased.

My number one, never ever go there, why the F they are still in business, you'll hate life, your car, your dog, and your significant other place is GCH. Do NOT make that mistake.

Now, also along the lines of floppy aluminum please do not ignore you heads. Have someone who knows what they are doing check those over, and deck them at the very least. A proper deck. Using a proper machine. Set up to properly cut aluminum. Not Billy Bob and his Buddy with a whiz wheel on a grinder or old Smokey MaGee and his 1964 surfacer that's set up to cut old Ford cast iron heads using a graphite gasket.
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