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01' RS BRP
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42 Posts
Discussion Starter #1 (Edited)
After much reading and searching for the aftermarket support I am close to starting a 251 SOHC build.

Current Plans:

Basically a Delta built head.
-2000 cams
-flat nitrided valves
-a good p&p
-AVCS springs/retainers/keepers

Block:
-10.5:1 Wiseco slugs
-Stock rods, maybe eagles.
-King bearings
-Normal shortblock machine work

Other:
-OBX EL headers/Resonator/tsudo the rest of the way.
-Ported, cleaned up intake manifold.
-Port matching

For what it's worth I'm running a 4.44FD DCCD 5pd RA trans and STI suspension w/ coilovers.

Looking for a decent torque increase but still have a decently reliable DD. I'm focusing more on removing rotating mass and pulling weight off the chasis, not necessarily dumping ponies into the motor. Suspension will also be getting some major attention soon as well. Any thoughts on the above plans?

My questions pertain to knock and engine management/reflash.
What did you guys for the reflash/management?
As far as knock, a local shop told me the geometry of these motors causes excessive knock when built up. Any of you have bad issues with this?

Thanks fellas
 

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01' RS BRP
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42 Posts
Discussion Starter #3
It's a 2001. That ad is what got me thinking about re-flash over a full on engine management.

Thinking about a lightweight flywheel and aluminum driveshaft too, forgot to mention that!
 

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95/99 Brighton STi
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Agreed with lightweight flywheel, crank pulley and either aluminum or CF driveshaft. A good set of lightweight, forged wheels will help a lot too. I've got a set of 16" BBS wheels that weigh 14 lbs each! (For sale btw)

Have you driven on the RA trans yet? You'll love it if you haven't. I love mine.
 

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2001 Impreza RS - Black
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227 Posts
I'd say to go up to 11.5 compression with STI rods. That's perfectly safe on 91 octane. And then you might as well go slightly oversized on the pistons as well.

The Delicious reflash is an easy route for the EM.

As for knock, an aluminum radiator and oil cooler will help with that.

From what I've read, the aluminum driveshafts need a little 'massaging' of the drive shaft tunnel to provide the proper clearance because they're a larger OD, while the carbon drive shafts are the same OD, so they just bolt right up.
 

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01' RS BRP
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42 Posts
Discussion Starter #6
Agreed with lightweight flywheel, crank pulley and either aluminum or CF driveshaft. A good set of lightweight, forged wheels will help a lot too. I've got a set of 16" BBS wheels that weigh 14 lbs each! (For sale btw)

Have you driven on the RA trans yet? You'll love it if you haven't. I love mine.
I have! Been ripping it for about two years and will never use another type of trans! This thing makes small horsepower incredibly fun.

Ah man the 16's won't clear the brembos or I'd be all over it!

I'd say to go up to 11.5 compression with STI rods. That's perfectly safe on 91 octane. And then you might as well go slightly oversized on the pistons as well.

The Delicious reflash is an easy route for the EM.

As for knock, an aluminum radiator and oil cooler will help with that.

From what I've read, the aluminum driveshafts need a little 'massaging' of the drive shaft tunnel to provide the proper clearance because they're a larger OD, while the carbon drive shafts are the same OD, so they just bolt right up.
From what I've read if I were to put the RS high comp pistons on the STI rods the wrist pin location on each will put the piston in the wrong spot, as in it will hit the head? That's a cheaper route and I am definitely open to that setup.

Thanks for the suggestions fellas!
 

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2001 Impreza RS - Black
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227 Posts
Yeah, the RS rods and STI rods are different lengths. However, if you're getting custom pistons, they can make the pistons match whatever rod length you want. Or TWE has on the shelf (if they're in stock) 11.2:1 compression pistons for the SOHC EJs that are made to be used with the STI rods. They're made by Wiseco. Wiseco also has pretty reasonable prices for customs pistons.

You guys make that RA trans and 4.44 fd sound pretty sweet. I've been thinking about moving in that direction, or at least an LGT/OBXT/FXT trans with the 4.44 fd.
 

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01' RS BRP
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42 Posts
Discussion Starter #8
I'm digging this hybrid EJ business. What about EJ255 Crank, rods and custom 11/2 pistons? seems strong enough and not as costly as all forged stuff, with isn't necessary in this fairly mild build. Using the numbers from a quick search I get: 251 rod length 131.6mm and 255 rod length at 130.479mm. I haven't taken into account the crank difference, which seems to be elusive info on the interwebs.

The RA rocks. You don't need to stack tons of horsepower on to have lots of fun. Only drawback: 60mph on the highway is 3000rpm and goes up quickly from there!
 
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