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Nov. 12, 2011 11:56 a.m. Ksean6969 None

I have a 2004 Subaru Impreza 2.5RS with 121,000 miles on it. It was my daily drive for 6 years and now gets used during the winter. I don't abuse my cars, so i figure in another 4 to 5 years my Impreza will have a well earned 200,000 on the power train. I'll be replacing it with a newer Impreza for daily use. I was thinking of making a clean street driven vehicle to autocross, track day and just whip around on the highway. All of this on an a reasonable budget. I have the suspension & wheels sorted out, keeping it simple. Now there is the engine. That's where I'm uncertain and unclear. I'm staying naturally aspirated by choice because i just want a fun car that won't be complicated to repair when something malfunctions. Aside from intake, headers and exhaust, I'll have a lot of miles on the engine. I want to maximize the performance of a simple engine. I thought just rebuild the block with stock components and focus on porting polishing the head for better flow and breathing. This would give me a reliable engine that breaths better and maybe improve the power output slightly. Am I heading in the right direction?

Thanks, Kwame Ksean6969@aol.com
Nov. 12, 2011 1:09 p.m. ValuePack Dork

Sounds like you're on the right track. The EJ251 will never be much of a powerhouse normally aspirated, but I'd suggest a pair of mild Delta cams for your list. Fairly inexpensive, and will pep the car up a bit without sacrificing reliability or driveability..
Nov. 12, 2011 1:23 p.m. mad_machine SuperDork

I know you said you didn't want to Turbo it.. but I do seem to recall that there was once a Supercharger kit for that engine. I think Subie bringing the WRX out put paid to it.. but there might be a few floating about
Nov. 12, 2011 6:58 p.m. ddavidv SuperDork

I discourage people from boosting the 2.5. The standard compression ratio is pretty high (9.5:1 or thereabouts) and they are already known for head gasket failures. Doesn't mean it can't be done, but the OP doesn't want to go that route and I support him.

Provided you're willing to accept a horsepower limit below that of a WRX there's nothing wrong with a 2.5 Impreza. Spend your money wisely on the suspension and maybe a little bit better brakes (no need for Sti level stuff). The problem with the engine is a rebuild and/or internal parts are going to be very expensive. A low mileage junkyard engine will cost far less, and since these go 200,000 easy I wouldn't worry about just swapping it out. The problem with trying to build a n/a engine is the cost per modification is extremely high for the HP increase you wind up with. You've got to really love the car and want to keep it forever for that to make sense. This is coming from a guy who built an Audi engine that wound up being as much as the entire car was worth. That was a fun project, but a bad monetary decision when I decided I wanted to go faster/different car. I wish I'd had the money to put into the next car instead of watching that expensive engine drive off with someone who didn't have a clue.