Low compression "Drop-in" pistons?

[autobot84]

I wanna go turbo and I'm looking for 400hp at like 18psi gtx3076r. 92 octane.

I'm thinking of a super budget semi build. Literally a piston swap for something forged in the realm of 9.5:1. A clean hone to scuff the inner cylinder walls and reassemble everything back to spec. Stock rods look up to snuff for the power I plan for. Bearings too. Upgraded valve springs will be called for, though.

Total cost in parts will be around $1000 doing all the work yourself.

The weak link to 300+HP pumgas are the pistons in this motor.

Has anybody tried or are doing purely "Drop-in" pistons?

For the people that say "why not just do everything since it is all apart?". Well, budget.

STi guys are known for Drop-in pistons...

[s2d4]

Are you sure the rods aren't the weak part?

[Travisty75]

Originally Posted by autobot84

I wanna go turbo and I'm looking for 400hp at like 18psi gtx3076r. 92 octane.

I'm thinking of a super budget semi build. Literally a piston swap for something forged in the realm of 9.5:1. A clean hone to scuff the inner cylinder walls and reassemble everything back to spec. Stock rods look up to snuff for the power I plan for. Bearings too. Upgraded valve springs will be called for, though.

Total cost in parts will be around $1000 doing all the work yourself.

The weak link to 300+HP pumgas are the pistons in this motor.

Has anybody tried or are doing purely "Drop-in" pistons?

For the people that say "why not just do everything since it is all apart?". Well, budget.

STi guys are known for Drop-in pistons...

Originally Posted by s2d4

Are you sure the rods aren't the weak part?

Yeah, every failure so far seems to have been rods turning in to spaghetti noodles and trying to say hi to the outside world.

[P&L Motorsports]

Originally Posted by autobot84

I wanna go turbo and I'm looking for 400hp at like 18psi gtx3076r. 92 octane.

I'm thinking of a super budget semi build. Literally a piston swap for something forged in the realm of 9.5:1. A clean hone to scuff the inner cylinder walls and reassemble everything back to spec. Stock rods look up to snuff for the power I plan for. Bearings too. Upgraded valve springs will be called for, though.

Total cost in parts will be around $1000 doing all the work yourself.

The weak link to 300+HP pumgas are the pistons in this motor.

Has anybody tried or are doing purely "Drop-in" pistons?

For the people that say "why not just do everything since it is all apart?". Well, budget.

STi guys are known for Drop-in pistons...

I think you may be misunderstanding the term "drop in pistons". Generally this term is used for other cars where you can simply remove the head(s) and literally drop the pistons into the shortblock. With a Subaru this is not possible due to the boxer design and frame rail clearances. The whole engine needs to come out. What you're proposing is an engine build with upgraded pistons.

Regardless, I don't recommend the "drop in" practice as it doesn't provide a proper way to set piston to wall clearance. Subaru engines are already notorious for oil consumption, and I would expect even more with an improper PTW clearance.

You're already going to be taking the shortblock out of the engine, it's just a bit more work to do a proper build to make sure everything is done right. A machine shop can bore and hone a block relatively inexpensively.

Ty @ P&L

[Dipstik-sportech]

It's the rods in this engine that r weak not the pistons

[cdrazic93]

Cheap.
Fast.
Reliable.

Pick two.

[malave7567]

Originally Posted by cdrazic93

Cheap.
Fast.
Reliable.

Pick two.

this has always been my favorite car-related quote.

and P&L hit it perfectly on the nail... this isn't an inline four/v-engine where you can change pistons with the engine never moving out the car. Not worth it to cheap out once you got the block out of the car, especially on a new car, IMO.

[wheelhaus]

Originally Posted by cdrazic93

Cheap.
Fast.
Reliable.

Pick two.

Similar to bicycle parts. Cheap, Light, Strong. Pick two.

There's a lot of things on a car that can be done on the cheap that are both fast and reliable, but none have anything to do with the engine. I also vote do a proper build, you'll thank yourself down the road. Just find a good reputable builder, preferably one with lots of happy Subaru customers.

[solus]

Everyday... More and more like the honda community

[Reaper]

@TopSpeed did this and I agree. The rods are fine for 400-500 it's the pistons that are fragile. It really only saves you about 1500$ to not do rods and hone it.

[ohnoitsthefuzz]

The fact is that your going to be shoving boost into an engine which was designed with pretty high compression. Dropping in pistons that lower the CR down to 9.5 as the OP mentioned would take a great deal of stress off of the rods but why chance it. If you're on a budget and want to make 2x+ the stock power with this motor and want it to be reliable, for long, thats not going to happen.

I would love my twin to have more power but can't because I don't have the funds at the moment to do it right. My opinion, hold off for a bit. If you're going to upgrade the pistons and valvetrain wait until you have the funds to pull the motor and do the bottom end properly. In the end, I have a feeling it is going to be much less of a headache, you'll be happier, and save yo' butt a lot of money.