.040 Over bore too much?

smh0101 · Post by **smh0101** » Thu Jun 12, 2008 11:33 pm

For my 2.35 I have to use .020 over bore pistons, thus I have to have it bored...

Now what I was thinking, why not go with .040 over bore and make the engine a 2.4L closed deck.

What do you guys think?

SubaruNation · Post by **SubaruNation** » Thu Jun 12, 2008 11:43 pm

smh0101 · Post by **smh0101** » Thu Jun 12, 2008 11:46 pm

The thing I'm concerned it boring too much.

ChesterKV · Post by **ChesterKV** » Thu Jun 12, 2008 11:47 pm

smh0101 wrote:For my 2.35 I have to use .020 over bore pistons, thus I have to have it bored...

Now what I was thinking, why not go with .040 over bore and make the engine a 2.4L closed deck.

What do you guys think?

Sounds good to me except I believe Subaru factory says to not overbore beyond 0.020 inches. They're being conservative, of course. Also, check with your piston supplier and make sure they offer an oversize of 0.04...... I don't think all of them do. At 0.04 overbore I would definitely go with molybdenum coated skirts to reduce heat/stress as much as possible on the cylinder bores. It should be fine then.......... at least that's the theory.

What's your final setup going to be ?

.

smh0101 · Post by **smh0101** » Thu Jun 12, 2008 11:53 pm

Wiseco, they make them for this build.

And its gonna be:

22t block
2.5L Phase 1 Crank/Rods
RS 2.5L DOHC NA Heads
vf39 or td05-16g
ej20g intake manifold
stock new subaru bearings
wiseco pistons
sti 565cc injectors

555BCTurbo · Post by **555BCTurbo** » Fri Jun 13, 2008 3:29 am

You could probably get away with it...but .040 is a big cut...and will pretty much render your block useless for future boring. Keep in mind that it is really double the necessary clean-up bore...which is why Wiseco makes those pistons in .020.

Have you done the math to find that twenty thousandths more per hole will actually increase the displacement by 1/20th of a liter?!?

PhyrraM · Post by **PhyrraM** » Fri Jun 13, 2008 4:18 am

Nick beat me to it.

You will never notice (seat of pants) that extra displacement.

Being able to clean up the block again should you have a meltdown is far more valuable.

If your looking for a DynoQueen, by all means bore it out.

smh0101 · Post by **smh0101** » Fri Jun 13, 2008 4:22 am

haha, no. I want drivability, screw dynos!

Mmkay, sticking with .020!

93forestpearl · Post by **93forestpearl** » Fri Jun 13, 2008 8:17 am

I was in the same boat. I chose the .020 overbore for the fact that I can always take it out a little more if the need arised. Its not worth the .04 liters. Plain and simple.

If you want to get serious like that send your block to Darton. They'll hook you up with a 2.65L. Or Ron at what used to be Axis.

AWD_addict · Post by **AWD_addict** » Mon Jun 16, 2008 7:01 am

Does your block have damage to the cylinder walls? I have a block that had damage in #4. The machinist said .020 over would clean it up, but it did not. Rather than get it sleeved to accommodate .040 over pistons, I just got another block that had nice walls.

Just something to consider.

GodSquadMandrake · Post by **GodSquadMandrake** » Sun Jun 29, 2008 6:18 am

I overbored mine .040" and there was plenty of room on the cylinder walls left.

AWD_addict · Post by **AWD_addict** » Wed Jul 02, 2008 7:23 am

Good to know.

BAC5.2 · Post by **BAC5.2** » Wed Jul 02, 2008 12:30 pm

Stock overbore allowance is .050

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.040 Over bore too much?

.040 Over bore too much?

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