So I log on to my local board to see someone selling a 2.5L Talon motor. I was curious as to what the story was so I bring up the ad and start reading the details.

It's a 6 bolt G4CS block, your typicl 2.4L motor (86.5mm bore x 100mm stroke), but says it has .040 pistons. So that works out to a 87.5x100 which yields a displacement of 2405.6cc.

Am I missing something here? Since when did 2406cc = 2.5L?

Because, the bore on the motor is 89mm, not 87.5
which works out to 2489cc.
So, perhaps its not exactly a 2.5 but thats far closer then 2406

Close enough.... 2.5L in my books.

Where does 89mm come from?

Block is 86.5mm
Pistions are 1mm over as stated

Should yield 87.5mm bore or 2406cc

I never did any measurements myself with the motor, but the pistons picked up were .040
Headgasket was for an 89mm bore.

No problems from Mississauga Engines on any of the parts I had, and they would have told me an issue had there been one.

The block is bored to match the pistons, not the headgasket. So as I said above, the motor is 2406cc.

okay, so lets say the block is bored out to match the pistons, because of course this is its done, im not arguing that by all means
But, what would happen if you use a headgasket 2mm over sized?

I'm not 100% sure what would happen. You have a small gap there that isn't ideally supposed to be there, but it is so small it might be negligable.

Wow Pistons are .40 oversized? Check the block if its over its machining limit.

^^^^ LMAO

Stock bore on a 2.4 is 88mm. 1mm oversize makes it 89mm, and 2489cc.

That's why a 2.4 crank in a 2.0 block makes a 2.3

Nick, where do you come up with 88mm for the bore?

4g63:

Bore - 85mm
Stroke - 88mm
Displacement - 1998cc

4g64:

Bore - 86.5mm
Stroke - 100mm
Displacement - 2351cc

With your comment of 2.4 crank and 2.0 block:

Bore - 85mm
Stroke - 100mm
Displacement - 2270cc

Of course those are all assuming std size.