420A what bore with std JE8.6:1 pistons (420a)

[99 gst 420a dsm]

what should the bore be in my engine block (420a) with standard 8.6:1 JE pistons? i herd it was .0045 over stock, i also herd not to go by what the JE instructions say, so i really need info from a someone with the same setup.... please let me know!!


mike

 

[Turbo 420a]

If they are standard sized 2.0 pistons then you don't need to bore at all. I've never heard of someone with a 2.0045 liter motor I haven't built my engine yet so I'm still kind of in the dark about internals - but I know you shouldn't have to bore for standard 2.0 liter sized pistons. Especially when they are rated at exactly 2.0 liters.

If you haven't purchased the pistons yet then you should consider getting larger (2.2-2.4) sized pistons so you can bore just to be sure there is no cylinder wall damage and get the extra torque the higher displacement provides.

 

[Kirby]

Slow down there turbo. The 2.2L and 2.4L motors are not what you think they are. If you are rebuilding your 2.0L motor then you can get standerd bore and not bore at all. Or you can order them .020 over bore and have the machiene shop bore the cilinder walls out .020 to match the pistons. I would not get the standerd bore pistons I would get the .020 overbore ones. That way you know you are starting out with true cilinder walls. The 2.2L motor is bored out but there are also crank and rod modifactions to get it to that displacement. If you tried to bore a 2.0L block to 2.4L then you would have no cilinder walls. The 2.4L motor is a completely different motor that uses different rods because it has a longer stroke from the factory. You can not get a 2.2L or a 2.4L out of a 2.0L by just boring the walls more. Pistons do not come in displacement sizes either, you can't just buy pistons to make your car a 2.4L. There are many things that make up a engines displacement.

 

[Turbo 420a]

Originally posted by Kirby
Slow down there turbo.

Umm, slow down? All I said above is he should consider buying the larger pistons instead of standard size so he could have the freshly bored out cylinder walls with no worries of previous cylinder wall imperfections. I didn't speak a thing of other rebuilding obstacles... Did I give some false information?

 

[Kirby]

Originally posted by Turbo 420a
If they are standard sized 2.0 pistons then you don't need to bore at all. I've never heard of someone with a 2.0045 liter motor I haven't built my engine yet so I'm still kind of in the dark about internals - but I know you shouldn't have to bore for standard 2.0 liter sized pistons. Especially when they are rated at exactly 2.0 liters.

If you haven't purchased the pistons yet then you should consider getting larger (2.2-2.4) sized pistons so you can bore just to be sure there is no cylinder wall damage and get the extra torque the higher displacement provides.

Well there are no 2.2L "sized" pistons nor 2.4L "sized" pistons. I was trying to say that the pistons alone do not determine the displacement of the motor. So above you say take advantage of the 2.2-2.4 sized pistons and get the benefit of the extra torque and HP. I just wanted to make sure you know that that's not how it works. For a 2.0L motor I could get .020 overbore, .045 over bore pistons but this does not give me a 2.2L or a 2.4L motor. Basicly to get a 2.4L motor you need to swap in a different engine block, and to get a 2.2L motor you would have to order from howell or make a stroker kit your self. So just getting .020 over bore pistons does not give me a 2.2L motor. Does that make sence? In your orignal statement it sounds like you think that just changing pistons will give you a 2,2L or a 2.4L motor and that is not correct. I did not mean to be harsh I just wanted to make sure you both understood that consept.

 

[workin_on_it]

ya the best way to do it is get pistons that are a bit oversized(.020) and have your machinist match them...that will give you the most accurate walls....and certain piston materials can run tight piston to wall clearances than others.
you could probably get away with standard bore pistons by just honing the walls, but like kirby said it is best to start fresh.
good luck with the rebuild

 

[Turbo 420a]

Originally posted by Kirby


Well there are no 2.2L "sized" pistons nor 2.4L "sized" pistons.

I didn't mean that the pistons were "sized" at 2.2 liters I was simply suggesting pistons sized for a 2.2 or 2.4 liter motor. And since the original question only mentioned pistons & bore, that was all I tried to mention also.

Sorry for miswording...

 

[Kirby]

But that is exactly what I am saying. There are no piston "sizes" for a 2.2L or a 2.4L motor. They are all the same size pistons. the reason those engines displace more is because of the stroke of the motor. All I'm trying to say is that the pistons do not change in a 2.2L or a 2.4L motor to make the higher displacement. For example, I could buy pistons for a 2.0L motor at .020 over size and buy pistons for a 2.4L at .020 oversize and the 2 pistons would be exactly the same. Does that make sence?

 

[Turbo 420a]

Originally posted by Kirby
But that is exactly what I am saying. There are no piston "sizes" for a 2.2L or a 2.4L motor. They are all the same size pistons. the reason those engines displace more is because of the stroke of the motor. All I'm trying to say is that the pistons do not change in a 2.2L or a 2.4L motor to make the higher displacement. For example, I could buy pistons for a 2.0L motor at .020 over size and buy pistons for a 2.4L at .020 oversize and the 2 pistons would be exactly the same. Does that make sence?

Yes. That does make sense now.

Thanks for clearing this up Kirby. I'm always learning