V1 Oversized Pistons

[jirwin]

I'm toying with the idea of forged internals since its the only realistic upgrade path for me and my supercharged 2.2 LAP. There are two piston options - 86mm and 86.5mm. My understanding is that as the engine wears, the cylinder walls wear and lose shape. Due to this wear, people will have a machine shop bore the cylinders out a little bit (an extra .5mm in this case) to make them "true" again. Awesome.

So... is there a way to determine whether this is necessary without tearing down the engine? I'm leaning towards the 86.5mm because I figured I'd have/want to get the block decked/skimmed anyway. The engine has ~135K on it. Machining it guarantees fitment, while buying the stock 86mm size does not.

Thoughts?

 

[Gtstorey]

You will only know once the tear down is done and the bores are measured. The only thing I can think of that you might do before tear down is use a borescope camera to check the cylinder walls for scoring. I'm not sure if there are any downsides to just using the larger pistons other than you won't be able to do it again if this one fails. I don't know if there are any issues with thinning the sleeves that might cause problems.

You could probably pick up a 2.2 block for very little money. I would consider building a different block so the down time due to parts availability isn't a problem.

 

[jirwin]

You could probably pick up a 2.2 block for very little money. I would consider building a different block so the down time due to parts availability isn't a problem.

I've thought about that too. The block is cheap, so if it fails its easy to replace. I know parts availability is a little weird right now, but I'll have plenty of downtime here up north. Late October until April (if I'm lucky) it'll be too cold to drive. I'm also slightly concerned about sensors and other crap that comes with electronically managed cars. I've heard things about crank relearns and whatnot. I don't want to hassle with all of that if I can help it.

 

[Desert Sasqwatch]

With 135K on the clock there is little likelihood of just dropping new standard 86mm pistons into the cylinders. Almost a guarantee that one or more cylinders has worn to out of round and they will require the 0.5mm bore.

It is possible that an aggressive hone could bring cylinders back into spec, but that almost never happens with a high mileage motor.

As @Gtstorey indicated, to minimize downtime, picking up another 2.2 block is not too difficult, as they were used in most small and midsized GM vehicles. Best bet is to get one out of a wrecked vehicle, since the engine was likely running at the time.

 

[Gtstorey]

I've thought about that too. The block is cheap, so if it fails its easy to replace. I know parts availability is a little weird right now, but I'll have plenty of downtime here up north. Late October until April (if I'm lucky) it'll be too cold to drive. I'm also slightly concerned about sensors and other crap that comes with electronically managed cars. I've heard things about crank relearns and whatnot. I don't want to hassle with all of that if I can help it.

I would think a tear down to overbore would likely create the need to relearn sensors anyway. That will mean the block is stripped, bored and hot tanked. Of course if this was me, I would just build a pretty much new motor from an old block and replace sensors anyway.

 

[Ark :D]

I've thought about that too. The block is cheap, so if it fails its easy to replace. I know parts availability is a little weird right now, but I'll have plenty of downtime here up north. Late October until April (if I'm lucky) it'll be too cold to drive. I'm also slightly concerned about sensors and other crap that comes with electronically managed cars. I've heard things about crank relearns and whatnot. I don't want to hassle with all of that if I can help it.

No way.

 

[Dsteinhorst]

Are you thinking of switching to turbo after the build?

I could build mine, but my M62 is maxed out now, so another $1500 after the build to actually make more power isn't in the cards.

 

[jirwin]

Are you thinking of switching to turbo after the build?

I could build mine, but my M62 is maxed out now, so another $1500 after the build to actually make more power isn't in the cards.

Not sure yet tbh. I want to do it for more power, but also peace of mind that I can beat on it and the engine will take it. How do you know its maxed out?

 

[Gtstorey]

What pulleys are you running?

 

[jirwin]

What pulleys are you running?

3.1 for me and I believe 2.9 for him

 

[Gtstorey]

I don't know what the min size pulley you can run is, but the smaller the SC pulley the more boost you get. I don't know if changing the crank pulley to larger is an option on the ecotec. But assuming you are running stock crank pulley, you are not maxing out your SC.
LSJ Modular Pulleys – ZZPerformance

 

[jirwin]

Yeah my thoughts exactly. You can buy an oversized ATI crank pulley too. More power to be had with those mods and E85/Meth. More than the stock 2.2 internals can handle

 

[Ross]

Not sure yet tbh. I want to do it for more power, but also peace of mind that I can beat on it and the engine will take it. How do you know its maxed out?

Just before you hear a loud BANG, and oil flies everywhere, you were maxed out. If the engine isn't exploding, your not maxed.