Utinator

I know, I know....use the search feature. Well I did, and I didn't see anything on the max bore for an aluminum gen-4 block. With the aluminum gen-3 blocks, it was generally accepted that .007 was about the max you could go without the sleeves getting too thin. There are plenty of threads on bored-out iron blocks, but I'm only interested in aluminum blocks. What is the most the aluminum gen-4 blocks can be bored/honed?

If cost and availability were no issue, then I'm sure we could all agree that the only option would be the 6.2 block. Since the 6.2s cost much more, the 5.3 and 6.0 blocks are more appealing. So, what's the biggest bore you have heard of from the aluminum 5.3 and 6.0 blocks?

Che70velle

iTrader: (6)

I have personally taken an aluminum Gen4 6 liter block out to 4.030”
I can’t comment on the aluminum 5.3 blocks, as I’ve never had one bored.
Consult your machinist obviously about overbore. They should sonic check the cylinders before setup in the boring machine to ensure there is enough wall to do what you want. Of course you can always have the block sleeved. It’s not a very expensive process, all things considered.

Utinator

Thank you for sharing your first hand experience. I was thinking .020" would be pushing the limits. It's nice to know they might be able to go .030" over. An aluminum 396 or 408 CID would be awesome.

I was just curious about the over-bore sizes, because I thought it would be cool to build a 392, 396, or 400 CID LS motor. It doesn't look like a 400 CID would be possible with an aluminum block. That's ok though. That extra .030" leaves a lot of fun options on the table.

Mavn

iTrader: (3)

4.060 on an aluminum ls2 block 4 years ago still running n/a to this day inna trailblazer

99 Black Bird T/A

iTrader: (4)

I've heard of quiet a few of those. Do you think realistically going .005 more for .065 over on an LS2 block is doable? One could use a stock LS3 piston etc.

grinder11

iTrader: (1)

Using the stock piston would be the only reason to worry about .005" bigger. You'd never feel it sotp. If you're going to try for a 4.065" bore, I'd have it sonic checked. Maybe someone more LS2 specific knowledgeable will chime in.......

Corona

👍 you should always do that. Best person to ask would be as we all know Steve @ RED.


Every block or sleeve is different reason for sonic testing

Utinator

I have been wanting to start with an L76 long block. I didn't think it would be possible to get that close to a 6.2L. Of course, a sonic check would be necessary before any boring.

My neighbor has an LC9 short block that I plan to help him build for his truck. The cylinders are rusty from sitting, so it will need machine work before building. It would be awesome if it could be bored out to a 3.898" like the iron blocks. I suppose we will need to find a place that can sonic check the block first.

Mavn

iTrader: (3)

I've seen plenty of 4" bore aluminum 5.3s. Chris 1313 builds them

Utinator

Is that just bored out, or with new sleeves? There's a big price difference between the two.

gnx7

iTrader: (28)

If it were new sleeves I have an alum 5.3 with a 4.190" bore

My buddy has built many alum 6.2's with 4.075" overbore and no issues

Mavn

iTrader: (3)

Bored out

Utinator

Why is every one not doing that? If that's possible and reliable, then every LC9 should be at least a 5.7L. I will definitely be looking into this.

Utinator

That's only .010", so that's not surprising. If it could go out to a 4.125", that would be impressive. Those blocks cost way more than the others. The oversized piston options are more limited too. The bored out 5.3L or 6.0L is just more cost efficient.

99 Black Bird T/A

iTrader: (4)

FWIW have read of a couple of LS3 blocks going to 4.10 but didn't see any follow up or details. Got impression it's not every block that can go that far due manufacturering variances.

Mavn

iTrader: (3)

I've personally seen a 4.100 ls3 . Running in a c5. Not sure if it lasted or what . Just know it was running and running gooood with ls7 heads lol

Corona

A bad tune is what generally ends a over bored factory sleeve.

grinder11

iTrader: (1)

Exactly Still, the thinner you go on the sleeves, the more critical everything else becomes. I've personally never heard of an LS3 going to a 4.100 bore. I'm sure it has been done, but how thin the sleeves become in even the very best blocks, would certainly become a huge question mark. I'd also have concerns as to how much wear capability is left. In other words, if you did somehow score a cylinder, would you break through the sleeve, and into the aluminum, if it was deep enough? IDK......

99 Black Bird T/A

iTrader: (4)

Can you share any specifics or examples?

Thanks

Corona

boosted app long time ago read... reason to alway sonic test Any block if your going with Minimum Maximum boring. Thrust side is the most problematic.

Sorry BB T/A about not answering...notifications are set on off or it doesn't show as a notification..most I've heard of a ls3 going over bored is .080

Crazy thing about trying to Max a bore? A person like myself doing something crazy as this is only worth 10 fwhp if that and you'd lose reliability with the sleeve being thinker. At this point may as well resleeve the block then its lost its appeal with a cheap starting point being a typical ls3 block just wanting to be stroked or 376 cubes and 650 hp.