Larger bore

[TeaBagger2006]

I know most people that do build either do a hone or bore the block .02 . I've seen .04 and have heard of much higher. Any opinions? If and when I do this to mine I want more displacement for my big single I'm gonna run . This sounds cheaper and easier than a striker kit. Blocks are cheap so worrying about being able to reuse a block is out of the picture.

 

[juddski88]

Mine is .040 over..plus a .0015 or so now to fix the mistakes of the last machinist. I wish I could give you a comparison to stock bore apples to apples but I cant. Just keep in mind that in order to really take advantage of the increased volume, youll want proper porting, especially with a big single. Hence the reason I no longer sport the socal stage 2 heads or the extreme cam. Im sure the cam could be degreed to work better for you but it wont be max-effort. And it'll cost too much to find out that it isn't what you thought it would be. I recomend giving David at DTS a call about it.

 

[TeaBagger2006]

bump, im thinking .060+ someone here has got to have more info. Tim, i dont think porting the heads would be cost effective for me but i will use aftermarket springs on the heads. i will be running a 4202r wit a .90 housing and a waste gate.

 

[LWATSON]

Interested in this also. I have an LB7 block that some moron left outside with the heads off. It has some rust scale on the parts fo the cylinders that were exposed and got wet. I can scrape it off with my knife and it doesn't look terrible but I'm pretty sure it needs to be bored. Just wondering how far I can go to try to save this block .040-.060 or more? I'm also planing to do just springs on my heads also.

 

[ecc_33]

Your wasting time and money. Just build the damn thing and run it!

 

[Diesel Technology Source]

I have 2 engines near completion using the larger bore .060. We also are using our new billet pistons with the new steel top ring and hard anodized for what should be a great alternative to what's currently on the open market for extreme power and reliability. However to the original poster why not get the benefits that the ported heads offer if you are increasing the bore size?

 

[Sledheadxp800r]

I've seen .130 overs for sale.

 

[Stingpuller]

Bore size

I have to ask one question. Has anyone used a bore gauge and checked the bore after you tighten the head studs down? I would guess not because not many have a torque plate. Now what do you think is going to happen when you make the bore thinner.

 

[Diesel Technology Source]

All engines when using increased strength fasteners for increased torque will pull the cylinder walls of even a stock bore. It is recommended to use a torque plate even on stock bore engines when using such fasteners. When decreasing the wall thickness by over bore any good builder will finish hone using a torque plate. You will immediately notice shading in the cylinder wall as the hone is passing over the voids.

 

[Stingpuller]

Bore

So your saying it doesn't matter with a thinner bore?

 

[jdlover1]

I had mine bored .040 over and filled halfway with blockcrete. That gt4202r should lite quick with a .9 housing. I had a 1.15 housing on mine and was overspeeding it. Went with a 1.32 housing and it still lites pretty good.

 

[Leadfoot]

So your saying it doesn't matter with a thinner bore?

That's not what I gathered from his statement.

I would take his statement to mean that even with a stock bore you will have the cylinder walls pulled so logic would dictate a thinner wall can/does pull more. In either scenario, proper machining (with a torque plate) is necessary. Obviously removing material makes the cylinder more prone to distortion.

And Jeff, I KNOW you are no idiot when it comes to engines (your past speaks for itself), so don't take these comments as aimed your way.

Some platforms have more meat than others and then there's a point where you have to weigh the pros/cons of block fill (to help stabilize SOME distortion) vs cooling (coolant and oil) and be honest with yourself about intended use.

I've even seen engines where all 8 cylinders were sleeved to create the maximum bore diameter (to the point where one sleeve is installed and then is slightly cut into when machining for the next sleeve) but also remain as rigid as possible, in classes where OEM blocks were mandated.

Most platforms have a "generally" accepted maximum overbore. After that sonic checking should be done. I believe the OP is asking what that "generally" accepted max is on a DMAX.


EDIT: Even stock fasteners distort cylinder walls so upgraded aftermarket fasteners tend to do it more. Many would be suprised to find out what happens to a SBC/BBC when properly honed with a deck plate then have the motor mounts bolted to it. Just bolting the motor mounts on can cause slight distortion (nevermind when the engine is under torque and pulling on them). I've seen my local machine shop bolt "dummy" mounts and even faux accessory brackets as well as heat the motor to simulate as close to real world conditions as they can. Obviously it costs more and for most street builds is not necessary. I know that's one reason for using motor plates as well.

 

[02ilduramax]

Does anyone know how big the duramax block have been bored over stock??

 

[ikeG]

Wagler is overboring their filled blocks .100

 

[02ilduramax]

Half fill or full fill?

 

[ikeG]

Full fill.

 

[ikeG]

Half fill or full fill?

If you're running coolant, probably not going to get any recommendations to overbore more than .040. Gets to be pretty thin cylinder walls. A pulling competitor of ours split a cylinder while running either .060 or .070, cant remember. I think half fill. He's a member on here but rarely posts. In reality, other than unshrouding the valves a little bit, your efforts could be spend better places in the motor. Even the gains from unshrouding them would next to impossible to measure.

The reason wagler and others go such big of a bore is to stuff huge valves in. They will run a 40mm valve when they do the 4.155 bore. Filled block is your only chance to keep it in one piece when boring out that far.

 

[Leadfoot]

If you're running coolant, probably not going to get any recommendations to overbore more than .040. Gets to be pretty thin cylinder walls. A pulling competitor of ours split a cylinder while running either .060 or .070, cant remember. I think half fill. He's a member on here but rarely posts. In reality, other than unshrouding the valves a little bit, your efforts could be spend better places in the motor. Even the gains from unshrouding them would next to impossible to measure.

The reason wagler and others go such big of a bore is to stuff huge valves in. They will run a 40mm valve when they do the 4.155 bore. Filled block is your only chance to keep it in one piece when boring out that far.

Also, unshrouding valves is a big plus on normally aspirated motors and can be money well spent, but don't see nearly as much benefit on forced induction motors. As 04jimc said, your money is better spent elsewhere.

 

[GSXRTURBO1]

bottom line is that if the cylinder doesn't stay round you are going to make less power no matter what the engine size is.

I would imagine bore distortion could occur in an unfilled block with as little as .060" overbore, especially if the fastener torque values are high enough.

As mentioned, a torque plate should be mandatory for any size overbore.

 

[Yellow Jacket]

Half fill or full fill?

Full fill at .100" over, ring packages become way more abundant at that bore I believe!

We are .060 over and full filled to minimize cylinder wall distortion with cylinder pressure.