Can someone explain exactly what a stroked engine is and a bored engine and the main differences between the two.

I see videos on YouTube of c6 z06's with a stroked 440 or a stroked 454 and I'm curious exactly what it is. Is it the same original LS7 block that comes in the z06 but there is a change to the crankshaft and pistons to make it larger displacement? It's not an all new block is it?

What is the cost of something like that? And how much more power does it typically add?

For example if you take a stock LS7 (505hp and 480tq) and "stroked" it to a 440 or 454 what would the numbers look like then?

Is doing this worth the money?

 

In simplest terms, both “boring” & “stroking” an engine are means to increase displacement, that is to create a larger volume within each cylinder to allow a larger volume of fuel & air to be compressed & ignited, thus leading to greater power from the engine. “Boring” is the process of increasing the inside diameter of each piston bore & installing the appropriate larger diameter pistons to fit the larger bore. “Stroking” is the process of installing a modified crankshaft with longer “throws” which in turn increases the stroke of each piston (the up & down motion) in the cylinder bore, again increasing the volume of the air/fuel mixture in each cylinder. Typically, new connecting rods are needed for a “stroked” engine. There are mechanical limits to how much additional displacement can be achieved with each process, so often an engine is both “bored” & “stroked” to gain maximum displacement increase. Hard to say what HP gains would be since so many factors are involved, but typically it would be fairly substantial, especially since other mods (i.e. intake; exhaust; tune; etc) are usually done concurrently. Cost is very subjective depending upon how much work is done, but several thousand $$$ is to be expected. Is it worth it....for the street I would say NO, but for serious competition, definitely YES.

 

Thanks for the reply. I already have full bolt-ons, still running on the stock cam though. I want to keep this car N/A so if it would yield a fair amount of power gains then to me it would be worth it....depending on the cost of course. Can you stroke the stock LS7 or do you need to buy an aftermarket block in order to do this? A quick search online shows 440 stroker kits going for around $2500 or so. I'm sure labor to install the kit would be close to if not more than the kit itself.

 

Is there not a proportional difference in hp/tq in doing bore vs stroke?

If a change in an 6.3 liter ls3 to a 383 by bore, there is a greater increase in hp vs tq where by stroke has a greater increase in tq vs hp.

 

Traditionally it seems increasing the stroke increases the torque in the lower RPM ranges vs increasing the bore. So low end torque stroke > bore.

However, the trade-off of stroking is increased piston speed; which equals greater stress on the pistons/rods/crank. This limits the safe upper RPM range. All bore motors can usually be spun higher, with less stress, and since HP is a function of torque with respect to RPM; max HP bore > stroke.

Yes there are probably thousands of variables that can flip which motor makes more low end torque or max HP, but in general...

With a LS7 just do a cam swap, it's way cheaper, simpler, and you can get huge gains. Heck GM gave you a forged crank and titanium rods to help the motor survive to it's 7K red line; and a completely different block to reliably handle it's 4 inch stroke.

 

Typically heads/intake manifold limit top end power, and doing a 440/454 just adds some low end torque.

Longer stroke has potential downsides for piston wear, bearings, etc.

It is easy enough to make 600+rwhp NA on a stock bottom end. The $4-5k+ to add a few cubes, just for more low end isn't the best way to spend money.

 

Depends on what you want

Bored= cylinder is larger in diamter doesnt really add much
Stroke=piston goes farther up and down for ea crank revolution

if comparing power gain for either stroke wins.
If i had a dime for every motor I went nuts trying different cams intakes looking for "it" Id be rich. Increasing the stroke did it right off the bat
Theres no right answer depends on what you can tolerate.

 

Much, much easier and economical for you to add a mild-med cam with good driveability to pick up additional power with your current setup.

 

Think this way,

The larger the bore, the shorter the stroke, the faster/higher the engine wants to rev, but your giving up lower end torque instead.

Hence the older v8 F1 engines that reved to 20k, had bores of 3.858 inches, while the stroke of the engines where only 1.566 inches.

The longer the stroke, the smaller the piston, the more you are making lower torque instead, but at the same time, the less the engine will want to higher rev. Think diesel engines engines.

Now at some point, there is only so far you can rev a motor before mech type vavles can keep up with it, so if you want a motor that is going to rev past say 10k, then your into electronic valves to keep up with the motor instead.


Hence take a LS-7, and it can make more power buy just de-stroking it down to a 383 with it reving to 8K (and getting to breath at that rmp correctly), than trying to stroke and bore it and ending up with a motor that can not rev/breath to the 7k mark instead.

 

Stroke is the length of piston travel 4 inch in the ls7 is really good for stroke no need to add any further stress there.

Bore out is to increase piston diameter, a no no in the ls7 as the cylinder bores in the ls7 are particularly thin wall as they come.

I suggest a set of Tony Mamo cylinder heads and a Tony Mamo spec camshaft that should bump your whp up by at list 100 and an ear to ear smile seals the deal.

https://www.mamomotorsports.com/