FYI: How Bore & Stroke affect Cubic Inches

[DominusEtDeusNatus]

1ci, 5ci, still not worth doing. Way to much money for way too little gain.

[Dominic]

Well when you're talking 400bhp from a blown V6, then all of a sudden you stroke her and gain 15-20hp... you find that... its still not worth the gain :D

[strange_trp]

playing with bore/stroke can also affect the engine's powerband, sometimes adversely if you don't know what you're doing.

this is not probably a worthwhile mod to do for the sake of doing it, but if you will be rebuilding your engine anyway and you have the knowledge to know how the powerband will be affected by changing bore/stroke, i'd say go ahead while you're already there inside the engine. it doesn't cost that much more to have a block bored than it does to have the same block simply reconditioned at a good machine shop.

with that said, i should also say that this is a mod that will only show you its true benefits with other mods, like valvetrain work, FI or NOS.

[Patrick Javert]

By getting a longer stroke, you move the powerband lower in the rpm range. Less rod ratio also contributes to moving the torque and hp peaks lower in the powerband. After getting forced induction installed on your car, you should look into boring and/or stroking your engine since the hp/tq gains will be multiplied and it allows you to get stronger and lighter internal components installed as well as new gaskets and seals to stand up to the pressure you will be putting on your engine. The only reason I will bore my engine out eventually is to be able to fit larger than stock valves in my engine without worrying about shrouding or any other problem involving clearance.

[strange_trp]

sometimes a block must be bored to recondition it properly. if this is the case i'd recommend minimum (like .010) unless you are modding and could use the extra .010.

what gets tricky is when guys want to play with bore and stroke at the same time. yes generally changing stroke changes the powerband placement in the rpm range, but this is with a constant bore. changing both is a bit more difficult to predict changes in ulitmate performance. and like i mentioned before, performance gains will depend greatly on the other mods that will allow bore/stroke to be fully utilized for the particular application.

[Patrick Javert]

Bore doesn't really move the peak in the powerband around a lot. Most likely increasing bore will move it up the powerband. and yes it does matter what you have on your car/what you have done to your car.