Hot Rods Motor to motor

After cubic inch, bore/stroke ratio is the most important thing to the power an engine's going to make and how it's going to act in general. For example anyone who's had both a 377 and a 383 SBC knows that they have much different manners.

Then it's on to cylinder heads, but the bore still limits what you can do for valve size and chamber configuration.

 

If everything was equal, horsepower and torque would be equal as well.

 

Finally, that´s the perfect answer right there. Every manufacturer designed their engines for a different purpose using slightly or completely different approaches for costumers with different budgets and tasks. I´d think a Porsche 356 driver would righfully complain about a big blown hemi in the back of his road track car...

 

364 Buick Nailhead provides torque, rpm and best looks in an engine package.

 

I owned a new Chevy 283 and a used 1954 Hemi 241 and the Hemi wins the torque bet hands down. Chevy wins the HP but put some higher compression and carbs on theHemi ( which I now own and my 270 Dodge hemi wins.

 

I think the Engine Masters competition lately has been a pretty good judge here. For the most part, the magic is in the heads, and for a factory pre-2000's era motor, hands down the 351 closed chambered Cleveland ford heads outbreath anything else per/cubic inch. Fix the couple of oil system issues with a cleveland and they can produce some staggering hp numbers.

 

like how a 265 from 1956 makes more everything than a 305... from really any year. cubic inches arent everything.

 

Objectively... If you compare many naturally aspirated american V8 engines to performance engines from other parts of the world this becomes rather obvious. They often lack the ability to breathe well so while the large displacement produces lots of torque at low rpm (which equals descent power at those rpms), but as rpms go up asthma strikes and when they should be able to produce crazy amounts of power they're struggling to do anything at all.

 

Old timers used to say that the “ perfect” engine was a “ square” engine….that is when the bore and stroke are the same! I just heard it, not saying it’s true! But it does have a nice ring to it! Lol






Bones

 

Leave them all at the curb with a “free” sign.
See which one is gone first.

 

For twostrokes it's true, it's generally the best compromize there. The loop scavenging tends to work poorly in designs too over- or undersquare.

In fourstrokes you have more freedom to choose what bore vs. stroke you want.
With a short stroke vs. big bore you get an engine that mechanically can handle high rpm (short stroke means small forces on the piston etc. when accelerating & decellerating every revolution, forces are relative to rpm^2 so they go up fast as rpm increases).
You also get lots of room for big valves, that can keep up and feed that cylinder at very high rpm, while the downside may be that big valves and corresponding ports etc. may not perform great at low rpm.

Long stroke, small bore engines are limited rpm wise due to big forces on the piston etc, and the small valves you are limited to will unable to let the cylinder breathe good enough at high rpm anyway. On the other hand, the small valves, small ports etc. will provide high gas velocity already at low rpm, so the engine has potential to work well at low rpm.

 

Well said!






Bones

 

Every engine I would consider "performance" is oversquare. Even a lowly 305 SBC is slightly oversquare.

Then just for giggles I Googled some older engines that I'm not as familiar with. Was surprised how many were way undersquare.

So I suppose there was a time sixty years ago that just getting to square was a step up.

 

Yes, especially when a lot of the engines were flatheads. When the valves and ports are next to the cylinder bores in the same housing, the only way you're going to have 4 inch bores is by having a large, very heavy block.