Bore vs. Stroke, a little math

[WFO]

I like to watch the show, but don't consider that street racing. More like racing on a closed down street.
There are no car haulers in street racin.
I also consider Doc a dick head.

 

[Honky Kong jr]

I like to watch the show, but don't consider that street racing. More like racing on a closed down street.
There are no car haulers in street racin.
I also consider Doc a dick head.

Don’t forget a whiner although he does actually have a car that isn’t a promod though.

 

[WFO]

Don’t forget a whiner although he does actually have a car that isn’t a promod though.

I do like his car, just not him.
They pretty much all moved away from the promods last season.

 

[Honky Kong jr]

I do like his car, just not him.
They pretty much all moved away from the promods last season.

Yes I too like his car and I guess that shows how much I don’t watch it lol I’d love to see them run the Hot Rod thing that Larry does where they have to drive them on the street 1000 miles. But then again if something breaks they have to have theirs crews along to fix it until it was time to carry the turbo over to the car. Lol

 

[vkh]

That **** just makes my head spin.

i'm generally a fan of longer stroke both on the street for the torque---better for towing/hauling/general driving below 3000rpm. AND at the strip; i still think longer stroke prevails despite the possibility of more friction for a longer stroke vs. larger bore (and i'm not totally convinced this is the case either).

Yeah, in the real world I'll take all the cubes I can get regardless if it's from bore or stroke. I do think in an all else equal scenario they'd behave more similar than most people would guess. (That is as long as you aren't revving until stuff breaks)

 

[vkh]

I think, long as You dont throw a bunch of alphabets into the equation, I wont get all frustrated and confused.

lol, fair enough

 

[vkh]

I was always under the impression the additional torque was created by the mass of the heavier stroker crank once it gets spinning. E=mc^2 (mass x velocity squared equals energy, or torque. Increasing either mass which we can interpret as the weight of the crank, or velocity which we can interpret as rpms will result in more torque). The same as a loaded 200 car freight train takes a mile to stop where the same train unloaded may only take 1/4 mile, once that mass is in motion it takes a lot to stop it. Much like a torque converter makes more torque than a standard's flywheel, more mass in motion creates more force. They say there's no replacement for displacement though, I'm sure there are a lot of other dynamics that have to be factored in when you consider a simple cam swap can result in more torque. Or does it just shift the torque curve to a lower rpm range that you feel seat-of-the-pants sooner? But I digress, I'm beginning to ramble lol.

I think you're looking for ke=1/2mv^2 for kinetic energy. e=mc^2 relates mass directly to energy, c is the speed of light. I'ts what accounts for the loss of mass in nuclear reactions, it's atomic energy rather than kinetic. But back to kinetic, the mass of the crank would be some stored energy which would help a touch say when putting it in gear. But for continuous loads you have to add just as much energy as is lost to stay up to speed as you would with a lighter crank. And in a car the mass of the crank would be pretty small compared to rest of the rotating components like driveshafts, axles, wheels, ect. Flywheel effects are useful for overcoming sudden loads but you still have to be able to replenish all the energy used right afterwards.

And I believe the torque converters has additional torque is due to the nature of the fluid coupling. It almost acts as a little variable transmission depending on the load on it. There is actually a car out there that just uses a torque converter instead of a transmission, the Koenigsegg Regera.

xc_hide_links_from_guests_guests_error_hide_media

I think with cams it depends on the purpose. If you're replacing a stocker 80s cam you can get more torque everywhere since they were detuned for smog. But if these are well designed cams I think your mainly shifting your peak torque up and down the curve.

 

[HotRodPC]

I like to watch the show, but don't consider that street racing. More like racing on a closed down street.
There are no car haulers in street racin.
I also consider Doc a dick head.

Exactly. It's not only a closed down street, it's a closed down filming set. Many police and security are hired to keep everyone without a pass out. NO public spectators whatsoever allowed anywhere near the set. The ONLY thing about it that is Street Racing is that its on a street and not a track. Ohhh and the ******** and smack talk is true street racing. If you can't see it for it's entertainment value, then no need to watch it because that's all it is. But, these guys still do street race. There's the list for the show, then there's the list. Of course the show is 4-6 months behind.

 

[vkh]

A larger bore will also allow bigger valves, which allow better cylinder filling.

A longer connecting rod will have less angularity on the crankshaft throw, allowing a longer application of torque during the rotation.

Very true, I was mainly wondering if all else was equal are they as different as conventional wisdom says. My example isn't very useful for real world, really just a hypothetical in my head that I found the results interesting. I'm an engineering student so when I see a way to apply alittle of what I learned to my passion I get excited. Ultimately the average guy is limited to what engines came in cars, which are largely bore limited, so stroke is the way to go for most people.

 

[vkh]

Ohhh, and I've also heard that comparing all the GM 350's to each other, cuz other than Cad, there was a Chevy, Buick, Olds, and Pontiac 350, and if asked which one of the 4 would put out the best power all things considered being alike. It's said the Olds 350 should perform best due to being so close to a Square bore x stroke ratio as in for example without looking it up, 3.75 bore x 3.75stroke. So if that's true, your 4.5 x 4.2stroke combo would be the one to use Instead of the 3 x 5 combo.

Do you know what the reasoning behind square dimensions being best is? I've heard it several times but never with the logic behind it.

 

[vkh]

BIG BLOCK!!!

Lol, biggest bore and biggest stroke, Best way to go!

 

[fussfeld]

i don't have time to get into it whole-hog right now, and may not any time soon but if i was going to be doing any towing----and really that's one of the reasons for a truck, i would rather have a 383 (350 block with 400 stroke, 3.75") vs. a 377 (400 block with 350 stroke, 3.48") even if the 377 will likely rpm higher.

 

[crazy4offroad]

You can do standard bore 350 with 400 crank and make 377 cubes as well, may be more torquey than an understroked 400.

 

[vkh]

i don't have time to get into it whole-hog right now, and may not any time soon but if i was going to be doing any towing----and really that's one of the reasons for a truck, i would rather have a 383 (350 block with 400 stroke, 3.75") vs. a 377 (400 block with 350 stroke, 3.48") even if the 377 will likely rpm higher.

I think the 377 would be more similar to the 383 than most people would expect within a reasonable rpm range. I wish I could find an all else equal comparison between the two, kinda tricky because anyone who builds a 377 is planning to rev the **** out of it from the gate and builds it accordingly.

 

[SkinnyG]

I did a wack of Googling to compare a 377 (400/350crank) and a 383 (350/400crank). The consensus - especially among the circle track crowd - is that the 383 just has a whole lot more usable torque, despite more valve shrouding. And if you had a 400 block, just build a 408.

The 377's beat all the 350's, then the 383's beat all the 377's, then the 408's beat all the 383's.

I went looking because I have a line on a good 400 block, and I have a good 350 crank, and got curious.