"Square" Engine Practical ?? - Chevelle Tech
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post #1 of 37 (permalink) Old Jul 12th, 19, 11:31 PM Thread Starter
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Scott
 
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"Square" Engine Practical ??

This is just out of curiosity, not looking to build one.

At some point in the past, I read an article about "square" engines. I only remember it due to them being named as such. If your not familiar with the term, if I remember correctly, a square engine is where the bore and the stroke are the same?

I believe the article alluded to, that these engines can rev much quicker then those with the more common bore to stroke dimensions. So, are such engines practical on the street? Or, are they more at home on a track?
In my mind, an engine that can rev quicker would be at an advantage on road courses, autocross tracks, and maybe even on the street, since theoretically, said vehicle should be able to increase their speed at a quicker rate then their competition running the more common engine bore to stroke differences, with all else being equal?

Am I missing something? I've searched google for "square engines", but I am not getting anything. Anyone know where I can read up on these engines? Maybe using the term square is not correct?

Thank you in advance.
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post #2 of 37 (permalink) Old Jul 13th, 19, 12:15 AM
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Re: "Square" Engine Practical ??

Not even close to being true. A 302 has a four inch bore and three inch stroke. Increase the stroke to four inches and you would have a stone. A stone with lots of torque, but still a stone.

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post #3 of 37 (permalink) Old Jul 13th, 19, 12:55 AM
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Re: "Square" Engine Practical ??

Lots of 4" squared LS engines are out there. They are hardly stones.
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post #4 of 37 (permalink) Old Jul 13th, 19, 1:39 AM
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Re: "Square" Engine Practical ??

I don't think square has any magic to it. Been said many times, its all about the combo

Personally I like big bore, short stroke engines. But I also like road racing that sustains RPM's.

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post #5 of 37 (permalink) Old Jul 13th, 19, 1:50 AM
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My 489 is effectively square.... 4.28x4.25 sbc runs great! Revs quickly. I can say a stock 454 does well with a decent cam too.
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post #6 of 37 (permalink) Old Jul 13th, 19, 6:34 AM
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Re: "Square" Engine Practical ??

My 513 CI BBC is pretty much square too,4.32 in. bore X 4.375 in. stroke.
Mike Lewis picked out the rotating assembly,heads & cam.
It works real nice and revs pretty darn quick.
The guy's at the dyno were impressed !!
As has been said many times,it's all in the combo.
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post #7 of 37 (permalink) Old Jul 13th, 19, 7:31 AM
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Re: "Square" Engine Practical ??

Square, overbore, oversquare ( tractors). other than low speed TQ ( oversquare). and spooling up turbos ( overbore ) it not all that relevant anymore.

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post #8 of 37 (permalink) Old Jul 13th, 19, 7:38 AM
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Re: "Square" Engine Practical ??

I'm having a short block built now that's 4.28" bore & 4.25" stroke= 489, rotating ass. from Mike Lewis and I hope it's no stone lol, It's proven it's all about the combo but I wonder how a 4.25X4.25 with the right combo would run?


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post #9 of 37 (permalink) Old Jul 13th, 19, 7:43 AM
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Re: "Square" Engine Practical ??

Quote:
Originally Posted by shovelrick View Post
I'm having a short block built now that's 4.28" bore & 4.25" stroke= 489, rotating ass. from Mike Lewis and I hope it's no stone lol, It's proven it's all about the combo but I wonder how a 4.25X4.25 with the right combo would run?
I wouldn't worry about it too much,Mike knows how to pick out parts that will work just fine.
He can help with camshaft selection too,the UDHarold custom grind that him and Tim at Bullet picked out for me works great !!
Guy
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post #10 of 37 (permalink) Old Jul 13th, 19, 8:56 AM
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Re: "Square" Engine Practical ??

The manufacturers have exploited the bore to stroke ratios for the best compromise between performance and economy. Those configurations, while not necessarily perfect, would be hard to improve upon significantly. As others have said, itís about optimizing an existing configuration, the combination.

The only reason you would worry about the bore to stroke ratio would be for a special performance in a formula that is maybe displacement limited or a road race car, or top end performance application. When you build something like that you are making compromises in other areas of the horsepower and torque curve.
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post #11 of 37 (permalink) Old Jul 13th, 19, 1:59 PM Thread Starter
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Scott
 
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Re: "Square" Engine Practical ??

Appreciate ya'll. I can get around on the outside of the block, but everything inside is all voodoo to me. I get it's all in getting the right combo, cam lift, etc. I'm just being curious. I'll sit back now and just let all you knowledgable people discuss this and we'll see what I can learn.

Thanks folks, and have a blessed day.
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post #12 of 37 (permalink) Old Jul 13th, 19, 3:30 PM
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Re: "Square" Engine Practical ??

Quote:
Originally Posted by dyno jonn View Post
Not even close to being true. A 302 has a four inch bore and three inch stroke. Increase the stroke to four inches and you would have a stone. A stone with lots of torque, but still a stone.
Lot's of 496 inch Rats out there that are far from being "stones".

If you put a 4 inch stroke in a 302, it would have the potential to make quite a bit more power than the original, just at a different RPM. Of course, component matching, particuarilly in the heads and cam, would be very important.
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post #13 of 37 (permalink) Old Jul 13th, 19, 8:05 PM
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Re: "Square" Engine Practical ??

"Square" means nothing in itself.

Restricting the bore size also restricts the valve size, and therefore the port size. Restricted valve/port breathing tends to shift the power band lower in the RPM range.

Similarly, a longer stroke and smaller bore tends to increase average and peak piston speed for a given RPM, which also tends to reduce max RPM as the stresses on the bottom-end increase compared to a short-stroke, big-bore engine.

Long-stroke engines are "what you can do" to increase displacement in engine blocks that don't have enough cylinder-wall thickness to accept massive overbores.

So, for example, the tight bore spacing on the Oldsmobile V-8 limits the bore size while keeping 360-degree coolant around the cylinders. Therefore the 455 Olds has a 4 125 bore, and a 4.25 stroke. A Buick 455 has much larger bore spacing, so it's got a 4.31 bore and 3.90 stroke. But both engines have small ports and valves, so both engines are known for low-speed torque. It's the valves and porting that determines the power band speed.

And the Caddy 500 has a nearly-square B 'n' S, at 4.300 bore, 4.304 stroke, but nobody would call it a fast-revver.
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post #14 of 37 (permalink) Old Jul 13th, 19, 8:36 PM
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Re: "Square" Engine Practical ??

One of the rags did a few tests several years ago with several different configurations - long stroke/small bore, square, and short stroke/big bore. While none was truly optimized to take advantage of its particular configuration, the conclusion is that cubes is cubes. The expanding gasses act longer on the long stroke but the size of the piston top provided more cubic inches for that charge to act on.

I like short stroke/big bore for stronger crankshafts (thanks to more journal overlap) and better breathing characteristics of the big bore. I've seen some long stroke engines rev like crazy, though...

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post #15 of 37 (permalink) Old Jul 14th, 19, 8:30 AM
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Re: "Square" Engine Practical ??

I bet my 565 revved quicker than a lot of square engines and was 4.6 bore with a 4.25 crank. And it still went to 7800 in the lights. So we can squash the big blocks canít go past 6000 theory too while weíre at it.
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