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  #16 (permalink)  
Old 07-30-2008, 04:08 PM
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Quote:
what about caddy?
The stroke on the Caddy 500 is 4.304" with a 4.300" bore.... but there is nothing "small" about that block. Its weight is pretty light, but its a huge engine

Is there a particular reason why the long stroke? If you're looking for torque, they will all make almost identical torque, so why not go with the cheapest/easiest engine?

The old idea that longer strokes make more torque has been disproven many times.

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  #17 (permalink)  
Old 07-30-2008, 04:23 PM
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Quote:
Originally Posted by curtis73
The stroke on the Caddy 500 is 4.304" with a 4.300" bore.... but there is nothing "small" about that block. Its weight is pretty light, but its a huge engine

Is there a particular reason why the long stroke? If you're looking for torque, they will all make almost identical torque, so why not go with the cheapest/easiest engine?

The old idea that longer strokes make more torque has been disproven many times.

no,.. long stroke= high torque.otherwise we would be refused the physics laws.

but if you have long stroke, your piston has double or triple long way to go in the same time.so your engine cant rotate high rpm cause of inertia.

high rpm=high hp

but if you want high torque and high hp in the same engine you should have long stroke and super light pistons and rods like forged cp ones.

you should equalize this formula. mass1 X speed1 = mass2 X speed2
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Old 07-30-2008, 09:55 PM
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???

Want a long stroke in a small block? Get yourself a 400 Chevy and put a 4.00" crank in it. 427 cubic inches.

Aside from Cadillac, Buick V8s are probably the most difficult GM engines to find aftermarket parts for. They are out there but in somewhat limited numbers and are often quite spendy.
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Old 07-30-2008, 10:18 PM
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My Turkish friend, you are forgetting about the swing of the crankshaft in the crankcase. If the stroke is to long the rod ends will hit the sides of the block just like they do when you put a 400 crank in a 350 Chevy block to make a 383 engine. The wrist pin in the piston would also have to be moved, so as not to put the piston through the roof (head). Read up on center line distances of rods and pistons, as well as crankshafts of different GM engines.

If you want high horse power for your Buick engine, add twin turbo chargers, a blow through Demon carb, and a 150 shot of nitrous. That will get your torque up!
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Old 08-24-2008, 04:40 PM
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Err well, Chevy had the only "small block", the other three used the same basic architecture for everything from 350's to 455's.
olds and pontiac had basically the same block and dimensions for their 350-455 engines. The Buick 350 was a totally different engine than the 400-455 engines. while the buick 350 is more expensive to buy parts for, it is in fact very easy to make a big flat torque curve with a buick 350. a Buick 350 crank will withstand up to 700 horsepower and the stock rods will handle 500 hp safely. aftermarket forged pistons are available through several sources.
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Old 08-24-2008, 04:59 PM
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Quote:
Originally Posted by daturkishulan
no,.. long stroke= high torque.otherwise we would be refused the physics laws.

but if you have long stroke, your piston has double or triple long way to go in the same time.so your engine cant rotate high rpm cause of inertia.

high rpm=high hp

but if you want high torque and high hp in the same engine you should have long stroke and super light pistons and rods like forged cp ones.

you should equalize this formula. mass1 X speed1 = mass2 X speed2
While your physics make sense, it just isn't true in practice. Its been proven in countless dyno tests side by side. I'm not talking about RPMs, I'm talking about net torque on the crank. Its true that shorter strokes lend themselves to higher RPM potential due to inertia, but the fact remains... build a Buick 455 and an Olds 455 with the same specs (or as close as you can get) and you'll find nearly identical torque outputs at the same RPM. The Buick may have a shorter stroke, but it still has 455 cubes (and proportionally larger piston surface area) to push on the crank.

Shorter throw + larger pistons = same displacement and approximate net torque at the crank.

Now... if you JUST increase stroke you are putting the same force on a longer lever. The increased displacement lowers the torque peak RPM, while the longer lever makes more net torque. In that case, it would be:

Longer throw + same size pistons = larger displacement and more net torque

For this reason, I always choose the shorter stroke (read - oversquare) build... well, ALMOST always. You can build them for the same street torque, but the short stroke engine has more RPM potential if you decided to up the ante later. The long stroke will almost certainly be doomed to an eternity of low RPMs - which is fine if that's what you want forever.

And anyone who says that short stroke can't make just as much torque hasn't dynoed many Buick 455s

Last edited by curtis73; 08-24-2008 at 05:06 PM.
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Old 08-24-2008, 05:37 PM
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One of the biggest reasons the Buick 455 makes such big torque numbers is the small intake runners and high velocity of the incoming intake charge. the 3.9" stroke isnt short by any means and the 4.3125 bore is large enough to have plenty of surface area for the ignited gas to press down upon. a buick 401 maKES 445 FT lbs of torque in stock form for the exact same reason. it has a 3.64 stroke and a 4.1" bore but has very small intake runners and a very fast moving intake charge.
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Old 08-24-2008, 10:49 PM
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Quote:
Originally Posted by Buick Special
One of the biggest reasons the Buick 455 makes such big torque numbers is the small intake runners and high velocity of the incoming intake charge. the 3.9" stroke isnt short by any means and the 4.3125 bore is large enough to have plenty of surface area for the ignited gas to press down upon. a buick 401 maKES 445 FT lbs of torque in stock form for the exact same reason. it has a 3.64 stroke and a 4.1" bore but has very small intake runners and a very fast moving intake charge.
True, but I was simply using those examples since they had the same displacement with different bore/stroke ratios.... and thousands of dyno runs to back up my claims
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