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Re: Which is Faster, Bore & Stroke ? [Re: cudaman1969] #2891883
02/22/21 01:45 PM
02/22/21 01:45 PM
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Looking at motor acceleration which will accelerate faster, short or long stroke ?
The longer stroke should pull in more air and fuel but the ring friction on the longer stroke comes into play as well as how long the power stroke, pulses, pushes down on the pistons work shruggy
I think the larger piston top exerts more pressure on the crankshaft than the longer stroke does shruggy work grin
Which makes me think the bigger bore will, and does, makes more power compare to the longer stroke when trying to make the same C.I. motors shruggy

Last edited by Cab_Burge; 02/22/21 01:49 PM.

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Re: Which is Faster, Bore & Stroke ? [Re: Al_Alguire] #2891886
02/22/21 01:56 PM
02/22/21 01:56 PM
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Originally Posted by Al_Alguire
7000 rpm is the limiting factor IMO. Would likely flavor more stroke. But generally a bigger bore will make more power than more stroke, but when you are talking BB Mopar the bores are not very large for sure. The old saying bore makes power stroke moves where it happens.
the only factory engine with a bigger bore is a 460 Ford. The 454 is 4.25 puke that is why there are so many aftermarket blocks for them. The 396/454 engines with rectangle heads have huge bore notches from the factory, the 396's are only 4.096. The un-notched oval port engines are only a 2.06 intake valve...........advantage Mopar. Bigger bore , larger valve. And when they did settle on a 4.25 bore they knew the only way to get a big valve un-shrouded was hemispherical.

Re: Which is Faster, Bore & Stroke ? [Re: B1MAXX] #2891928
02/22/21 04:11 PM
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Horsepower is a function of torque, torque is a function of force over a lever,
Force, in this instance is a function of pounds/ sq inch.
So a larger bore provides (at the same peak pressure) more psi.
Limiting it to 7k rpm reduces this variable, but the higher psi will make more
horsepower.
I'm not an engineer, but an engineering student. Prove me wrong, and
show me where the crossover occurs.


It may be ugly, but it sure is slow.

Girls comb their hair in rear view mirrors and the boys try to look so hard....
Re: Which is Faster, Bore & Stroke ? [Re: Dragula] #2891952
02/22/21 05:19 PM
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Re: Which is Faster, Bore & Stroke ? [Re: poboyengineering] #2891958
02/22/21 05:32 PM
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Two engines same brand, Ford 427 and 428, which is faster? BTW those aftermarket Chevy blocks were made to get those big cranks-long rods in there for 900 cu in. Chevy block has very short deck. NASCAR dictated that bore-cubic in size for all 3

Re: Which is Faster, Bore & Stroke ? [Re: cudaman1969] #2892009
02/22/21 08:09 PM
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I look at it this way. If the motor is going in a light car you don't need the extra torque, so short stroke would be better to get RPM's up faster. With a heavy car you want the extra torque longer stroke to get things rolling.

Re: Which is Faster, Bore & Stroke ? [Re: cudaman1969] #2892013
02/22/21 08:14 PM
02/22/21 08:14 PM
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Originally Posted by cudaman1969
Two engines same brand, Ford 427 and 428, which is faster?


Perfect example


[img]http://i.imgur.com/boeexFms.jpg[/img]
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Re: Which is Faster, Bore & Stroke ? [Re: cudaman1969] #2892026
02/22/21 08:43 PM
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Originally Posted by cudaman1969
Two engines same brand, Ford 427 and 428, which is faster?

Which HP version of those two C.I. motors are you asking about?
I'm not a Ford racer nor do I know much about those two F.E. motors but I have raced against them and even freshen a 1966 or1967 Holman and Moody boat 427 medium riser side oiler that had the inline dual Holley vacuum carbs. that had the 105 CC NASCAR wedge heads on it for a friend and neighbor shock
He also had two 428 out of junkyard cars, one was a 1967 or 1968 Thunder Bird and the other one was out of a full size Ford station wagon around the same year as the T bird .
The 1967 Shelby 428 motors and 1968 428 GT Mustang motors and the 1969 and 1970 Cobra Jet motors where rated at a different HP than the other 428 Ford install in their regular non HP passenger cars back then shruggy
I liked the 427 motors the best of the two up

Last edited by Cab_Burge; 02/22/21 08:46 PM.

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Re: Which is Faster, Bore & Stroke ? [Re: Dragula] #2892031
02/22/21 08:57 PM
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Too many variables, there is no single answer.
I'm too tired to answer all the mistakes.


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Re: Which is Faster, Bore & Stroke ? [Re: Cab_Burge] #2892032
02/22/21 08:59 PM
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A friends 68 Mustang race car I drove. All eight mile. 427 tunnel port two fours could only muster 7.00 c-6 and 8” vert and 4.88 gears. Same combo except a 428 CJ- single 4- 7.10, IF we had a four speed I’m sure that TP would have been faster, felt lazy off the line. Both engines were basicly stock with a good cam. LOL we put a 250 Horse no2 on the 428 and went some 6.40s, that was a kick in the ass, 10.57 in the 1/4, never heard it shift, blew right thru the vert. Way back in early 80s

Last edited by cudaman1969; 02/22/21 09:01 PM.
Re: Which is Faster, Bore & Stroke ? [Re: Dragula] #2892061
02/22/21 10:38 PM
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Originally Posted by Dragula
Lets say rpm limit is 7k and engine size is 555.....There are a number of combinations to get near the cube limit, but which would be quicker? A smaller bore and big stroke, or a big bore small stroke?


Let me ask you this.....What's the weight of the vehicle ? if it's 2600lbs Dart well sorted out chassis with a power glide, 4.500X4.375 , a 4500lbs 2014 Charger .....I'd go 4.40x4.55 and as many gears I could fit behind it.

Re: Which is Faster, Bore & Stroke ? [Re: Taylor] #2892078
02/23/21 12:09 AM
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340 vs. 360 popcorn


If the results don't match the theory, change the theory.
Re: Which is Faster, Bore & Stroke ? [Re: Dragula] #2892121
02/23/21 08:01 AM
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More bore + more intake valve area = more hp.

Not some, not most, ALL the time.

Re: Which is Faster, Bore & Stroke ? [Re: LSP] #2892133
02/23/21 08:40 AM
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Re: Which is Faster, Bore & Stroke ? [Re: B1MAXX] #2892153
02/23/21 09:31 AM
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Originally Posted by B1MAXX
the only factory engine with a bigger bore is a 460 Ford. The 454 is 4.25 puke that is why there are so many aftermarket blocks for them. The 396/454 engines with rectangle heads have huge bore notches from the factory, the 396's are only 4.096. The un-notched oval port engines are only a 2.06 intake valve...........advantage Mopar. Bigger bore , larger valve. And when they did settle on a 4.25 bore they knew the only way to get a big valve un-shrouded was hemispherical.



Was not aware the OP was referring to factory blocks. I would assume since he is talking about 555" engine size on a Mopar site. So in my feeble mind we are talking aftermarket parts thus making factory dimensions a moot point in this discussion. I get it that Mopar guys have to defend the mother ship at all costs but in the instance of this discussion its irrelevant what the factory dimensions are.

Ask anyone who is a Chevy drag racer which engine will run better a 555 or a 565. Anyone with any experience will pick the 565 all day long and twice on weekends. The difference, the bore size..

Re: Which is Faster, Bore & Stroke ? [Re: Al_Alguire] #2892157
02/23/21 09:40 AM
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The path to NA horsepower would be running the biggest bore, shortest stroke that would fit the block used, and or desired end engine displacement... ( ie...cubic inches)...IMHO


Curator at Adams County Speed Shop
Re: Which is Faster, Bore & Stroke ? [Re: 340man4ever] #2892162
02/23/21 09:44 AM
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Comp Eliminator is a performance based cubic inch "limited" class. I don't know of ANYONE who chooses stroke over bore to get to the desired cubic inch number. Even the two blown SB combos I am aware of.

Re: Which is Faster, Bore & Stroke ? [Re: cudaman1969] #2892170
02/23/21 09:52 AM
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Originally Posted by cudaman1969
You don’t understand, ya gotta play with what you have available. Really like to see some of these 5” bore mopar engines. Like hitting a nail, short swing, nail won’t go deep, big swing that nail going clear thru. Bigger hammer might help a little but big swing gets the job DONE. One of the 5 basic tools, a lever!



That’s what the transmission and rear axle are. Levers. You can move more with gearing than you ever will with stroke.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Which is Faster, Bore & Stroke ? [Re: Al_Alguire] #2892234
02/23/21 12:05 PM
02/23/21 12:05 PM
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Originally Posted by Al_Alguire
Originally Posted by B1MAXX
the only factory engine with a bigger bore is a 460 Ford. The 454 is 4.25 puke that is why there are so many aftermarket blocks for them. The 396/454 engines with rectangle heads have huge bore notches from the factory, the 396's are only 4.096. The un-notched oval port engines are only a 2.06 intake valve...........advantage Mopar. Bigger bore , larger valve. And when they did settle on a 4.25 bore they knew the only way to get a big valve un-shrouded was hemispherical.



Was not aware the OP was referring to factory blocks. I would assume since he is talking about 555" engine size on a Mopar site. So in my feeble mind we are talking aftermarket parts thus making factory dimensions a moot point in this discussion. I get it that Mopar guys have to defend the mother ship at all costs but in the instance of this discussion its irrelevant what the factory dimensions are.

Ask anyone who is a Chevy drag racer which engine will run better a 555 or a 565. Anyone with any experience will pick the 565 all day long and twice on weekends. The difference, the bore size..


Only pointing out from the factory Mopar was on the right track big bore (bigger valve),short(er) stroke.

Re: Which is Faster, Bore & Stroke ? [Re: LSP] #2892238
02/23/21 12:10 PM
02/23/21 12:10 PM
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Originally Posted by LSP
More bore + more intake valve area = more hp.

Not some, not most, ALL the time.

The evolution of most any normally aspirated performance engines bears this out.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
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