Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891663
02/21/21 09:05 PM
02/21/21 09:05 PM
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Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
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Bigger bores mean more reciprocating weight and more drag.
I imagine the proper answer is a nice blend of the two.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891681
02/21/21 09:46 PM
02/21/21 09:46 PM
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Joined: Feb 2003
Posts: 1,098 Massillon, Ohio
cudatom
super stock
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super stock
Joined: Feb 2003
Posts: 1,098
Massillon, Ohio
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Not sure but I ended up going with 4.5 bore and a 4.35 stroke. Using 7.1 rods with 2.2 rod journals. Ends up being a tad over 553 CI.
Ok
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Re: Which is Faster, Bore & Stroke ?
[Re: cudatom]
#2891691
02/21/21 10:08 PM
02/21/21 10:08 PM
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Joined: Jan 2003
Posts: 7,475 Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,475
Minnesota
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On gasoline, the biggest bore possible makes the most power, because moving the cylinder wall away from the valve improves flow. Assuming adequate cylinder wall thickness for effective ring seal.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891692
02/21/21 10:10 PM
02/21/21 10:10 PM
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Joined: Feb 2021
Posts: 70 Souderton
Taylor
member
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member
Joined: Feb 2021
Posts: 70
Souderton
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Wedge or Hemi ? Wedge the big bore Short stroke seems to be the go to...... Canted valve leans towards Big Bore short stroke also .... for Hemi....... I don't think it matters as much.
Current Pro stock thinking is 4.71-4.75 bore and stroke in the 3.5, 3.55 depending on deck height rods are in the 5.95-6.10 range .Last DRCE my uncle built was a 8.70 DH , 4.71X3.55 with 6.10 C to C rods.
04 Ram 4x2 11.66@ 122 4750LBS ...phat pig Moves for fully loaded truck with NA 345ci Hemi 2020 1320 Challenger....stock daily driver.
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Re: Which is Faster, Bore & Stroke ?
[Re: Taylor]
#2891698
02/21/21 10:39 PM
02/21/21 10:39 PM
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Joined: Jan 2004
Posts: 8,233 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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Stroke will make more power, most engines can only go .060 but you can stroke them 1/2 inch or more. Chevy, I know I know, 427-4.25 bore x 3.75 stroke, 454 4.25 bore x 4.00 stroke, which makes more power turning same rpm?
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Re: Which is Faster, Bore & Stroke ?
[Re: Twostick]
#2891725
02/22/21 12:39 AM
02/22/21 12:39 AM
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Joined: Dec 2005
Posts: 11,484 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,484
Fulton County, PA
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500 inch blown fuel engines are long stroke, small bore. 500 inch gasoline ProStock engines are big bore, short stroke.
Torque monster - more stroke. Peaky high RPM - big bore, big valves.
7k limit would favor a long stroke.
If the results don't match the theory, change the theory.
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Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891729
02/22/21 12:58 AM
02/22/21 12:58 AM
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Joined: Nov 2015
Posts: 873 Missouri
jwb123
super stock
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super stock
Joined: Nov 2015
Posts: 873
Missouri
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From my experience, you want the biggest bore, and still keep the cylinder walls thick enough they do not flex, you don't make any power if the rings don't stay sealed under power. And on the dyno testing, just keeping track of the engines I dynoed, the peak numbers may be close, but those that I did the average HP numbers were always higher on the big bore engines, and higher average numbers usually will out run higher peak numbers given the same chassis combination. The best example was to 383 small block chey's I built for mud jeeps. One was a 350 block stroked, the other was a 400 de-stroked. The 350 had some better heads, and made about 20HP more, but the 400 had better average numbers, in the mud pit, the 400 jeep smoked the 350 block.
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Re: Which is Faster, Bore & Stroke ?
[Re: CMcAllister]
#2891740
02/22/21 02:20 AM
02/22/21 02:20 AM
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Joined: Jan 2003
Posts: 7,475 Minnesota
Hemi_Joel
master
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master
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Minnesota
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500 inch blown fuel engines are long stroke, small bore.
7k limit would favor a long stroke. The fuel motors really need the wall thickness. Plus the slow burning nitro doesn't mind the long stroke.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Which is Faster, Bore & Stroke ?
[Re: Twostick]
#2891792
02/22/21 10:27 AM
02/22/21 10:27 AM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
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master
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Posts: 4,205
New York
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Same heads, cam and induction
That's the reason.
Boffin Emeritus
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Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891841
02/22/21 12:31 PM
02/22/21 12:31 PM
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Joined: Jan 2003
Posts: 14,491 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
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Posts: 14,491
So. Burlington, Vt.
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In the mid-level typical bracket race engine(1.5-ish hp/ci), assuming the head/induction/exhaust are identical between the two configurations(and are appropriately sized for the desired output) I would expect the power difference to be negligible, especially if there is going to be an upper rpm limit of 7K.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Which is Faster, Bore & Stroke ?
[Re: fast68plymouth]
#2891845
02/22/21 12:40 PM
02/22/21 12:40 PM
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Joined: Jan 2003
Posts: 19,355 Las Vegas
Al_Alguire
I Live Here
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I Live Here
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Posts: 19,355
Las Vegas
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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.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Which is Faster, Bore & Stroke ?
[Re: polyspheric]
#2891848
02/22/21 12:54 PM
02/22/21 12:54 PM
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Joined: Jan 2003
Posts: 7,475 Minnesota
Hemi_Joel
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master
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Minnesota
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Same heads, cam and induction
That's the reason. Why would you keep everything the same? The bore and stroke needs to be considered when building the rest of the motor. You can use a bigger intake valve if you have a 4.5-in bore versus a 4.310 bore. Cam events would be different with a shorter stroke versus longer stroke, and the intake. That's the problem with some of these comparisons that the magazines and TV shows do. They don't build the motor around the one variable that they are testing.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Which is Faster, Bore & Stroke ?
[Re: dvw]
#2891862
02/22/21 01:36 PM
02/22/21 01:36 PM
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Joined: May 2004
Posts: 12,383 Taxes & Virus's R-US, NY
Dragula
OP
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OP
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As lon[s][/s]g as the bore doesn't restrict the size of the intake valve at the desired RPM level, it doesn't make much difference. If your combo needs more valve and it won't fit. Then it needs more bore. Doug So the bigger bore shows its an advantage right there.
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Re: Which is Faster, Bore & Stroke ?
[Re: Dragula]
#2891878
02/22/21 02:26 PM
02/22/21 02:26 PM
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Joined: Jan 2004
Posts: 8,233 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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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!
Last edited by cudaman1969; 02/22/21 02:26 PM.
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