Bore Vs. Stroke...... - Chevelle Tech
Chevelle Tech join team chevelle as a supporting member  
Chevelle Parts at      
GROUND UP &         
Official Sponsor of Team Chevelle

Auto Insurance is the premier Chevrolet Chevelle Forum on the internet. Registered Users do not see the above ads.
1999 -- Tech Files - reference area
1000's of previous topics

Thread Tools Search this Thread Display Modes
Old Feb 18th, 00, 3:24 PM
Horsepower69 Horsepower69 is offline
Join Date: Feb 2000
Posts: 17

Is it true that an engine with a big bore and short stroke will produce more horsepower than torque?? Will an engine with small bore but long stroke produce more torque?? My last question is: will an engine with a big bore and long stroke produce good torque and horsepower??


Quick reply to this message
Sponsored Links
Old Feb 18th, 00, 9:04 PM
IgnitionMan IgnitionMan is offline
Senior Tech Team
Join Date: Nov 1999
Location: Whittier, California
Posts: 330

Quick reply to this message
Old Feb 18th, 00, 9:21 PM
DZAUTO DZAUTO is offline
Team Member
Join Date: Sep 1998
Location: Mustang, OK USA
Posts: 11,078

Ditto. You catch on quick.

Tom Parsons
Quick reply to this message
Old Feb 20th, 00, 2:27 AM
robzr robzr is offline
Join Date: Dec 1999
Location: Chicago, IL US of A
Posts: 11

bore:stroke ratio is something that I'd like
to discuss, hopefully some people out there
are willing... here's some tidbits of
knowledge that I can share with ya:

When bore is greater than stroke, the engine
is called oversquare I think. I guess that
means a large stroke engine is undersquare?

One important factor is that a large bore
engine will have greater area for the valves
than the same displacement engine with a
larger stroke. Large valves (in relation to
displacement) are better for higher rpm power.

A shorter stroke means less distance for the
piston to cover with each revolution, there
fore the pistons velocity, and hence
acceleration is lower than that of a large
stroke motor. Less acceleration means less
force (stress) on the rotating assembly, so
the motor can safely rev higher. However,
force = mass * acceleration, and a larger
bore motor will have heavier pistons. I'm
guessing that this still works out in favor
of the large bore engine, though, as large
bore engines can rev higher.

I think the only other factor that could come
into play here would be the actual motion of
the piston/rod. Longer stroke motors will
have a lower rod:stroke ratio. However I
believe that a higher rod:stroke ratio is
better for power throughout the rpm range,
so it would seem like the large bore engine
wins out here.



Quick reply to this message
Old Feb 20th, 00, 4:30 AM
Gene Chas Gene Chas is offline
Senior Tech Team
Join Date: Apr 1999
Location: Buffalo, NY
Posts: 1,525

And small bore/long stroke combinations can handle more compression than big bore/short stroke combinations.

Gold #62/ACES
67 SS396/L88
Quick reply to this message
Old Feb 20th, 00, 11:00 PM
Schurkey Schurkey is offline
Gold Founding Member
Join Date: Aug 1998
Location: the Seasonally Frozen Wastelands
Posts: 10,174

Within the general limits of production V-8 car engines produced from WWII to about 1995 or so, I think that Bore/Stroke ratio is overemphasized.

Look at the difference between Buick 455 and Olds 455 engines:

Buick has 4.32 bore and 3.9 stroke. Big bore, short stroke. Very oversquare.
Olds has 4.125 bore and 4.250 stroke. Small bore, long stroke. Very undersquare.

The Buick should be a high rpm screamer, and the Olds could go into a John Deere tractor...

Except BOTH engines are famed for low rpm grunt, and neither one will rev like a 454 Chevy.

Ford used to advertise thier 427 as being like a "race engine" because of the big bore/ short stroke.

Chevy's 427 has almost identical Bore/stroke, and Chevy stuffed them in two ton potato trucks, in addition to L-88 Corvettes.

True enough, bore/stroke makes a difference when you're talking Formula 1, Nascar, even some wild ass motorcycles (Suzuki's GSXR 750's come to mind, also Honda's oval piston wonder/nightmare.)

For all the rest of us, Carburation and manifolding is MUCH more important. Cylinder head flow capacity is MUCH more important, Combustion chamber quench and swirl is MUCH more important, reciprocating/rotating weight is more important and perhaps rod length is more important, too.

Far too many engines are blown up because the valve train was over-revved, rather than the bottom end fragging because of a long stroke.
Quick reply to this message
Old Dec 22nd, 04, 3:01 PM
wrencheadblues wrencheadblues is offline
Tech Team
Join Date: Feb 2002
Location: spokane,wa .us
Posts: 304

just what I needed to help me building my tall deck 427 trk blk - thanks let me know if you have any tall deck parts
CPE= 1930 3window coupe / Trk= 1966 elky big blk 4spd / DROPTOP=1966 SS convertible 2nd owner / 1966 drag car 427
Quick reply to this message
Old May 8th, 06, 11:22 PM
david5 david5 is offline
Join Date: May 2006
Posts: 1
Default Bore/stroke 101/73 that

I am wondering about the new BMW R1200S... The Germans made them with
Bore/stroke 101/73 that produces 122 HP at 8250rpm...

My questions is,,, if I would reduce the stroke to 56 instead of 73... what would the HP outcome...? I wonder about that....

Does anyone have an idea about the above?
I love the way the BMW R1200S looks... Great design...

I was planning on buying a SP2/RC51 but I might swith to BMW if HP works out well...

Please let me know
Quick reply to this message
Sponsored Links
Chevelle Tech > Team Chevelle > Archives > 1999 --      Current Topic: Bore Vs. Stroke......
Quick Reply

Register Now

In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.
Email Address:
You do not have to be specific but it helps others answer your questions or offer parts.
Please select your insurance company (Optional)
First Name
It's always nice to know a name instead of Mrhot67ss
One last thing to do to slow down the spammers
Enter the first letter of this word: Chevelle


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -4. The time now is 1:18 AM.

Is there a site like this for?    El Caminos Camaros Novas Impalas GTO Chevy Punch All Chevys

2009 Team Chevelle - AutoForums