Figuring engine displacement - Chevy Impala SS Forum
Impala SS Forum
Go Back   Chevy Impala SS Forum > General Topics > Misc.
New User? Register - Forgot Password

Reply
 
Thread Tools Display Modes
  #1  
Old 01-09-2010, 10:52 PM
95BRMW's Avatar
95BRMW 95BRMW is offline
Senior Member
 
Join Date: Mar 2008
Location: CT
Posts: 1,438
95BRMW is on a distinguished road
Default Figuring engine displacement

Something that I have been wondering or a while, how do figure out the displacement of an engine that was bored out? About 10 years ago my father and I rebuilt the engine in our 87 lesabre (don't laugh, it was an excellent learning experience). We attempted to hone it out ourselves but screwed it up and and had a shop bore it out to fix what we did. The engine is a 231ci 3.8l V6 bored out 20 over (going by the receipt from the shop that I manged to keep).
So what size is this engine now? And did we gain any HP or anything good from this?
__________________
1995 DCM Roadmaster Wagon 106K
1995 LDM 1A2 Caprice Wagon 202K
1994 9C1 Caprice 145k
1996 Black/Black FWB 170k
1975 Impala Coupe
1997 Riviera Supercharged
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 01-09-2010, 11:34 PM
sharkx's Avatar
sharkx sharkx is offline
Senior Member
 
Join Date: Nov 2007
Location: Cleveland
Posts: 435
sharkx is on a distinguished road
Default

Volume of one cylinder = Pi x 2R x S

Where Pi equals 3.1412
R is this the radius of the engine times 2
and S equals the stroke

Multiply the volume times the number of cylinders and you have the total displacement.

There are lots of online calculators that can do this for you.

Without knowing the stroke, I can't say for sure but you probably picked up 2 or 3 cubic inches.

Sharkx
__________________
Educatio est omnium efficacissima forma rebellionis
Reply With Quote Quick reply to this message
  #3  
Old 01-10-2010, 12:12 AM
fbi9c1 fbi9c1 is offline
Senior Member
 
Join Date: Jul 2005
Location: Los Angeles
Posts: 3,013
fbi9c1 is an unknown quantity at this point
Default

Pi = 3.1416
__________________
Jim B.

'95 9c1, pcmperformance.com 93 tune, Dynomax Ultraflo catback, K & N box filter, LT4 KM, 160 stat, 3.08 Posi.
Reply With Quote Quick reply to this message
  #4  
Old 01-10-2010, 05:06 AM
Navy Lifer's Avatar
Navy Lifer Navy Lifer is online now
Senior Member
 
Join Date: Nov 2000
Location: Canton GA
Posts: 6,027
Navy Lifer is an unknown quantity at this point
Default

Wiki specs

The bore was enlarged to 3.8 in (96.5 mm), identical to the Buick 350 and Olds 307 V8s, yielding 231 cu in (3.8 L) displacement.

bore of 3.80" and a stroke of 3.40"

larger 252 cu in (4.1 L) version of the 3.8 L LD5 V6 was produced from 1980 through 1984 and marketed as an alternative to a V8. The bore was enlarged to 3.965 in (100.71 mm)

For your 3.8 rebuild:

New bore 3.820"

R = 1.91"

R x R = 3.6481

3.6481 x 3.14159 = 11.46083" area of cylinder bore

S = 3.4"

38.96683 cubic inches volume per cylinder

233.8 CI total

Try "running the numbers" for the original published dispalcement (231), which is often rounded up or down from a true calculated displacement--see what it actually measures to know the real difference from boring the cylinders .020". Use bore 3.80 and stroke 3.4

Since the engine was bored, can we assume that new pistons were used?

The amount of increase in displacement by itself would have minimal effect on power output--MAYBE a couple of HP.
__________________
Bill Harper
ISSCA #127
inov8r@windstream.net
Reply With Quote Quick reply to this message
  #5  
Old 01-10-2010, 10:11 AM
95BRMW's Avatar
95BRMW 95BRMW is offline
Senior Member
 
Join Date: Mar 2008
Location: CT
Posts: 1,438
95BRMW is on a distinguished road
Default

Cool, thanks for the info guys. And yes, new pistons were installed.
__________________
1995 DCM Roadmaster Wagon 106K
1995 LDM 1A2 Caprice Wagon 202K
1994 9C1 Caprice 145k
1996 Black/Black FWB 170k
1975 Impala Coupe
1997 Riviera Supercharged
Reply With Quote Quick reply to this message
  #6  
Old 01-10-2010, 12:57 PM
CCRider CCRider is offline
Senior Member
 
Join Date: Mar 2008
Posts: 253
CCRider is on a distinguished road
Default

This is easy to remember......
Bore x bore x .7854 x stroke x # of cylinders
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy Impala SS Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

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
Display Modes

Posting Rules
You may post new threads
You may 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 -5. The time now is 06:14 PM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.
(c) 2007-2014 Impala SS Forum