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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Oct 2012 Posts: 57 Shop Shark | | Shop Shark Joined: Oct 2012 Posts: 57 | how many cubic inches i will have on a 261 with a 848 head and a .060 overbore... i am getting a headache trying to figure it out..:) | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Around 270 ci is my recollection. I think I calculated this 39 years ago when I rebuilt my 261 0.060 over-bored. Here are bore and stroke measurements. Here is a calculator. I'll calculate it, if you don't, after the movie I am watching is over. | | | | | Joined: Feb 2004 Posts: 29,798 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,798 |
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 |
Thanks, Jerry, my worn out memory is sometimes right.
Is the factory calculated displacement just the cylinder bore x stroke height, or does it include the entire combustion chamber (including the head portion of the combustion chamber)?
| | | | | Joined: Feb 2004 Posts: 29,798 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,798 | Piston displacement is simply the air volume that moves through the engine when the crankshaft makes 2 turns. Compression ratio calculations involve figuring in combustion chamber volume, deck clearance, head gasket volume, etc. Then there's that nasty one, volumetric efficiency, where port shape and volume, valve lift and duration, and all those other variables have to be considered. Around 90% VE is a pretty good rule of thumb for a somewhat stock stovebolt engine.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Aug 2013 Posts: 568 Shop Shark | | Shop Shark Joined: Aug 2013 Posts: 568 | Wallaceracing.com has a ton of calculators that are darn accurate for figuring out what ya got. Darn near matched my dyno sheet and head flow numbers.
Last edited by Hollow65; 06/14/2014 7:05 AM.
I can explain it to you, I can't understand it for you.
| | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | The accepted rationale for swept volume (rather than total volume) is that at the end of the exhaust stroke the chamber is not completely purged of combustion byproducts.
Yes, that does give an interesting advantage to a low compression ratio engine with some method of purging the chamber - such as tuned exhaust and/or a supercharger. | | | | | Joined: Feb 2014 Posts: 46 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2014 Posts: 46 | true on supercharger,im thinkin more about properly placed turbo.far enough away from motor so air is as cool going into motor as it would have been stock but under presure.i seen article where guy put turbos above rear axle in car to produce these results | | | | | Joined: Feb 2014 Posts: 215 Shop Shark | | Shop Shark Joined: Feb 2014 Posts: 215 | A "properly placed" turbocharger will be as close to the manifold as possible to make use of the thermal energy. That hot gas has a much higher volume that the cool gas would have back at the axle, thus spinning the turbo faster....not to mention line loss of all the redundant plumbing needed. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 |
whiskey runner,
Have these posts helped, or do you now have a worse headache?
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