tfreer85 Posted November 4, 2005 Share Posted November 4, 2005 Okay I'm trying to figure out the displacement of a destroked engine. Stock these are the specs: Bore x Stroke = 93x82.7 mm Rod Length =147 mm Now I know that this is a 4.5L 274CI V8 motor. I know the formula for displacement is Bore^2 x Stroke x 0.7854 x number of cylinders. And for swept volume it is (bore/2) x (bore/2) x Stroke x pi. What I'm wondering is if i change the rod length to say 140 mm how do I calculate the new displacement? And what formula would I use?? On a side note though I doubt its possible but would you be able to mate a Crank diameter of 55mm to a Rod big end of 53 mm. I know you can bore/hone out the rod but it seems like it would weaken the strength of the rod significantly and I don't think its wise to remove 2mm. Also would it be an option to grind down the crank that 2mm's or would you run into the same problem of really weak and not really practical? Thanks for the help. Tyson Quote Link to comment Share on other sites More sharing options...
tfreer85 Posted November 4, 2005 Author Share Posted November 4, 2005 Okay well the the displacement won't change, so scratch that. I guess it'll just drop compression. For an engine that isn't popular and has no aftermarket cranks out there how could you drop displacement? Sleeve the cylinders dropping the bore down and go with custom pistons? Tyson Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 4, 2005 Share Posted November 4, 2005 I think that the stroke would get +7mm of travel according to your proposed 140mm rods... This would up the displacement, and lower compression unless heads were changed. That is assuming you want to keep the same crank. But to destroke i am under the impression that you would want to get a crank with less travel/radius and then match it to longer rods to keep the compression sane but also lower stroke. Quote Link to comment Share on other sites More sharing options...
tfreer85 Posted November 4, 2005 Author Share Posted November 4, 2005 How exactly would that increase displacement? Going from a longer rod to a shorter rod? I figured it'd drop compression, but like i said there aren't any aftermarket cranks that i know of, unless you know of one for the VH45DE. Tyson Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 4, 2005 Share Posted November 4, 2005 How exactly would that increase displacement? Going from a longer rod to a shorter rod? I figured it'd drop compression' date=' but like i said there aren't any aftermarket cranks that i know of, unless you know of one for the VH45DE. Tyson[/quote'] Because it wouldn't. I am silly and assumed a shorter rod would increase stroke but i wasn't thinking Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted November 4, 2005 Share Posted November 4, 2005 What are you trying to accomplish? Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 4, 2005 Share Posted November 4, 2005 What are you trying to accomplish? I would assume higher revs? Quote Link to comment Share on other sites More sharing options...
tfreer85 Posted November 4, 2005 Author Share Posted November 4, 2005 Just looking into different engine variations of Small Liter V8's, and forgot the only way to drop displacement was to change the stroke (crank) or have a smaller bore. Tyson Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.