Post by hydroli on Aug 1, 2008 20:05:33 GMT -5
I've been told that going over .200 of added stroke can be tricky. What does limits the stroke on the chevette engine is the short deck height from what I've learned. It measures only 198mm.
** I can't tell if the rod will hit the block or cylinder since I don't have the block in front of me. Although, these can be avoid by grinding the casting that it hits. The following content is true regardless of these elements**
A few things are to be considered before building a setup.
Rod to stroke ratio:
From different sources, the minimum rod to stroke ratio should not go under 1.5:1 as the maximum is 2:1.
For example, a chevy 400ci small block will have a short rod 5.565 with a long stroke, 3.750, which gives a 1.48:1 rod to stroke ratio.
Referring to the strokerengine.com website, the 400ci will work well in its stock combination but will vibrate over 5500rpm. Changing the rod with a longer one, a 5.700" as from the 350ci chevy, will let it rev over 6000rpm without a problem. This change make the rod/stroke ratio pass from 1.48 to 1.52.
I have to stay above 1.5:1 rod to stroke ratio. Over this, the engine will run out of breath at high speeds, over 5500rpm. Some Honda engines will have a stock rod to stroke ratio of 1.75:1, which is a compromise and that will make it a drivable and high reving engine.
Links:
www.strokerengine.com/RodStroke.html
www.hondatuningmagazine.com/tech/0506_ht_rod_stroke_ratio/index.html
en.wikipedia.org/wiki/Otto_cycle#The_Otto_cycle
Mean piston speed and piston acceleration:
Another thing that physical laws won't give us is the piston speed factor. Exceeding it will result in excessive friction and premature wear.
The value that has to be verified is the mean piston speed which is an approximative value. It will give an idea of the average speed the piston travels from the bottom to the top at a given rpm value and thereby, an idea of the forces applied to the crank journals.
However, this parameter won't consider the piston acceleration which is greater as the rod to stroke ration is smaller. This is one of the reasons why a higher rod to stroke ratio should be favored.
yarchive.net/metal/piston_acceleration.html
*** I dont have time now to finish this article and can't tell if I'll finish it soon or ever, sorry to anyone interested in the subject. ***
** I can't tell if the rod will hit the block or cylinder since I don't have the block in front of me. Although, these can be avoid by grinding the casting that it hits. The following content is true regardless of these elements**
A few things are to be considered before building a setup.
Rod to stroke ratio:
From different sources, the minimum rod to stroke ratio should not go under 1.5:1 as the maximum is 2:1.
For example, a chevy 400ci small block will have a short rod 5.565 with a long stroke, 3.750, which gives a 1.48:1 rod to stroke ratio.
5.565/3.750 = 1.484/1
Referring to the strokerengine.com website, the 400ci will work well in its stock combination but will vibrate over 5500rpm. Changing the rod with a longer one, a 5.700" as from the 350ci chevy, will let it rev over 6000rpm without a problem. This change make the rod/stroke ratio pass from 1.48 to 1.52.
5.700/3.750 = 1.52
I have to stay above 1.5:1 rod to stroke ratio. Over this, the engine will run out of breath at high speeds, over 5500rpm. Some Honda engines will have a stock rod to stroke ratio of 1.75:1, which is a compromise and that will make it a drivable and high reving engine.
Links:
www.strokerengine.com/RodStroke.html
www.hondatuningmagazine.com/tech/0506_ht_rod_stroke_ratio/index.html
en.wikipedia.org/wiki/Otto_cycle#The_Otto_cycle
Mean piston speed and piston acceleration:
Another thing that physical laws won't give us is the piston speed factor. Exceeding it will result in excessive friction and premature wear.
The value that has to be verified is the mean piston speed which is an approximative value. It will give an idea of the average speed the piston travels from the bottom to the top at a given rpm value and thereby, an idea of the forces applied to the crank journals.
However, this parameter won't consider the piston acceleration which is greater as the rod to stroke ration is smaller. This is one of the reasons why a higher rod to stroke ratio should be favored.
yarchive.net/metal/piston_acceleration.html
*** I dont have time now to finish this article and can't tell if I'll finish it soon or ever, sorry to anyone interested in the subject. ***
