Lt80 stroker crank
Sep 2, 2004 | 11:30 AM
#21
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Lt80 stroker crank
asfasasu3, dont confuse a long rod motor with a stroker. You can use a long rod with a stock stroke. The piston pin is relocated to keep the piston height correct. When going long rod, in most cases, it is helpful in 2 ways. The rod angle is improved and the side loading of the piston is actually reduced becasue the pin is farther up in the piston. That frees up power. The second big thing is that your dwell of the piston (how long it stays at the top of the comression stroke) is increased by a fraction of a second and promotes better combustion and power. Hope this helps,Bubba
Bubba, I understand the longer rod desire. I've been around long rod and stroker motors in drag cars for years. The rod length does effect dwell. But in most cases not enough to tell even on a dyno. The biggest reason for running longer rods in those motors is to reduce the angle of the rod and reduce side friction that it creates on the piston. (and it also adds alot to the strength of the rod) Kinda like the knife edging. It helps in motors when the rods have to "cut" through the oil in the pan. (although alot of top builders don't like to use rods like that, they would rather use crank scrapers) The dwell is most effected by the stroke, not the rod length. I'm sure rod length can come into play some, but from what I've seen from professional engine builders is, its not enough to really factor in. (maybe in NASCAR where every 100th counts) I've had to study camshaft design in school, and if I remeber right. The larger the base circle the longer the dwell at bot tdc and bdc. The reaction of the piston will slow down as the stroke increases, meaning, as it reaches the top, the slower the piston will move. This also happens at the bottom, in which in the case of this 2 stroke, will hold the ports open alot longer. Looks like just changeing the stoke would result in about the same thing as raising the ports and making them wider. (wider coming from holding the open longer)
Bubba, I understand the longer rod desire. I've been around long rod and stroker motors in drag cars for years. The rod length does effect dwell. But in most cases not enough to tell even on a dyno. The biggest reason for running longer rods in those motors is to reduce the angle of the rod and reduce side friction that it creates on the piston. (and it also adds alot to the strength of the rod) Kinda like the knife edging. It helps in motors when the rods have to "cut" through the oil in the pan. (although alot of top builders don't like to use rods like that, they would rather use crank scrapers) The dwell is most effected by the stroke, not the rod length. I'm sure rod length can come into play some, but from what I've seen from professional engine builders is, its not enough to really factor in. (maybe in NASCAR where every 100th counts) I've had to study camshaft design in school, and if I remeber right. The larger the base circle the longer the dwell at bot tdc and bdc. The reaction of the piston will slow down as the stroke increases, meaning, as it reaches the top, the slower the piston will move. This also happens at the bottom, in which in the case of this 2 stroke, will hold the ports open alot longer. Looks like just changeing the stoke would result in about the same thing as raising the ports and making them wider. (wider coming from holding the open longer)
Sep 2, 2004 | 12:53 PM
#22
Trailblazer
Joined: Jul 2004
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Lt80 stroker crank
I know I'm way over my head in this thread but I've got a question? asfasasu, would the geometry of the V-8 engine design have anything to do with the "rod design/piston sidewall friction" question? I didn't know if a piston positioned directly over the crank would have different characteristics than that of one in a V block.
Bill
Bill
Sep 2, 2004 | 01:28 PM
#23
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Lt80 stroker crank
Bill, I don't claim to know alot about this either, but I am a draftsman by trade. And if you really think about it. The crank turns in a circle. So the centerline of the bore is lined up with the center line of the crank. No matter at what angle the "V" is, it will be directly above the crank. The reasons for making it a "v" is to shorten the overall length of the motor.
Sep 2, 2004 | 02:11 PM
#24
Extreme Pro Rider
Joined: May 2002
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Lt80 stroker crank
Originally posted by: asfasasu3
asfasasu3, dont confuse a long rod motor with a stroker. You can use a long rod with a stock stroke. The piston pin is relocated to keep the piston height correct. When going long rod, in most cases, it is helpful in 2 ways. The rod angle is improved and the side loading of the piston is actually reduced becasue the pin is farther up in the piston. That frees up power. The second big thing is that your dwell of the piston (how long it stays at the top of the comression stroke) is increased by a fraction of a second and promotes better combustion and power. Hope this helps,Bubba
Bubba, I understand the longer rod desire. I've been around long rod and stroker motors in drag cars for years. The rod length does effect dwell. But in most cases not enough to tell even on a dyno. The biggest reason for running longer rods in those motors is to reduce the angle of the rod and reduce side friction that it creates on the piston. (and it also adds alot to the strength of the rod) Kinda like the knife edging. It helps in motors when the rods have to "cut" through the oil in the pan. (although alot of top builders don't like to use rods like that, they would rather use crank scrapers) The dwell is most effected by the stroke, not the rod length. I'm sure rod length can come into play some, but from what I've seen from professional engine builders is, its not enough to really factor in. (maybe in NASCAR where every 100th counts) I've had to study camshaft design in school, and if I remeber right. The larger the base circle the longer the dwell at bot tdc and bdc. The reaction of the piston will slow down as the stroke increases, meaning, as it reaches the top, the slower the piston will move. This also happens at the bottom, in which in the case of this 2 stroke, will hold the ports open alot longer. Looks like just changeing the stoke would result in about the same thing as raising the ports and making them wider. (wider coming from holding the open longer)
asfasasu3, dont confuse a long rod motor with a stroker. You can use a long rod with a stock stroke. The piston pin is relocated to keep the piston height correct. When going long rod, in most cases, it is helpful in 2 ways. The rod angle is improved and the side loading of the piston is actually reduced becasue the pin is farther up in the piston. That frees up power. The second big thing is that your dwell of the piston (how long it stays at the top of the comression stroke) is increased by a fraction of a second and promotes better combustion and power. Hope this helps,Bubba
Bubba, I understand the longer rod desire. I've been around long rod and stroker motors in drag cars for years. The rod length does effect dwell. But in most cases not enough to tell even on a dyno. The biggest reason for running longer rods in those motors is to reduce the angle of the rod and reduce side friction that it creates on the piston. (and it also adds alot to the strength of the rod) Kinda like the knife edging. It helps in motors when the rods have to "cut" through the oil in the pan. (although alot of top builders don't like to use rods like that, they would rather use crank scrapers) The dwell is most effected by the stroke, not the rod length. I'm sure rod length can come into play some, but from what I've seen from professional engine builders is, its not enough to really factor in. (maybe in NASCAR where every 100th counts) I've had to study camshaft design in school, and if I remeber right. The larger the base circle the longer the dwell at bot tdc and bdc. The reaction of the piston will slow down as the stroke increases, meaning, as it reaches the top, the slower the piston will move. This also happens at the bottom, in which in the case of this 2 stroke, will hold the ports open alot longer. Looks like just changeing the stoke would result in about the same thing as raising the ports and making them wider. (wider coming from holding the open longer)
Sep 2, 2004 | 02:30 PM
#25
Trailblazer
Joined: Jul 2004
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Lt80 stroker crank
I see what your saying. The only force that would affect it would be gravity.(The weight of the piston laying against the cylinder wall) That would really be nitpicking - wouldn't it.
DStroyer, I want to know all about this little monster when you get it going.
Thanks
Bill
DStroyer, I want to know all about this little monster when you get it going.
Thanks
Bill
Sep 2, 2004 | 02:37 PM
#26
Pro Rider
Joined: Sep 2003
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Lt80 stroker crank
I"m with ya Bubba!!! And I really appreciate (had to look that one up) what these guys are doing. My hats off to them and all like them. I have kinda made our LT a hobbie in progress. I read everthing I can about these things and have tried alot of them. I'm a gear head at heart, but I don't have the funds, time or equipment to tackle some of this stuff. (although thers not much I wouldn't try) Dstroyer asked LT80 if he had resleeved any of these lately. I have done this just last month to our LT. I was waiting on parts and decided to give it a whirl so I could clean up the ports better. Is it any wonder why I ask so many questions on here? I'm always trying to put our stuff back together!!! LOL!!! Like I mentioned before, I hade to study camshaft design in mechinal drafting classes I've taken in the past. (for those wondering, crankshafts fall into this group) And this is something that really sparked my interest.
Sep 2, 2004 | 08:20 PM
#27
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Lt80 stroker crank
OK, finally got time to answer [img]i/expressions/face-icon-small-smile.gif[/img]
Flat piston: I'll take your word for it on this one. I've thought of lathing a piston flat, but I feel it would be to thin. I haven't looked into another piston that has the same pin size and location.
Head and spark plug: You will not have any trouble here.The LT80 head modded has plenty of room for the spark plug.Understand now that we allready are running a B8HIX plug instead ot the BP style. The P means protruded and is for stock, low rpm machines. It's protruded design is made to keep the plug clean.That's why their for stock/lawn mowers/etc.
I'll PM Dstroyer on how to make a head. You are correct, the squish band is very important.Some ppl think the squish band means the clearance between the piston and head, it's not. A wide squish band is better.
Compression will not change because it makes compression from the exhaust port up, and this isn't going to change because of the stroker.
Bubba's explaination of Xmm up and Xmm down is why I thought 2mm was sufficient. I feel that the only porting difference will be in lowering the transfer openings and the bottom of the exhaust port to allow the stroker to do it's thing. I point the transfers, not nessesarilly raise them. I've learned that the farther you raise the transfers(past a certain point) it makes the machine slower.A simple way to look at this is: transfers open when the piston is 1/2 way down the exhaust port.
What Dstroyer is refering to is the "exhaust scavenge" To bring in more fresh fuel mix is the objective.
As far as re-sleeving, no. I haven't seen a reason to. I have the tools needed to do my work with it in place.
Asfas,, I agree w/bubba. Your smarter than you think on all this [img]i/expressions/face-icon-small-smile.gif[/img]
Flat piston: I'll take your word for it on this one. I've thought of lathing a piston flat, but I feel it would be to thin. I haven't looked into another piston that has the same pin size and location.
Head and spark plug: You will not have any trouble here.The LT80 head modded has plenty of room for the spark plug.Understand now that we allready are running a B8HIX plug instead ot the BP style. The P means protruded and is for stock, low rpm machines. It's protruded design is made to keep the plug clean.That's why their for stock/lawn mowers/etc.
I'll PM Dstroyer on how to make a head. You are correct, the squish band is very important.Some ppl think the squish band means the clearance between the piston and head, it's not. A wide squish band is better.
Compression will not change because it makes compression from the exhaust port up, and this isn't going to change because of the stroker.
Bubba's explaination of Xmm up and Xmm down is why I thought 2mm was sufficient. I feel that the only porting difference will be in lowering the transfer openings and the bottom of the exhaust port to allow the stroker to do it's thing. I point the transfers, not nessesarilly raise them. I've learned that the farther you raise the transfers(past a certain point) it makes the machine slower.A simple way to look at this is: transfers open when the piston is 1/2 way down the exhaust port.
What Dstroyer is refering to is the "exhaust scavenge" To bring in more fresh fuel mix is the objective.
As far as re-sleeving, no. I haven't seen a reason to. I have the tools needed to do my work with it in place.
Asfas,, I agree w/bubba. Your smarter than you think on all this [img]i/expressions/face-icon-small-smile.gif[/img]
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