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Pistons
While I've got you guys all riled up, I thought I'd talk about pistons. My cylinders have about .008 or .009 inches of taper in them. At the bottom, where the iron stays cooler, the cylinders are hardly worn at all. At the top, near the combustion chamber, there is measurable wear. This is what you expect, and what you normally see when you take an old motor apart. If I was just building a restored bike for shows that only had to start and run for a few minutes at a time to prove that it could, I would use the cylinders as they are, without boring them out, and I would use the existing pistons. Since this bike is going to be a rider, .008 to .009 inches of taper is too much. Like a coat hanger, you can only bend piston rings so many times before they break.
The original Indian pistons are made of cast iron. Not commonly used for pistons today, but perfectly adequate for the stress levels that this engine sees. It's a thousand cc engine that makes about fifteen horsepower. The compression ratio is something like six and a half to one. The stresses in this engine are on the order of the stresses that an old Briggs and Stratton lawn mower engine would see. If I could find old oversized Indian pistons, I would use them, but I have not been able to find any. So, I began to look for custom piston manufacturers. There are several of them out there; such as Venolia, J&P, Egge, Arias, Wiseco, Ross, and more. I contacted all of those and several more, described the Indian Powerplus pistons, and asked whether they could make me some pistons that would work. Several of them said that they would be able to make me pistons, so it was just down to my judgement who I went with. After a bit of discussion, I made a deal with Nick Arias III to make me some pistons.
The pistons will be made of forged aluminum. I think cast aluminum Pistons would have been fine, because I've had engines with half the displacement that make twice the horspower and run at twice to RPMs with cast aluminum pistons. I'm not saying forged pistons aren't better, I'm just saying that I think cast pistons would have been good enough. That being said, most of the custom piston manufacturers are making forged pistons now, since their main market is making pistons for racing engines. So it will have forged pistons. I'll need to adjust the clearance appropriately, since forged aluminum pistons need a little more clearance. They expand faster than the cast iron barrels, so you have to give them enough clearance that they don't sieze. They'll rattle and slap a little when cold, but that doesn't hurt anything.
The pistons will look more like modern pistons. They'll be cam ground, and they won't be full skirted like the old ones. They'll have 5/8 inch pins like the old ones, but the bushings will need to be shortened a bit because the aluminum Pistons need a heavier pin boss, so the boss to boss dimension will be shorter. Arias is supplying the pins, which they're getting them from Egge and then they'll grind them to the proper length.
Thats enough info for now, I think I'll save the subject of piston rings for the next discussion. I hope to hear your thoughts on pistons.
Kevin
.
While I've got you guys all riled up, I thought I'd talk about pistons. My cylinders have about .008 or .009 inches of taper in them. At the bottom, where the iron stays cooler, the cylinders are hardly worn at all. At the top, near the combustion chamber, there is measurable wear. This is what you expect, and what you normally see when you take an old motor apart. If I was just building a restored bike for shows that only had to start and run for a few minutes at a time to prove that it could, I would use the cylinders as they are, without boring them out, and I would use the existing pistons. Since this bike is going to be a rider, .008 to .009 inches of taper is too much. Like a coat hanger, you can only bend piston rings so many times before they break.
The original Indian pistons are made of cast iron. Not commonly used for pistons today, but perfectly adequate for the stress levels that this engine sees. It's a thousand cc engine that makes about fifteen horsepower. The compression ratio is something like six and a half to one. The stresses in this engine are on the order of the stresses that an old Briggs and Stratton lawn mower engine would see. If I could find old oversized Indian pistons, I would use them, but I have not been able to find any. So, I began to look for custom piston manufacturers. There are several of them out there; such as Venolia, J&P, Egge, Arias, Wiseco, Ross, and more. I contacted all of those and several more, described the Indian Powerplus pistons, and asked whether they could make me some pistons that would work. Several of them said that they would be able to make me pistons, so it was just down to my judgement who I went with. After a bit of discussion, I made a deal with Nick Arias III to make me some pistons.
The pistons will be made of forged aluminum. I think cast aluminum Pistons would have been fine, because I've had engines with half the displacement that make twice the horspower and run at twice to RPMs with cast aluminum pistons. I'm not saying forged pistons aren't better, I'm just saying that I think cast pistons would have been good enough. That being said, most of the custom piston manufacturers are making forged pistons now, since their main market is making pistons for racing engines. So it will have forged pistons. I'll need to adjust the clearance appropriately, since forged aluminum pistons need a little more clearance. They expand faster than the cast iron barrels, so you have to give them enough clearance that they don't sieze. They'll rattle and slap a little when cold, but that doesn't hurt anything.
The pistons will look more like modern pistons. They'll be cam ground, and they won't be full skirted like the old ones. They'll have 5/8 inch pins like the old ones, but the bushings will need to be shortened a bit because the aluminum Pistons need a heavier pin boss, so the boss to boss dimension will be shorter. Arias is supplying the pins, which they're getting them from Egge and then they'll grind them to the proper length.
Thats enough info for now, I think I'll save the subject of piston rings for the next discussion. I hope to hear your thoughts on pistons.
Kevin
.
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