- Joined
- Dec 10, 2008
- Messages
- 7,253
It is obvious from your picture that you have two pistons that were produced at much different times and the casting mold had been renewed. That is why the weight is different. Trade them in or grind off the weight to match them. Personally I would send them back for another pair.
JCC / Emgo pistons are by no means an inferior piston. They are standard equipment pistons in Subaru, many Yamahas and have been used by top engine builders for years.
When you are considering a cast vs a forged piston keep in mind the facts.
1. Cast pistons are harder metal . That means they will wear longer on the skirts, pin bores and ring lands.
2. Since they are hard they are more brittle, they can crack and break up if they are subject to detonation.
3. Cast pistons do not grow as much as forged pistons, Therefore they can be fit with less clearance for better oil control and faster heat transfer to the barrel.
4. Forged pistons are soft and ductile. That means they will handle detonation without breaking up but detonation will cause the piston to get hot rapidly which means they will grow more in size and may seize -particularly in a cast iron bore.
5. Each piston has it's good points and bad points. For long life on a regular street motor you will get longer service with a cast piston. I have also road raced very successfully using cast pistons.
6. For pushing an engine to it's limit when racing or running extreme compression or a blower then a forged piston may be the right choice.
7. Forged pistons can be made up in nearly any configuration since they are machined to the needs from a standard forged slug.
8. Cast pistons require a dedicated casting mold which is very expensive and can only be justified for large production numbers. Therefore they are made to a standard configuration since that is where the sales numbers will be highest.
I wish I could run a cast piston in my injected bike. Unfortunately I have not found a suitable piston to fill my needs. But I do have my eye on a possibility. Jim
JCC / Emgo pistons are by no means an inferior piston. They are standard equipment pistons in Subaru, many Yamahas and have been used by top engine builders for years.
When you are considering a cast vs a forged piston keep in mind the facts.
1. Cast pistons are harder metal . That means they will wear longer on the skirts, pin bores and ring lands.
2. Since they are hard they are more brittle, they can crack and break up if they are subject to detonation.
3. Cast pistons do not grow as much as forged pistons, Therefore they can be fit with less clearance for better oil control and faster heat transfer to the barrel.
4. Forged pistons are soft and ductile. That means they will handle detonation without breaking up but detonation will cause the piston to get hot rapidly which means they will grow more in size and may seize -particularly in a cast iron bore.
5. Each piston has it's good points and bad points. For long life on a regular street motor you will get longer service with a cast piston. I have also road raced very successfully using cast pistons.
6. For pushing an engine to it's limit when racing or running extreme compression or a blower then a forged piston may be the right choice.
7. Forged pistons can be made up in nearly any configuration since they are machined to the needs from a standard forged slug.
8. Cast pistons require a dedicated casting mold which is very expensive and can only be justified for large production numbers. Therefore they are made to a standard configuration since that is where the sales numbers will be highest.
I wish I could run a cast piston in my injected bike. Unfortunately I have not found a suitable piston to fill my needs. But I do have my eye on a possibility. Jim
