Keller
Enthusiast
In what model yr did they change the cams to a smoother grind and the piston to cast units?
What Yr. did they change,,,,
- Thread starter Keller
- Start date
2BADD 4U
Enthusiast
1999
In 1999, Chrysler deemed it necessary to change the pistons due to several reasons. Most were the escalating transmission complaints and the quick to replace a tranny dealers who were scamming the factory for new trannys.
Another reason was emissions, but not entirely. The actual emission output is exactly the same as it was in 1997. In some cases it is worse.
The newer pistons are different as well as the rods. The different parts will not interchange between years. With the lumpy cam you could run a much stronger forged piston and have lotsa torque. It also worked very well at higher piston speeds. The offset of this was greater thermal expansion and skirt slap. When you soften a camshaft and everyone wants power, you have to find it elsewhere. The intake was already close to max effiency and the heads could not be modified without having to recertify the engine. The only other change that could be made was to change the piston design.
What is different is that the hyperpathetic pistons are a high silicon content design. With this they are thermally stronger to a small window. This allows a closer piston to wall clearance which leads itself to less blowby, lower tension rings, and reduced emissions. In addition to this, Chrysler engineers wanted to be sure that they kept the power levels up so the wrist pin weight was changed. You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
The drawback is that once the peak thermal limit has been reached for a hyperpathetic piston, it flakes or cracks away. It literally self destructs. It will not hold its heat treating and will shatter like glass. Forged pistons will hold their structure, yet will actually melt at much higher temps due to the slow annealing process in their heat treating. This is why forged pistons are the ones of choice for all big nitrous and forced induction applications.
What can be done? You can ceramic coat the Creampuff slugs and forget the problems, or buy a $1000.00 worth of new forged pistons. Ceramic coating costs about $500.00 and is worth gold plating. Ford now supplies ALL its new 4.6 and 5.4 engines with ceramic coated pistons. They do this to reduce all scuffing and to eliminate all possible piston failures with their forced induction systems.
In 1999, Chrysler deemed it necessary to change the pistons due to several reasons. Most were the escalating transmission complaints and the quick to replace a tranny dealers who were scamming the factory for new trannys.
Another reason was emissions, but not entirely. The actual emission output is exactly the same as it was in 1997. In some cases it is worse.
The newer pistons are different as well as the rods. The different parts will not interchange between years. With the lumpy cam you could run a much stronger forged piston and have lotsa torque. It also worked very well at higher piston speeds. The offset of this was greater thermal expansion and skirt slap. When you soften a camshaft and everyone wants power, you have to find it elsewhere. The intake was already close to max effiency and the heads could not be modified without having to recertify the engine. The only other change that could be made was to change the piston design.
What is different is that the hyperpathetic pistons are a high silicon content design. With this they are thermally stronger to a small window. This allows a closer piston to wall clearance which leads itself to less blowby, lower tension rings, and reduced emissions. In addition to this, Chrysler engineers wanted to be sure that they kept the power levels up so the wrist pin weight was changed. You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
The drawback is that once the peak thermal limit has been reached for a hyperpathetic piston, it flakes or cracks away. It literally self destructs. It will not hold its heat treating and will shatter like glass. Forged pistons will hold their structure, yet will actually melt at much higher temps due to the slow annealing process in their heat treating. This is why forged pistons are the ones of choice for all big nitrous and forced induction applications.
What can be done? You can ceramic coat the Creampuff slugs and forget the problems, or buy a $1000.00 worth of new forged pistons. Ceramic coating costs about $500.00 and is worth gold plating. Ford now supplies ALL its new 4.6 and 5.4 engines with ceramic coated pistons. They do this to reduce all scuffing and to eliminate all possible piston failures with their forced induction systems.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Ford now supplies ALL its new 4.6 and 5.4 engines with ceramic coated pistons. They do this to reduce all scuffing and to eliminate all possible piston failures with their forced induction systems.<HR></BLOCKQUOTE>
2BADD, you certainly sound knowledgeable, but I'm wondering about this statement. As far as I know, Ford uses forged pistons in all its engines equipped with forced induction (the Lightning and the '03 Cobra come to mind). Are you saying the pistons are both forged and ceramic coated? And if they are, that doesn't seem to support the notion that ceramic coated hypereutectics are so durable.
Ronnie
2BADD, you certainly sound knowledgeable, but I'm wondering about this statement. As far as I know, Ford uses forged pistons in all its engines equipped with forced induction (the Lightning and the '03 Cobra come to mind). Are you saying the pistons are both forged and ceramic coated? And if they are, that doesn't seem to support the notion that ceramic coated hypereutectics are so durable.
Ronnie
1999 Vipers had forged pistons...2000-2002 Vipers had cast pistons.
racetech
Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2BADD 4U:
1999
You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
<HR></BLOCKQUOTE>
This is always fascinating to me--the notion that rod length has a significant impact on piston "dwell". It is so engrained into the psyche of engine builders all over. I used to believe it myself. Heck, it's in "all" the books, right? Smokey, Grumpy...
But...sorry. Time for the truth.
My buddies at RM tested this "piston dwell" idea. They had been testing engine combinations with various rod lengths and found that the torque & hp curves were essentially identical. There's a good reason for that. Rod length (rod ratio) does NOT have hardly any influence on piston motion.
I was told to "do the math and see how close the piston motion is, regardless of how long or short the rod is". So...we did do the math. RM was right. From the longest to the shortest rod length, the difference in piston position in the critical area near TDC was negligible. .0004" @ 10° ATD (the time when the greatest pressure is exerted on the piston).
If you'd like, you can repeat a test performed in conjunction with engineers at GM Performance about 8 years ago. They had a small block Chev. racing engine built with the shortest rods that would even work...then changed only the pistons & rods to the longest rod that would fit into the block. The result? Nearly identical hp & torque curves. The reason? Because the piston motion is nearly identical regardless of the rod you use. "Piston dwell" is a figment of imagination.
So...the bottom line? Use the longest rod you can when designing an engine. It'll keep the CH (compression height) of the piston to a minimum and thus keep the pistons light. The reduced rod angularity also eases side loadings on piston skirts. Throw away your equations for rod ratio...don't waste time trying to build your engine around some magic rod ratio number. Pick the longest rod you can and make the pistons as short as possible to save reciprocating mass.
1999
You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
<HR></BLOCKQUOTE>
This is always fascinating to me--the notion that rod length has a significant impact on piston "dwell". It is so engrained into the psyche of engine builders all over. I used to believe it myself. Heck, it's in "all" the books, right? Smokey, Grumpy...
But...sorry. Time for the truth.
My buddies at RM tested this "piston dwell" idea. They had been testing engine combinations with various rod lengths and found that the torque & hp curves were essentially identical. There's a good reason for that. Rod length (rod ratio) does NOT have hardly any influence on piston motion.
I was told to "do the math and see how close the piston motion is, regardless of how long or short the rod is". So...we did do the math. RM was right. From the longest to the shortest rod length, the difference in piston position in the critical area near TDC was negligible. .0004" @ 10° ATD (the time when the greatest pressure is exerted on the piston).
If you'd like, you can repeat a test performed in conjunction with engineers at GM Performance about 8 years ago. They had a small block Chev. racing engine built with the shortest rods that would even work...then changed only the pistons & rods to the longest rod that would fit into the block. The result? Nearly identical hp & torque curves. The reason? Because the piston motion is nearly identical regardless of the rod you use. "Piston dwell" is a figment of imagination.
So...the bottom line? Use the longest rod you can when designing an engine. It'll keep the CH (compression height) of the piston to a minimum and thus keep the pistons light. The reduced rod angularity also eases side loadings on piston skirts. Throw away your equations for rod ratio...don't waste time trying to build your engine around some magic rod ratio number. Pick the longest rod you can and make the pistons as short as possible to save reciprocating mass.
genXgts
Enthusiast
true cream puff status was attained in 2000 with both softer cam and cast pistons.
99 cars had forged pistons with a softer cam profile than 96-98 cars. I think a mid way point in profile between 96-98 and 2000 and beyond. That's my understanding......
99 cars had forged pistons with a softer cam profile than 96-98 cars. I think a mid way point in profile between 96-98 and 2000 and beyond. That's my understanding......
Keller
Enthusiast
So your saying that 99's had forged pistons but the softer cams? This would not make sense if what 2 bad4u is saying is true about new cam designs to promote the change in piston design. Could someone please elaborate on this?
Thanks
Josh
Thanks
Josh
Keller
Enthusiast
Cody
Thanks for the knowledgable reply. You are correct in your assumption that I'm looking to purchase a Viper. I'm looking for a low mileage 98-00. I'm going to add a supercharger and was wondering which engine would stand up in the LONG-TERM to forced induction. It sounds like the 00+ engines are tighter and thus allow less blowby but the forged pistons of the 99- may last longer. I would personally want to have a quiter engine and the chances of a piston letting go under 5-7 psi of boost seems minimal.
Thanks for the knowledgable reply. You are correct in your assumption that I'm looking to purchase a Viper. I'm looking for a low mileage 98-00. I'm going to add a supercharger and was wondering which engine would stand up in the LONG-TERM to forced induction. It sounds like the 00+ engines are tighter and thus allow less blowby but the forged pistons of the 99- may last longer. I would personally want to have a quiter engine and the chances of a piston letting go under 5-7 psi of boost seems minimal.
C O D Y
Enthusiast
I'm not a supercharger guy, so I can't help you there. I would however advise you to call Doug Levin in Fl. and talk to him. He is by far the most knowledgable about supercharging a viper.
Do a search on the board and you'll find his number.
And he's one of the nicest guys around.
Clint Sever, Yes you are correct on the year change of the pistons.
I think there has been running changes in the cams almost every year. NGR was one of the reasons for the changes.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Keller:
Cody
Thanks for the knowledgable reply. You are correct in your assumption that I'm looking to purchase a Viper. I'm looking for a low mileage 98-00. I'm going to add a supercharger and was wondering which engine would stand up in the LONG-TERM to forced induction. It sounds like the 00+ engines are tighter and thus allow less blowby but the forged pistons of the 99- may last longer. I would personally want to have a quiter engine and the chances of a piston letting go under 5-7 psi of boost seems minimal.
<HR></BLOCKQUOTE>
Do a search on the board and you'll find his number.
And he's one of the nicest guys around.
Clint Sever, Yes you are correct on the year change of the pistons.
I think there has been running changes in the cams almost every year. NGR was one of the reasons for the changes.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Keller:
Cody
Thanks for the knowledgable reply. You are correct in your assumption that I'm looking to purchase a Viper. I'm looking for a low mileage 98-00. I'm going to add a supercharger and was wondering which engine would stand up in the LONG-TERM to forced induction. It sounds like the 00+ engines are tighter and thus allow less blowby but the forged pistons of the 99- may last longer. I would personally want to have a quiter engine and the chances of a piston letting go under 5-7 psi of boost seems minimal.
<HR></BLOCKQUOTE>
2BADD 4U
Enthusiast
Guys...The response I left was given to me by David ***** ...I was asking the same question a few weeks ago. This reply is by him...see below...direct any questions to him.
Thanks, Dave
By Dave ***** :
I am lurking today and having fun online since the rain won't let me play with my supercharged baby...
In 1999, Chrysler deemed it necessary to change the pistons due to several reasons. Most were the escalating transmission complaints and the quick to replace a tranny dealers who were scamming the factory for new trannys.
Another reason was emissions, but not entirely. The actual emission output is exactly the same as it was in 1997. In some cases it is worse.
The newer pistons are different as well as the rods. The different parts will not interchange between years. With the lumpy cam you could run a much stronger forged piston and have lotsa torque. It also worked very well at higher piston speeds. The offset of this was greater thermal expansion and skirt slap. When you soften a camshaft and everyone wants power, you have to find it elsewhere. The intake was already close to max effiency and the heads could not be modified without having to recertify the engine. The only other change that could be made was to change the piston design.
What is different is that the hyperpathetic pistons are a high silicon content design. With this they are thermally stronger to a small window. This allows a closer piston to wall clearance which leads itself to less blowby, lower tension rings, and reduced emissions. In addition to this, Chrysler engineers wanted to be sure that they kept the power levels up so the wrist pin weight was changed. You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
The drawback is that once the peak thermal limit has been reached for a hyperpathetic piston, it flakes or cracks away. It literally self destructs. It will not hold its heat treating and will shatter like glass. Forged pistons will hold their structure, yet will actually melt at much higher temps due to the slow annealing process in their heat treating. This is why forged pistons are the ones of choice for all big nitrous and forced induction applications.
What can be done? You can ceramic coat the Creampuff slugs and forget the problems, or buy a $1000.00 worth of new forged pistons. Ceramic coating costs about $500.00 and is worth gold plating. Ford now supplies ALL its new 4.6 and 5.4 engines with ceramic coated pistons. They do this to reduce all scuffing and to eliminate all possible piston failures with their forced induction systems.
Just some good .02c worth.
Visit the ViperNation.com site and post there. Find the real tech answers on this site, not just speculation. Of course, one of you can cut and paste this to the VCA page so all can read it....
Have a Great Weekend!!
David A. *****
832-282-4004 http://www.davidawilks.com
Thanks, Dave
By Dave ***** :
I am lurking today and having fun online since the rain won't let me play with my supercharged baby...
In 1999, Chrysler deemed it necessary to change the pistons due to several reasons. Most were the escalating transmission complaints and the quick to replace a tranny dealers who were scamming the factory for new trannys.
Another reason was emissions, but not entirely. The actual emission output is exactly the same as it was in 1997. In some cases it is worse.
The newer pistons are different as well as the rods. The different parts will not interchange between years. With the lumpy cam you could run a much stronger forged piston and have lotsa torque. It also worked very well at higher piston speeds. The offset of this was greater thermal expansion and skirt slap. When you soften a camshaft and everyone wants power, you have to find it elsewhere. The intake was already close to max effiency and the heads could not be modified without having to recertify the engine. The only other change that could be made was to change the piston design.
What is different is that the hyperpathetic pistons are a high silicon content design. With this they are thermally stronger to a small window. This allows a closer piston to wall clearance which leads itself to less blowby, lower tension rings, and reduced emissions. In addition to this, Chrysler engineers wanted to be sure that they kept the power levels up so the wrist pin weight was changed. You see, when you take valve duration away from the cam you have to get it somewhere else. So, they raise the pin height in the piston to increase its dwell time at Top Dead & Bottom Dead Center. This adds greater cylinder filling and more squench with every revolution. Another reason why Creampuffs respond SO well to nitrous and supercharging.
The drawback is that once the peak thermal limit has been reached for a hyperpathetic piston, it flakes or cracks away. It literally self destructs. It will not hold its heat treating and will shatter like glass. Forged pistons will hold their structure, yet will actually melt at much higher temps due to the slow annealing process in their heat treating. This is why forged pistons are the ones of choice for all big nitrous and forced induction applications.
What can be done? You can ceramic coat the Creampuff slugs and forget the problems, or buy a $1000.00 worth of new forged pistons. Ceramic coating costs about $500.00 and is worth gold plating. Ford now supplies ALL its new 4.6 and 5.4 engines with ceramic coated pistons. They do this to reduce all scuffing and to eliminate all possible piston failures with their forced induction systems.
Just some good .02c worth.
Visit the ViperNation.com site and post there. Find the real tech answers on this site, not just speculation. Of course, one of you can cut and paste this to the VCA page so all can read it....
Have a Great Weekend!!
David A. *****
832-282-4004 http://www.davidawilks.com
C O D Y
Enthusiast
I have purchased both forged and cast piston vipers new.
I will tell you that I prefer the 00 and up over the 96 to 99 ones. The engines I've had feel much tighter and go through much less oil.
1,400 miles on the 2002 and it hasn't burnt 1 drop of oil. By far the tightest engine I've had on a viper.
Here's is some info on the cams of a 2002 and 1996
..........................2002.............1996
Bearing Journal Diamter..........SAME
Bore Diameter....................SAME
Diametrical Clearance............SAME
End Play.........................SAME
Valve Timing Exhaust Valve
Closes (ATC).............36.5.............42.5
Opens (BBC)..............88.5..............82.5
Duration.................305.0.....SAME ...305.0
Valve Timing Intake Valve
Closes (BTDC).............86.5....SAME ....86.5
Opens.....................23.5....SAME.... 23.5
Duration..................60.0 ............66.0
Say what you want about the cams, however I feel that it's more a placebo(SP) to people rather than anything else.
When choosing between older and newer vipers, I would let the color choices from the years and ABS options be more of an issue.
I've said it before and I'll say it again, there are stronger and weaker engines from every year. But if for one minute you think that you're going to like the sound of a 1996 over a 2000, you're high. They both sound like crap and need a catback to sound half good.
There are much more inportant issues to look at when buying a viper, like if the 998 and 999 recal on '96 to '99 was done correctly, what your budget can afford, and most importantly the condition and care the previous owner as taken of the vehicle.
I will tell you that I prefer the 00 and up over the 96 to 99 ones. The engines I've had feel much tighter and go through much less oil.
1,400 miles on the 2002 and it hasn't burnt 1 drop of oil. By far the tightest engine I've had on a viper.
Here's is some info on the cams of a 2002 and 1996
..........................2002.............1996
Bearing Journal Diamter..........SAME
Bore Diameter....................SAME
Diametrical Clearance............SAME
End Play.........................SAME
Valve Timing Exhaust Valve
Closes (ATC).............36.5.............42.5
Opens (BBC)..............88.5..............82.5
Duration.................305.0.....SAME ...305.0
Valve Timing Intake Valve
Closes (BTDC).............86.5....SAME ....86.5
Opens.....................23.5....SAME.... 23.5
Duration..................60.0 ............66.0
Say what you want about the cams, however I feel that it's more a placebo(SP) to people rather than anything else.
When choosing between older and newer vipers, I would let the color choices from the years and ABS options be more of an issue.
I've said it before and I'll say it again, there are stronger and weaker engines from every year. But if for one minute you think that you're going to like the sound of a 1996 over a 2000, you're high. They both sound like crap and need a catback to sound half good.
There are much more inportant issues to look at when buying a viper, like if the 998 and 999 recal on '96 to '99 was done correctly, what your budget can afford, and most importantly the condition and care the previous owner as taken of the vehicle.
