Chuck 98 RT/10
Enthusiast
I've been asking about cam specs for years. Can't find it in the shop manual. Haven't seen them on this board.
Cam Changes with Year
- Thread starter Chuck 98 RT/10
- Start date
JBenko
Enthusiast
It would be great to hear from folks regarding other years spec's. My '96 RT/10 Service Manual shows:
Exhaust duration = 288.5 deg
Exhaust lift = .495 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 292.5 deg
Intake lift = .525 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 64.5 deg
Exhaust duration = 288.5 deg
Exhaust lift = .495 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 292.5 deg
Intake lift = .525 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 64.5 deg
treynor
Enthusiast
2001 RT/10:
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 60.0 deg
----
I found all the cam information in the "Specifications - Engine" section of my 2001 Service Manual.
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 60.0 deg
----
I found all the cam information in the "Specifications - Engine" section of my 2001 Service Manual.
Kevin ACR
Enthusiast
2000 Service Manual
same as the 2001 in the post Ben made:
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 60.0 deg
<HR></BLOCKQUOTE>
same as the 2001 in the post Ben made:
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 60.0 deg
<HR></BLOCKQUOTE>
RoyV101621
Enthusiast
Measurements can be the same and still have a change in profile.
1994
Exhaust Closes 43 deg
Exhaust opens 65.5 deg
Exhaust duration = 288.5 deg
Exhaust lift = .495 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake closes 91 deg
Intake opens 21.5 deg
Intake duration = 292.5 deg
Intake lift = .525 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 64.5 deg
GEN 1 major difference
1994
Exhaust Closes 43 deg
Exhaust opens 65.5 deg
Exhaust duration = 288.5 deg
Exhaust lift = .495 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake closes 91 deg
Intake opens 21.5 deg
Intake duration = 292.5 deg
Intake lift = .525 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 64.5 deg
GEN 1 major difference
MES
Enthusiast
I will add one more for 1997 GTS
Exhaust Closes 42.5 deg
Exhaust opens 82.5 deg
Exhaust duration = 305.0 deg
Exhaust lift = .541 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake closes 86.5 deg
Intake opens 23.5 deg
Intake duration = 297.0 deg
Intake lift = .541 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 66.0 deg
From what I see the 97 and up has more lift and duration than the 96 and older. Which would make sense because they have an extra 50 HP and higher peek HP. The only difference in the new cam from the 97 was a decrease in the valve overlap from 66 to 60, interesting.
Exhaust Closes 42.5 deg
Exhaust opens 82.5 deg
Exhaust duration = 305.0 deg
Exhaust lift = .541 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake closes 86.5 deg
Intake opens 23.5 deg
Intake duration = 297.0 deg
Intake lift = .541 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 66.0 deg
From what I see the 97 and up has more lift and duration than the 96 and older. Which would make sense because they have an extra 50 HP and higher peek HP. The only difference in the new cam from the 97 was a decrease in the valve overlap from 66 to 60, interesting.
Performin Norman
Enthusiast
1998 service manual reads
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 66.0 deg
Exhaust duration = 305.0 deg
Exhaust lift = .542 inch
Exhaust valve head diameter = 1.575 - 1.585 inch
Intake duration = 297.0 deg
Intake lift = .542 inch
Intake valve head diameter = 1.915 - 1.925 inch
Valve overlap = 66.0 deg
Chuck 98 RT/10
Enthusiast
So it looks like the rough idle (which is great!) isn't so much from lift but more a result of the valve overlap???
treynor
Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>So it looks like the rough idle (which is great!) isn't so much from lift but more a result of the valve overlap???<HR></BLOCKQUOTE>
Correct. I'm no mechanic, but let me take a stab at it (and then get flamed by those who really know what they're talking about
.
Cam overlap is a measure of how long both the intake and exhaust valves are simultaneously open. Overlap helps power at higher RPM because the exhaust gasses rushing out of the cylinders and through the headers have momentum, and keep moving after the piston has stopped pushing them. They thus create a vacuum which pulls the intake charge into the cylinder. Reflected exhaust pulses from the header's collector amplify this effect.
On the flip side, overlap can lead to an uneven idle and loss of low-RPM power because when the exhaust gasses are not flowing out of the cylinder at velocity, back pressure from the cats / mufflers / etc. will tend to reverse the flow of the exhaust and leave excess exhaust in the cylinder. This will in turn disrupt the flow of intake charge into the cylinder, leading to uneven amounts of intake charge and mixture levels, and thus lumpy idle.
Correct. I'm no mechanic, but let me take a stab at it (and then get flamed by those who really know what they're talking about
Cam overlap is a measure of how long both the intake and exhaust valves are simultaneously open. Overlap helps power at higher RPM because the exhaust gasses rushing out of the cylinders and through the headers have momentum, and keep moving after the piston has stopped pushing them. They thus create a vacuum which pulls the intake charge into the cylinder. Reflected exhaust pulses from the header's collector amplify this effect.
On the flip side, overlap can lead to an uneven idle and loss of low-RPM power because when the exhaust gasses are not flowing out of the cylinder at velocity, back pressure from the cats / mufflers / etc. will tend to reverse the flow of the exhaust and leave excess exhaust in the cylinder. This will in turn disrupt the flow of intake charge into the cylinder, leading to uneven amounts of intake charge and mixture levels, and thus lumpy idle.
HSSSTOY
Enthusiast
The 99 Viper is similar to 2000 model year as posted in this thread, with the excption of Valve Overlap = 66.0 deg.
99 Manual 9-49
99 Manual 9-49
BWoodbury
Enthusiast
Sounds right to me Ben. I recently asked about the awsome "race car" sound from one of our local Vipers. It really sounded like I was at the track. My buddy imediatly said that what I was hearing was the overlap.
So lets review, rough idle, more power but only at high RPMS. Sounds like a race engine to me.
So lets review, rough idle, more power but only at high RPMS. Sounds like a race engine to me.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MES:
..........From what I see the 97 and up has more lift and duration than the 96 and older. <HR></BLOCKQUOTE>
CORRECTION: 1996 GTS (1996.5) has the exact same (great) cam as 1997.......... The initial 1996 post was a Gen-I RT/10.
..........From what I see the 97 and up has more lift and duration than the 96 and older. <HR></BLOCKQUOTE>
CORRECTION: 1996 GTS (1996.5) has the exact same (great) cam as 1997.......... The initial 1996 post was a Gen-I RT/10.
For everyone who posted, I believe the numbers you are quoting are ADVERTISED numbers which normally don't mean much. What you really want to look at is @.50, the industry standard. I tried to see if there was a formula/correlation for converting advertised numbers but is seems to have a huge variation and range. Personally I have seen anywhere for 65% to 90%.
Thought this might help.
Thought this might help.
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