How bad is this? (pic)
Unfortunatley I already did a cam a couple years back...218/224 .527/.534 114 ...so I was hopeing for a little more lift with these rockers, instead of pulling the cam out again & putting in something a little bigger...oh well, I guess someone had to be the guinea pig
Registered User
Joined: Mar 2004
Posts: 199
Likes: 0
From: Austin, Texas
Originally Posted by Ditmeion
This is with the valve at full lift...notice the location of the rocker tip on the valve...looks like it is resting on the valve edge. These are the 1.8 LS7 exhaust rockers....with these rockers, it puts my lift to around .560
Am I asking for trouble wearing out the edges on my valves?
TIA
Am I asking for trouble wearing out the edges on my valves?
TIA
You will wear your guides out and probably your valves stems very quickly. You have somewhere around 300 lbs of spring pressure when the valve is fully open. This pressure is driving the valve stem into the side of the guide, which will break through any oil film you may have had, this will cause metal-to-metal wear. The LS1’s run a 5/16 valve stem, you have 300 lbs of side load on a piece of metal that’s only 5/16 around, the contact area between the guide and the valve stem will be very small. This will cause major wear, if you have the stock GM cast iron guides your guides will be shot in no time. If you think about the rpm the motor turns, and how many times in a minute the valves open and close it becomes very clear just how important the location of the tip of the rocker on the valve tip is. Also as this motor runs and begins to bell mouth the top and bottom of the guide the valves will begin to hit their seats off center.
This will cause the valves to bounce, which will cause a loss of dynamic compression, you will lose power, get worse gas mileage and wear out the valve train much quicker.
I would not recommend running this set-up for any length of time.
TECH Enthusiast
Joined: Jul 2002
Posts: 653
Likes: 0
From: Mannheim, Germany
Originally Posted by PortPros1
The real problem you have here is the side-load you are putting on the guides and valve stems.
You will wear your guides out and probably your valves stems very quickly. You have somewhere around 300 lbs of spring pressure when the valve is fully open. This pressure is driving the valve stem into the side of the guide, which will break through any oil film you may have had, this will cause metal-to-metal wear. The LS1’s run a 5/16 valve stem, you have 300 lbs of side load on a piece of metal that’s only 5/16 around, the contact area between the guide and the valve stem will be very small. This will cause major wear, if you have the stock GM cast iron guides your guides will be shot in no time. If you think about the rpm the motor turns, and how many times in a minute the valves open and close it becomes very clear just how important the location of the tip of the rocker on the valve tip is. Also as this motor runs and begins to bell mouth the top and bottom of the guide the valves will begin to hit their seats off center.
This will cause the valves to bounce, which will cause a loss of dynamic compression, you will lose power, get worse gas mileage and wear out the valve train much quicker.
I would not recommend running this set-up for any length of time.
You will wear your guides out and probably your valves stems very quickly. You have somewhere around 300 lbs of spring pressure when the valve is fully open. This pressure is driving the valve stem into the side of the guide, which will break through any oil film you may have had, this will cause metal-to-metal wear. The LS1’s run a 5/16 valve stem, you have 300 lbs of side load on a piece of metal that’s only 5/16 around, the contact area between the guide and the valve stem will be very small. This will cause major wear, if you have the stock GM cast iron guides your guides will be shot in no time. If you think about the rpm the motor turns, and how many times in a minute the valves open and close it becomes very clear just how important the location of the tip of the rocker on the valve tip is. Also as this motor runs and begins to bell mouth the top and bottom of the guide the valves will begin to hit their seats off center.
This will cause the valves to bounce, which will cause a loss of dynamic compression, you will lose power, get worse gas mileage and wear out the valve train much quicker.
I would not recommend running this set-up for any length of time.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Readjust your rocker geometry.
Do a wipe test and center your line on the valve tips.
Once geometry is centered, then measure desired p-rod length.
Either you'll shave from the pedestal or shim it, the wipe will determine that.
Do a wipe test and center your line on the valve tips.
Once geometry is centered, then measure desired p-rod length.
Either you'll shave from the pedestal or shim it, the wipe will determine that.
Originally Posted by Felix C
This is one case. Have other LS7 exhaust rocker installs on a GEN III engine resulted in the same situation?
TECH Resident
Joined: Dec 2004
Posts: 881
Likes: 1
The rocker is too low and possibly (probably) the wrong dimensions (valve-to-trunnion is too long). At full lift the center of the contact point (since there is no roller) to the center of the trunnion is pointing up at the valve. It should be perpendicular to the valve at mid-lift. Depending on the access of the rocker stud mounts, shimming the base of the rocker may fix the geometry.
Then you want to select the pushrod length that sets the center of the trunnion to center of the roller (here contact point) perpendicular to the valve at mid-lift with the desired preload. If the geometry is correct this should approximately move over the center of the valve stem during the rocker travel.
If the rocker studs are parallel to the valve stem, raising the rockers from shimming will actually make the situation worse (the tip will be off th valve entirely).
Then you want to select the pushrod length that sets the center of the trunnion to center of the roller (here contact point) perpendicular to the valve at mid-lift with the desired preload. If the geometry is correct this should approximately move over the center of the valve stem during the rocker travel.
If the rocker studs are parallel to the valve stem, raising the rockers from shimming will actually make the situation worse (the tip will be off th valve entirely).
Originally Posted by Ditmeion
I've heard others that have ran them just fine...some, I think, just install them becuase they were told they would work without really checking things like this out
I wouldn't run this at all. The only way you are going to get those rocker arms into allignment is to shave down the mounting bosses for the rocker pedistal. Did you look into this because this could be a problem. Do you have the LS1 or the LS7 rocker pedistal? The LS7 unit might be shorter and or taller and correct this issue. Just a thought. At this point it would be worth looking into.
