1.8 Ratio Gm Ls7 Rocker Swap
05-18-2006, 11:13 AM
#41
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Originally Posted by Dan_the_C5_Man
Well crap, got all excited and then reality came crashing down; Thank You Phil for taking the time to come forward "just because".
I have nearly 1000 miles on my motor.. RoadRebel has about 8000 on his...
05-18-2006, 10:05 PM
#42
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1:8's with xer cam
Big daddy. I have the same cam as you I think. Comp cam XER273-14?? If so I spoke to Comp today about the 1:8's and they definately did not advise the 1:8 rockers the LS7's or any other than the stock 1:7's as the lobe is to aggressive and it would make it unstable.??
May want to check with your cam supplier if it is not the same cam though. Mt .02
May want to check with your cam supplier if it is not the same cam though. Mt .02
05-18-2006, 10:18 PM
#43
Le Mans Master
Originally Posted by BLOWNZO6
Which reality came crashing down?
I have nearly 1000 miles on my motor.. RoadRebel has about 8000 on his...
I have nearly 1000 miles on my motor.. RoadRebel has about 8000 on his...
The difference in our "realities" is I have some certainty that I won't drop a valve or hole a piston, something I simply cannot afford, whereas you are willing to take those risks. Good for you, I am envious, but it is good to have folks like Phil come forward so we may all make an informed decision. Otherwise all we have to go on is "mine hasn't blown up yet".
Last edited by Dan_the_C5_Man; 05-18-2006 at 10:23 PM.
05-18-2006, 10:35 PM
#44
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Originally Posted by Scooter1964
Big daddy. I have the same cam as you I think. Comp cam XER273-14?? If so I spoke to Comp today about the 1:8's and they definately did not advise the 1:8 rockers the LS7's or any other than the stock 1:7's as the lobe is to aggressive and it would make it unstable.??
May want to check with your cam supplier if it is not the same cam though. Mt .02
May want to check with your cam supplier if it is not the same cam though. Mt .02
Well that bites the big one! I was looking forward to doing something new! I will give them a call tomorrow... maybe the guy you spoke to didn't know what he was talking about! LOL
05-19-2006, 07:11 AM
#45
Premium Supporting Vendor
Originally Posted by Dan_the_C5_Man
No offense, but your priorities and tolerances are different than mine (and possibly others); that's obvious, you’re running FI for goodness sake, and I barely pulled the trigger on an LPE GT2-3 cam, most folks wouldn't even bother w/ such a small bumb stick.
The difference in our "realities" is I have some certainty that I won't drop a valve or hole a piston, something I simply cannot afford, whereas you are willing to take those risks. Good for you, I am envious, but it is good to have folks like Phil come forward so we may all make an informed decision. Otherwise all we have to go on is "mine hasn't blown up yet".
The difference in our "realities" is I have some certainty that I won't drop a valve or hole a piston, something I simply cannot afford, whereas you are willing to take those risks. Good for you, I am envious, but it is good to have folks like Phil come forward so we may all make an informed decision. Otherwise all we have to go on is "mine hasn't blown up yet".
05-19-2006, 08:33 AM
#46
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Originally Posted by DynoTech Engineering
We were wondering when someone would ask this...
A few months ago, we had already mocked up a set of these rockers on an LS1 head, an LS6 head and an AFR head...and *NONE* of them have the correct valvetrain geometry for proper use~ especially for high RPM use. They will physically fit on the heads and the engine will run, but the rocker tip is located *extremely* far out onto the valve tip to the point where only the 1/3 outer edge of the valve tip is engaged on the rocker scrub pad, as measured with the cam on its base circle and the negative condition only gets worse throughout the rocker arm's arc....
Do *NOT* use these rocker arms on the LS1/LS6/LS2 application or we can gaurantee you with 100% certainty in every instance or application that you *WILL* have premature valvetrain failure sooner than later.
We just wanted to to try to stop someone from unknowingly damaging their engine from reading inaccurate information. Good luck to those who are running them or those that still want to try them anyway despite the warning...
Regards,
DTE
A few months ago, we had already mocked up a set of these rockers on an LS1 head, an LS6 head and an AFR head...and *NONE* of them have the correct valvetrain geometry for proper use~ especially for high RPM use. They will physically fit on the heads and the engine will run, but the rocker tip is located *extremely* far out onto the valve tip to the point where only the 1/3 outer edge of the valve tip is engaged on the rocker scrub pad, as measured with the cam on its base circle and the negative condition only gets worse throughout the rocker arm's arc....
Do *NOT* use these rocker arms on the LS1/LS6/LS2 application or we can gaurantee you with 100% certainty in every instance or application that you *WILL* have premature valvetrain failure sooner than later.
We just wanted to to try to stop someone from unknowingly damaging their engine from reading inaccurate information. Good luck to those who are running them or those that still want to try them anyway despite the warning...
Regards,
DTE
A shorter pushrod would not correct this?
05-19-2006, 09:16 AM
#47
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It's not that easy, for if it were, we would have done that already.
Additionally, it's not just a simple function of altering pushrod lengths to achieve proper rocker arm geometry from the rocker's fulcrum, because there are more factors involved to properly setting up valvetrain then pushrods alone... These LS7 rockers are not adjustable, therefore they are dependant on mounting stand height and set-back primarily.
The LS7 cylinder head does not have removable rocker arm tie-bar pedastals compared to the LS1/LS2/LS6/LQ9, etc, etc, etc. Conversly, the rocker arm stands are cast as one on the cylinder head and have a unique rocker arm stand placement for the long fulcrum point of the 1.8 ratio rocker arm to index to.
If you try to use these LS7 exhaust rockers on standard LSx tie-bar pedastal type engines, the fulcrum point of the LS7 rocker is approx. .113" longer than the the LSx-type rockers, which puts the LS7 rocker arm scrub pad on the extreme outer edge of the valve tip. Eventually that will form a negative wear pattern on the valve tip and the rocker arm and the premature valvetrain wear we spoke about above will shortly follow.
BTW- Crane Cams or Comp Cams rocker arms have taken this into account and are not manufactured that way...that's why they fit properly.
As we said before, they will *FIT* onto the engine and the engine *WILL* run, but that doesn't mean the application is correct or right, no matter how many miles are logged on them or how many engines they are put onto..
As also stated, the correct way to make these work is to machine custom rocker arm stands that take the new LS7 rocker arm stand height and back-set into account- (if there is enough valvetrain valley head room) but by the time you factor in that cost of machining those parts, one could have probably purchased new units from Crane or Comp Cams for nearly the same amount.
We've looked into machining special rocker arm stands for these rockers, but our plate is very full as it is and we just don't have the time to do it...yet.
Regards,
DTE
Additionally, it's not just a simple function of altering pushrod lengths to achieve proper rocker arm geometry from the rocker's fulcrum, because there are more factors involved to properly setting up valvetrain then pushrods alone... These LS7 rockers are not adjustable, therefore they are dependant on mounting stand height and set-back primarily.
The LS7 cylinder head does not have removable rocker arm tie-bar pedastals compared to the LS1/LS2/LS6/LQ9, etc, etc, etc. Conversly, the rocker arm stands are cast as one on the cylinder head and have a unique rocker arm stand placement for the long fulcrum point of the 1.8 ratio rocker arm to index to.
If you try to use these LS7 exhaust rockers on standard LSx tie-bar pedastal type engines, the fulcrum point of the LS7 rocker is approx. .113" longer than the the LSx-type rockers, which puts the LS7 rocker arm scrub pad on the extreme outer edge of the valve tip. Eventually that will form a negative wear pattern on the valve tip and the rocker arm and the premature valvetrain wear we spoke about above will shortly follow.
BTW- Crane Cams or Comp Cams rocker arms have taken this into account and are not manufactured that way...that's why they fit properly.
As we said before, they will *FIT* onto the engine and the engine *WILL* run, but that doesn't mean the application is correct or right, no matter how many miles are logged on them or how many engines they are put onto..
As also stated, the correct way to make these work is to machine custom rocker arm stands that take the new LS7 rocker arm stand height and back-set into account- (if there is enough valvetrain valley head room) but by the time you factor in that cost of machining those parts, one could have probably purchased new units from Crane or Comp Cams for nearly the same amount.
We've looked into machining special rocker arm stands for these rockers, but our plate is very full as it is and we just don't have the time to do it...yet.
Regards,
DTE
05-19-2006, 09:47 AM
#48
Le Mans Master
With the contact area on the outer edge of the valve stem, I can see where increased valve guide wear would be the next problem.
05-19-2006, 01:03 PM
#49
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Originally Posted by DynoTech Engineering
It's not that easy, for if it were, we would have done that already.
Additionally, it's not just a simple function of altering pushrod lengths to achieve proper rocker arm geometry from the rocker's fulcrum, because there are more factors involved to properly setting up valvetrain then pushrods alone... These LS7 rockers are not adjustable, therefore they are dependant on mounting stand height and set-back primarily.
The LS7 cylinder head does not have removable rocker arm tie-bar pedastals compared to the LS1/LS2/LS6/LQ9, etc, etc, etc. Conversly, the rocker arm stands are cast as one on the cylinder head and have a unique rocker arm stand placement for the long fulcrum point of the 1.8 ratio rocker arm to index to.
If you try to use these LS7 exhaust rockers on standard LSx tie-bar pedastal type engines, the fulcrum point of the LS7 rocker is approx. .113" longer than the the LSx-type rockers, which puts the LS7 rocker arm scrub pad on the extreme outer edge of the valve tip. Eventually that will form a negative wear pattern on the valve tip and the rocker arm and the premature valvetrain wear we spoke about above will shortly follow.
BTW- Crane Cams or Comp Cams rocker arms have taken this into account and are not manufactured that way...that's why they fit properly.
As we said before, they will *FIT* onto the engine and the engine *WILL* run, but that doesn't mean the application is correct or right, no matter how many miles are logged on them or how many engines they are put onto..
As also stated, the correct way to make these work is to machine custom rocker arm stands that take the new LS7 rocker arm stand height and back-set into account- (if there is enough valvetrain valley head room) but by the time you factor in that cost of machining those parts, one could have probably purchased new units from Crane or Comp Cams for nearly the same amount.
We've looked into machining special rocker arm stands for these rockers, but our plate is very full as it is and we just don't have the time to do it...yet.
Regards,
DTE
Additionally, it's not just a simple function of altering pushrod lengths to achieve proper rocker arm geometry from the rocker's fulcrum, because there are more factors involved to properly setting up valvetrain then pushrods alone... These LS7 rockers are not adjustable, therefore they are dependant on mounting stand height and set-back primarily.
The LS7 cylinder head does not have removable rocker arm tie-bar pedastals compared to the LS1/LS2/LS6/LQ9, etc, etc, etc. Conversly, the rocker arm stands are cast as one on the cylinder head and have a unique rocker arm stand placement for the long fulcrum point of the 1.8 ratio rocker arm to index to.
If you try to use these LS7 exhaust rockers on standard LSx tie-bar pedastal type engines, the fulcrum point of the LS7 rocker is approx. .113" longer than the the LSx-type rockers, which puts the LS7 rocker arm scrub pad on the extreme outer edge of the valve tip. Eventually that will form a negative wear pattern on the valve tip and the rocker arm and the premature valvetrain wear we spoke about above will shortly follow.
BTW- Crane Cams or Comp Cams rocker arms have taken this into account and are not manufactured that way...that's why they fit properly.
As we said before, they will *FIT* onto the engine and the engine *WILL* run, but that doesn't mean the application is correct or right, no matter how many miles are logged on them or how many engines they are put onto..
As also stated, the correct way to make these work is to machine custom rocker arm stands that take the new LS7 rocker arm stand height and back-set into account- (if there is enough valvetrain valley head room) but by the time you factor in that cost of machining those parts, one could have probably purchased new units from Crane or Comp Cams for nearly the same amount.
We've looked into machining special rocker arm stands for these rockers, but our plate is very full as it is and we just don't have the time to do it...yet.
Regards,
DTE
I forgot that they are not adjustable rockers. Makes sense now, thanks!
08-17-2018, 09:32 PM
#50
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back from the dead
Brownz!! how did those ls7 rockers go? I know this is years later but I'm reading mixed feedback and want to confirm with someone who has real experience.
did the rockers run fine? to confirm they're ls7 offsets on otherwise stock heads right?
really appreciate any feedback!
Dana
did the rockers run fine? to confirm they're ls7 offsets on otherwise stock heads right?
really appreciate any feedback!
Dana
