LT1-LT4 Modifications 1993-97 Gen II Small Block V8

questions about LT1 SR motor and power

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Old 08-25-2010, 02:40 PM
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Originally Posted by quik95lt1
I meant what procedure did you use to adjust the lash? For example, rotate the motor till both valves are closed then do the lash?...etc. When in the rotation of the motor did you adust the lash?

It should've been done like this.....

Rotate the motor till the exhaust valve begins to open....at this point adust the intake valve lash.

Then rotate the motor till the intake valve starts to return from full lift....at this point adjust the exhaust valve lash.

Doing it this way will ensure that you are on the bottom of the lobe of the cam. Adjusting them both while both valves are closed does not ensure that you are on the bottom of the lobe. (Just an FYI)

This method is right on and the only way to really ensure accuracy in setting lash. Also, was the lash recommendations from the cam manufacturer given in "hot" or "cold"? Most manufacturers give them in "hot"....but in my opinion it's better to recalculate those measurements and set them when the engine is cold. The engine cools quite a bit in the first 30 minutes of turning off (from full operating temp).
Old 08-25-2010, 02:45 PM
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Originally Posted by JasonShort
This method is right on and the only way to really ensure accuracy in setting lash. Also, was the lash recommendations from the cam manufacturer given in "hot" or "cold"? Most manufacturers give them in "hot"....but in my opinion it's better to recalculate those measurements and set them when the engine is cold. The engine cools quite a bit in the first 30 minutes of turning off (from full operating temp).
yea ur absolutly right......i do mine cold and add .006 for expansion to my numbers......i found running mine a bit tight makes me a bit quicker..........anyway i just wanted to make sure he did them right and wasnt hanging a valve open or anything......
Old 08-25-2010, 03:00 PM
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Originally Posted by quik95lt1
yea ur absolutly right......i do mine cold and add .006 for expansion to my numbers......i found running mine a bit tight makes me a bit quicker..........anyway i just wanted to make sure he did them right and wasnt hanging a valve open or anything......
That is EXACTLY what I do. I usually add .005" to the "hot" setting. But, I too have found that running the lash a little tighter than the lash settings from the cam manufacturer helped out quite a bit.
Old 08-25-2010, 05:13 PM
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if it gets faster with tighter lash, i'd retard the cam, and if you still pick up your engine wants more camshaft. measure the lash at full operating temp, then measure it with the engine cold so you know the difference between the two on YOUR MOTOR. Head deck thickness, rocker material, valve material, etc will all change how much the lash moves around with engine temp changes.
Old 08-26-2010, 07:37 AM
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Originally Posted by Wicked94Z
if it gets faster with tighter lash, i'd retard the cam, and if you still pick up your engine wants more camshaft. measure the lash at full operating temp, then measure it with the engine cold so you know the difference between the two on YOUR MOTOR. Head deck thickness, rocker material, valve material, etc will all change how much the lash moves around with engine temp changes.
my problem is i cant move the cam from where it is or im going to have piston to valve issues......its reeeealllyyyyy close as it is now.....
Old 08-26-2010, 07:52 AM
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Originally Posted by JasonShort
Alot of good advice here. You may want to check out the knock sensor settings in the PCM as well. I've had to completely turn off all KS input on my SR motors.
As do I. There's no way a knock sensor can function normally with a solid roller application.
Old 08-26-2010, 08:36 AM
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Originally Posted by SS RRR
As do I. There's no way a knock sensor can function normally with a solid roller application.
absolutly....completely shut them off they WILL NOT handle a SR valvetrain.....
Old 08-26-2010, 08:44 AM
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Definitely, knock sensor is pulling timing out because of SR valve train noise....that would explain the huge drop at 4500RPM.
Old 08-26-2010, 09:27 PM
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Originally Posted by quik95lt1
my problem is i cant move the cam from where it is or im going to have piston to valve issues......its reeeealllyyyyy close as it is now.....
ahhh. I'm sure Ai has some ideas for a new camshaft that will compliment that single plane setup, and stout new converter I traded a bigger dome (usually bad) for big valve reliefs, but I could probably run 280+ <106lsa and have plenty of room
Old 08-27-2010, 07:34 AM
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Originally Posted by Wicked94Z
ahhh. I'm sure Ai has some ideas for a new camshaft that will compliment that single plane setup, and stout new converter I traded a bigger dome (usually bad) for big valve reliefs, but I could probably run 280+ <106lsa and have plenty of room
yea id like to stuff a bit more duration into it if i could....maybe like 6-7 degrees on both sides that'd put me in the high 260s/ low 270's
Old 08-27-2010, 07:42 PM
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I'm guessing you're close on the exhaust, or is it intake as well? With that single plane and converter you can spread the lobe centers, and add intake duration. So you're effectively keeping overlap relatively the same, but more exhaust biased. With the single plane the pressure differential will hold on longer after TDC, so you don't NEED to jump start the intake charge so early especially if it's on a street driven application. You're not hurting for compression or head flow so it'll still make plenty of torque, but I'll scream for a BROAD range of rpm up top.



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