Valve Lash and Cam Timing

Old 08-14-2010, 05:34 AM
  #1  
jreiley
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Default Valve Lash and Cam Timing

How does the valve lash effect the cam's valve timing? For example, i bought a engine with a Lunati solid lifter cam. The valve lash for both intake and exhause is.030. What does this do for the engine?
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Old 08-14-2010, 08:02 AM
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bowhay
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looser valve lash will give u more top end, tighter will give u more torque of the bottom
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Old 08-14-2010, 09:54 AM
  #3  
markdunlap
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Default valve timing

Are you sure about that? Loosening the valve lash makes the cam seem smaller, which helps bottom end performance. Tightening makes rthe cam seem larger, which helps the top end. That has been my experience.

If you play with lash up to .004 looser and tighter, you may find minor improvement. It will also tell you if cam you have is too large or small if it wants lash set different than factory setting. I set lash .006" tighter cold than hot specs for BBC with aluminum heads and iron block.
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Old 08-14-2010, 09:55 AM
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TopspeedLowet
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Default Wrong

Originally Posted by bowhay
looser valve lash will give u more top end, tighter will give u more torque of the bottom
This advice given above is exactly wrong. More lash gives less duration and tighter gives more duration. More duration will enhance the top end and likely remove some from the bottom end. You must respect the manufactures intended valve lash and not deviate more than .010" either way, too louse a setting will hammer the lifter off the lobe causing damage.
Bruce
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Old 08-14-2010, 04:50 PM
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Tod74
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Default Re: Wrong

Originally Posted by TopspeedLowet
Originally Posted by bowhay
looser valve lash will give u more top end, tighter will give u more torque of the bottom
This advice given above is exactly wrong. More lash gives less duration and tighter gives more duration. More duration will enhance the top end and likely remove some from the bottom end. You must respect the manufactures intended valve lash and not deviate more than .010" either way, too louse a setting will hammer the lifter off the lobe causing damage.
Bruce

X2....I know first hand about the roller damage. I used to think they would tighten up when HOT...of course this is 100% wrong but back then I didn't know...I set them cold just a little loose thinking they would be just right when hot....it's the opposite.I busted a roller lifter(and a block) after 20 something passes. live and learn.
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Old 08-14-2010, 11:43 PM
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suicidebomb
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Would anyone care to elaborate, on the "correct" way to adjust valve lash? :twisted:

I'll get the popcorn, and drinks.
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Old 08-14-2010, 11:54 PM
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Tod74
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Originally Posted by suicidebomb
Would anyone care to elaborate, on the "correct" way to adjust valve lash? :twisted:

I'll get the popcorn, and drinks.
:lol: I remember that...
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Old 08-15-2010, 04:38 AM
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fla1976
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This is how I adjust valves. The website has excellent info on valve adjustments but there is too much info to list here.

http://www.centuryperformance.com/ad...h-spg-149.html



Valve Adjustment Procedure - The Quick and Accurate Way:
First, view this little chart below for Small and Big Block Chevy Engines that I made and see if you can understand it. There is more of an explanation below the chart. For other engines you will use the firing order that matches your engine to create a similar chart. This chart is based upon "opposite" cylinders of your firing order. (see below)
Intake Valve Adjustment: ENGINE OFF!
■with #1 cylinder Intake Valve at full valve lift .... Adjust #6 Intake Valve
■with #8 cylinder Intake Valve at full valve lift .... Adjust #5 Intake Valve
■with #4 cylinder Intake Valve at full valve lift .... Adjust #7 Intake Valve
■with #3 cylinder Intake Valve at full valve lift .... Adjust #2 Intake Valve
■with #6 cylinder Intake Valve at full valve lift .... Adjust #1 Intake Valve
■with #5 cylinder Intake Valve at full valve lift .... Adjust #8 Intake Valve
■with #7 cylinder Intake Valve at full valve lift .... Adjust #4 Intake Valve
■with #2 cylinder Intake Valve at full valve lift .... Adjust #3 Intake Valve
Exhaust Valve Adjustment: ENGINE OFF!
You will notice that this is the same procedure and sequence as the intake valves listed above. Only now you are adjusting ONLY the exhaust valves the same way.
■with #1 cylinder Exhaust Valve at full valve lift .... Adjust #6 Exhaust Valve
■with #8 cylinder Exhaust Valve at full valve lift .... Adjust #5 Exhaust Valve
■with #4 cylinder Exhaust Valve at full valve lift .... Adjust #7 Exhaust Valve
■with #3 cylinder Exhaust Valve at full valve lift .... Adjust #2 Exhaust Valve
■with #6 cylinder Exhaust Valve at full valve lift .... Adjust #1 Exhaust Valve
■with #5 cylinder Exhaust Valve at full valve lift .... Adjust #8 Exhaust Valve
■with #7 cylinder Exhaust Valve at full valve lift .... Adjust #4 Exhaust Valve
■with #2 cylinder Exhaust Valve at full valve lift .... Adjust #3 Exhaust Valve
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Old 08-15-2010, 05:16 AM
  #9  
demented
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Originally Posted by fla1976
This is how I adjust valves. The website has excellent info on valve adjustments but there is too much info to list here.

http://www.centuryperformance.com/ad...h-spg-149.html



Valve Adjustment Procedure - The Quick and Accurate Way:
First, view this little chart below for Small and Big Block Chevy Engines that I made and see if you can understand it. There is more of an explanation below the chart. For other engines you will use the firing order that matches your engine to create a similar chart. This chart is based upon "opposite" cylinders of your firing order. (see below)
Intake Valve Adjustment: ENGINE OFF!
■with #1 cylinder Intake Valve at full valve lift .... Adjust #6 Intake Valve
■with #8 cylinder Intake Valve at full valve lift .... Adjust #5 Intake Valve
■with #4 cylinder Intake Valve at full valve lift .... Adjust #7 Intake Valve
■with #3 cylinder Intake Valve at full valve lift .... Adjust #2 Intake Valve
■with #6 cylinder Intake Valve at full valve lift .... Adjust #1 Intake Valve
■with #5 cylinder Intake Valve at full valve lift .... Adjust #8 Intake Valve
■with #7 cylinder Intake Valve at full valve lift .... Adjust #4 Intake Valve
■with #2 cylinder Intake Valve at full valve lift .... Adjust #3 Intake Valve
Exhaust Valve Adjustment: ENGINE OFF!
You will notice that this is the same procedure and sequence as the intake valves listed above. Only now you are adjusting ONLY the exhaust valves the same way.
■with #1 cylinder Exhaust Valve at full valve lift .... Adjust #6 Exhaust Valve
■with #8 cylinder Exhaust Valve at full valve lift .... Adjust #5 Exhaust Valve
■with #4 cylinder Exhaust Valve at full valve lift .... Adjust #7 Exhaust Valve
■with #3 cylinder Exhaust Valve at full valve lift .... Adjust #2 Exhaust Valve
■with #6 cylinder Exhaust Valve at full valve lift .... Adjust #1 Exhaust Valve
■with #5 cylinder Exhaust Valve at full valve lift .... Adjust #8 Exhaust Valve
■with #7 cylinder Exhaust Valve at full valve lift .... Adjust #4 Exhaust Valve
■with #2 cylinder Exhaust Valve at full valve lift .... Adjust #3 Exhaust Valve
Yes but this info needs to be adjusted for altered cams, 4-7 swap cams or 4-7-,2-3 swap cams.

The easiest way I have been taught to adjust valves is from reher morrison. If you take one cylinder at a time, when the exhaust valve begins to open you adjust the intake valve, Rotate the motor and when the intake valve begins to close adjust the exhaust valve.
I also found that when I set the lash cold i need to go back around once the motor warms up and adjust them again because it changes significantly. I always check them now when the motor is hot.
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Old 08-15-2010, 09:40 AM
  #10  
et7333
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when the intake valve begins to close



Its when the intake is ALMOST closed adjust the exhaust valve on that particular cylinder.
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