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Old 09-01-2008, 10:49 PM
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Valve lash question

What should I set the lash at on a small block chevy with hydraulic lifters but with Roller tip rockers?

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Old 09-01-2008, 10:52 PM
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Zero lash plus 1/2 to 3/4 turn on the rocker nut.
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Old 09-01-2008, 10:54 PM
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Quote:
Originally Posted by techinspector1
Zero lash plus 1/2 to 3/4 turn on the rocker nut.

I have it set at 8 thou right now should I go with zero lash???
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Old 09-01-2008, 11:08 PM
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Here's the bulletproof way to do it. Pull the valve covers and spark plugs. With your thumb on #1 plug hole (driver's side, front), turn the motor over clockwise with a socket on the damper retaining bolt on the crank until you begin to feel pressure on your thumb. Continue turning the crank while watching the timing tab and bring the crank up to TDC where the tab lines up with the groove cut into the damper. This will put you on TDC #1 firing position where the valves are closed and the lifters are on the heel of the cam lobe.

Starting at #1, jiggle the pushrods up and down with your forefinger and thumb and tighten down the rocker nut on each one until there is no play. Tighten the rocker nuts an additional 3/4 of a turn (270 degrees) or like from 12 O'Clock to 9 O'Clock on a clock face. Now, put the socket on the crank nut and turn the crank clockwise 1/4 turn (90 degrees), like from 12 O'Clock noon to 3 O'Clock on a clock face. This will put #8 cylinder on TDC firing position. Adjust both rockers on #8 cylinder (passenger side, rear). Now, turn the crank another 1/4 turn and adjust #4 rockers (passenger side, second from the front). Turn the crank another 1/4 turn and adjust #3 rockers (driver's side, second from front). Turn the crank another 1/4 turn and adjust #6 rockers (passenger side, third from the front). Turn the crank another 1/4 turn and adjust #5 rockers (driver's side, third from the front). Turn the crank another 1/4 turn and adjust #7 rockers (driver's side, rear). Turn the crank another 1/4 turn and adjust #2 rockers (passenger side, front).

Use only the "jiggle up and down method" of determining play in the pushrods. Twisting them will give you the wrong lash because THEY WILL END UP TOO TIGHT.

To summarize, bring each cylinder up to TDC firing, jiggle each of the pushrods for that cylinder up and down until all play is removed, tighten each rocker down an additional 3/4 of a turn after all play is removed.

The reason for removing all spark plugs before beginning is.....
1. To make the motor easier to turn over.
2. To prevent the piston from "rocking back" against compression and giving you an erroneous reading.

The only time you would set the valves with a measureable lash would be with a solid lifter camshaft. And even at that, you wouldn't use a lash that tight, more like 0.025".

Last edited by techinspector1; 09-01-2008 at 11:17 PM.
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