Adjusting Valve Lash
There are numerous ways to lash valves in an engine. We will discuss only what
we feel are the best ways. The method that we prefer will work on any
camshaft
type, the only difference is the amount of lash that will be used. We use the
"firing order method" of lashing valves. We can lash the valves on an engine
stand and never have to readjust them once run in the car.
There are numerous
ways to lash valves in an engine. We will discuss only what we feel are the
best ways. The method that we prefer will work on any camshaft type, the only
difference is the amount of lash that will be used. We use the "firing order
method" of lashing valves. We can lash the valves on an engine stand and never
have to readjust them once run in the car.
Step #1 Find top dead center for piston #1
A lot of people think that if
the timing pointer is on the balancer mark that this is TDC #1. This is not
necessarily true, it can be TDC #6. This is because there are 720 degrees
crankshaft rotation in one complete firing sequence. There are two ways to find
TDC #1. First is by pulling the #1 spark plug, holding your finger over the hole
and turning the crankshaft until it tries to blow your finger away, then once
the timing mark comes up this will be TDC #1. The other method requires the
valve cover or intake to be off. You can look at the lifters or rockers of #1
and #6 cylinders. When #1 is at TDC, #6 has both valves open slightly. If you
move the balancer timing mark to each side of the timing pointer, you should see
both lifters or rockers of #6 moving up and down and #1 should remain
stationary. If it is vice versa then you are on TDC #6 and need to move the
crankshaft 360 degrees or one full turn.
Step #2 Adjust the the lash of #1 cylinder
This is where you have to
determine the lash you will use. If it is a solid or solid roller application
then the lash will generally be between .016" and .030". For hydraulic and
hydraulic roller applications we prefer to go 1/4 turn more than "0". We turn
the poly lock while moving the rocker arm up and down on the valve. Once all
play is taken out go 1/4 turn more and then lock down the inner set screw.
Another thing you can do at this point is go just shy of 1/4 turn, lock down the
inner set screw and then put the wrench on the poly lock and turn it as far as
you can, within reason. This helps lock down the poly lock to keep it from
backing off.
Step #3 Turn the crankshaft 90 degrees
Turn the crankshaft 90 degrees
or 1/4 turn to the next cylinder in the firing order. Repeat Step #2. The next
one in the firing order is obviously dependent on the engine you have. All V8
Chevys (small block and big block) are 1-8-4-3-6-5-7-2. 302HO and 351W are
1-3-7-2-6-5-4-8. Non-HO 302 and 289 are 1-5-4-2-6-3-7-8.
Step #4 Keep going
Keep turning the crank in 90
degree increments and lashing the valves for that cylinder until all 8 cylinders
have been adjusted. At that point you should have to turn the crank one more 90
degree turn and you will be back on #1 TDC.
For you serious race car
guys with gross duration figures in the 320 plus region you can use the firing
order sequence but instead of adjusting the #1 valves at TDC #1 adjust the
previous intake rocker and the next exhaust rocker. This ensures that the lifter
is on the absolute base circle of the camshaft.
V8 Chevys
| |
1 |
8 |
4 |
3 |
6 |
5 |
7 |
2 |
| in |
2 |
1 |
8 |
4 |
3 |
6 |
5 |
7 |
| ex |
8 |
4 |
3 |
6 |
5 |
7 |
2 |
1 |
302HO and 351W
| |
1 |
3 |
7 |
2 |
6 |
5 |
4 |
8 |
| in |
8 |
1 |
3 |
7 |
2 |
6 |
5 |
4 |
| ex |
3 |
7 |
2 |
6 |
5 |
4 |
8 |
1 |
Non-HO 302 and 289
|
|
1
|
5
|
4
|
2
|
6
|
3
|
7
|
8
|
|
in
|
8
|
1
|
5
|
4
|
2
|
6
|
3
|
7
|
|
ex
|
5
|
4
|
2
|
6
|
3
|
7
|
8
|
1
|
