[Chrysler300] saving time while adjusting valves

[Paul Holmgren <paulholm@xxxxxxxxxxxxx>]

Compensating for a Cold Engine when Adjusting Valve Lash

When installing a new cam, the engine will be cold but the lash 
specifications are for a hot engine.
What are you to do?
There is a correction factor that can be used to get close.
We mentioned that the alloy of the engine parts can be affected by 
thermal expansion in different ways, therefore the amount of correction 
factor to the lash setting depends on whether the cylinder heads and 
block are made out of cast iron or aluminum.

You can take the "hot" setting given to you in the catalog or cam 
specification card and alter it by the following amount to get a "cold" 
lash setting.

With iron block and iron heads, add .002"
With iron block and aluminum heads, subtract .006".
With both aluminum block and heads, subtract .012".
Remember this correction adjustment is approximate and is only meant to 
get you close for the initial start up of the engine. After the engine 
is warmed up to its proper operating temperature range, you must go back 
and reset all the valves to the proper "hot" valve lash settings.

Using Valve Lash to Help Tune the Engine

The engine only responds to the actual movement of the valves. Since the 
valve cannot move until all the running clearance (valve lash) has been 
taken up, the amount of valve lash you use affects the engine's 
performance. For example, if you decrease the amount of (hot) valve 
lash, the valve will open slightly sooner, lift higher, and close later. 
This makes the camshaft look bigger to the engine, because of a slight 
increase of actual running duration and lift. If you increase the amount 
of (hot) lash the opposite occurs. The valve will open later, lift less, 
and close sooner.

This shows the engine a smaller cam with slightly less actual running 
duration and lift. You can use this method on a trial basis to see what 
the engine responds to and keep the setting that works the best. Just 
remember, the more lash you run, the noisier the valve train will be. If 
the clearance is excessive it can be harsh on the other valve train 
components. Therefore, for prolonged running of the engine we do not 
recommend increasing the amount of hot lash by more than +.004" from the 
recommended setting. Nor do we recommend decreasing the hot lash by more 
than -.008".

Warning:

"Tight Lash" camshafts cannot deviate from the recommended hot lash 
setting by more than +.002" increase, or -.004" decrease. "Tight Lash" 
cams are those which have recommended valve settings of only .010", 
.012", or .014" on the specification card. These lobe designs have very 
short clearance ramps and cannot tolerate any increase in the 
recommended valve lash. The extra clearance can cause severe damage to 
valve train components.

With "Tight Lash" cams, we recommend using only the prescribed amount of 
hot valve lash, and that close inspection of the engine be maintained. 
Please realize that changing valve lash settings from the recommended 
design specifications will change the harmonic characteristics of the 
valve train, possibly causing valve spring deterioration and breakage.

ALSO

http://www.centuryperformance.com/valveadjustment.asp

-- 
Paul Holmgren
2 57 300-C's in Indy
Hoosier Corps L#6





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