Adjusting Solid Lifters
It seems like each person has their own way of adjusting valve lash. As with hydraulic lifters, talked about in the previous post, there is nothing mysterious or complicated about adjusting the valve lash. The valve being adjusted must be fully closed. That is the only rule that matters. Whatever procedure you want to use is up to you. The content of this post will be about the lash itself and not the adjusting procedure.
Since the solid lifter does not have the ability to take-up the clearance created in the valve train, there will always be some running clearance in a hot engine. Most engines will gain clearance in the valve train from a cold to a hot engine. I’m sure there are exceptions, but I have not come across one. This gain in clearance is taken into consideration when designing the cam profile ramps for a particular engine combination. A cast iron push rod engine will not gain as much clearance as an all aluminum push rod engine. The ramps should be designed differently for each application. Many times a cam profile is used without any thought given to what the actual running lash was designed to be. The more lash, the less area the cam profile has. The opening and closing valve velocity points will also increase which could cause mechanical damage to the valve train. Less lash will increase the seat-to-seat duration, which may bleed-off cylinder pressure. Changing the rocker arm ratio also changes the lash setting. There is more to choosing the correct cam profile than just lift and duration numbers.
The valve lash settings come from the cam profile design. It is not just some number that is made up. The material of the engine block and heads, the rocker arm ratio that will be used, and the application, are all considered when designing the cam profile ramps. Older cam profiles were mostly designed for cast iron engines with 1.5 or 1.6 rocker ratios. Many engines today are all aluminum or have aluminum heads and higher rocker arm ratios. Again, the best performing cam profiles will be the ones that are designed specifically for your combination and application.
I will finish this post the same as the previous post. I know all kinds of combinations and lash adjustments are used for camshafts and lifters. I have already stated many times the disadvantages and dangers of mismatching cam profiles and lifters. I will just continue to shake my head and be amazed at why this is done.
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