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Don
Don, Classic Car Mechanic
Category: Classic Car
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Experience:  30 years of experience and we have 4 classic cars our selfs
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Hemi..specs..I want to adjust the valve lash (solid lifters

Resolved Question:

Hi;

I have a 1968 426 hemi engine with basically stock specs. I want to adjust the valve lash (solid lifters). I have been told by a reputable hemi engine builder that he usually sets them tighter than specified (.016 intake, .020 exhaust instead of .028 & .032)in order to increase the performance. This will provide a bit more lift at the expense of idle quality. He indicates that this will not harm the engine, but i would like a second opinion.
Submitted: 4 years ago.
Category: Classic Car
Expert:  Don replied 4 years ago.
hi there my name is don i will try to help you in this

these specs are put into place by the engine manufa tures to obtain the best performance and economy and wear for that engine when you exceed these specs you are doing something that is not recommended by the manufacture
re member the phrase "every action has an equal and opposite reaction"

so would you set your valves so tight that you hit the top of the piston i think not

or would you set them to loose so that they clatter and damage the stems and does not work properly no again would you not tighten the head bolts to torque settings so that you have a differnt deck clearence height and you do not squeeze the head gasket ?
if you do this then you are effecting an engine in other areas by putting undo stress on other parts of the engine

ther are sveral ways to increase performance with out exceeding manufacture specs

example carb,air filter, oil ,exhaust and so on

but i think you get the point
in answer to your question stick with what the engine specs and settings are and make improvements in other areas
i hope this helps you
have agreat day
don
Don, Classic Car Mechanic
Category: Classic Car
Satisfied Customers: 1652
Experience: 30 years of experience and we have 4 classic cars our selfs
Don and other Classic Car Specialists are ready to help you
Expert:  Don replied 4 years ago.
hi thee and thanks for the accept it was my pleasure to assits you have agreat day
don
Expert:  Don replied 4 years ago.
hi there
in response to your feedback '

you question did not indecate a race engine just if it was a safe thing to do

even if it was a race engine which i hae built over 100 over the years i havenecer set the valve lash tigher than manufacture specs as it could cause valve float and possibly hit the top of the piston a rough idle means that the valves are not fully closing and allowing compression to escape around the valve and enter the top end
thanks fo the except again and you have a great day
don

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