Jim, Listers
I hope you are making progress on fixing the backfire gremlin. I thought I
would take the opportunity to contribute my two cents worth to the List on
adjusting valves. Since I have a solid lifter flat tappet cam, I do this
procedure every few thousand miles. For the majority of you Listers with
hydraulic lifters, the procedure is basically the same, just tighten 1/4
turn past zero lash. First off, I don't adjust with the engine running.
Second, I don't adjust with the engine hot. Adjusting hot or cold is the
same if you have cast iron heads; if you have aluminum heads, that's another
story because the thermal expansion of iron/steel is different than cast
aluminum. In the case of aluminum heads, check the lash on one or two valves
right after you turn off the engine, then wait for it to cool off to a
comfortable temperature and check it again and correct the adjustments
accordingly. With the engine at a comfortable temperature you have plenty of
time and can do a very accurate job on the adjustments. When it's hot and
especially when it's running, it's a difficult and messy job and very hard
to be accurate.
When I do my adjusting, I do it every 90 degrees of engine rotation. I know
this is overkill as you can get away with doing it every 180 degrees. But I
use a hand-held switch that lets me crank the engine over while watching the
crank angle and just move it to approximately the 90 degree positions; eight
positions in total, then I repeat again and double check the lash. With this
procedure, I can set all the lashes to within better than 0.001". Of course,
this degree of accuracy isn't necessary with hydraulic lifters. A quarter
turn past zero lash is sufficient and also prevents lifter pump-up should
you ever over-rev and have valve float. Here is the adjustment sequence I
use:
Crank Angle Intake Exhaust
cyl. # cyl. #
TDC 8 5
90 ATDC 1 4
180 ATDC (BDC) 5 2
270 ATDC (90 ABDC) 4 6
360 ATDC (TDC) 2 3
450 ATDC (90 ATDC) 6 7
540 ATDC (BDC) 3 8
630 ATDC (90 ABDC) 7 1
TDC 8 5
I hope this table comes out legible. Note, of course, that "TDC" refers to
cylinder #1; i.e., the valves are closed. In practice, you don't have to
start at #1, just which ever #1 or #6 happens to be at TDC when you rotate
the crank to the TDC mark.
TTFN,
Bob
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