Hello Bob,
Your valve process looks good. I'll start using it. Is this the sequence that
places the lobes opposite the lifters during adjustment? I noticed when I first
did the 427 that the lash did not come out right when using the factory system,
and I suspected it was due to the large cam overlap. I then started using the 90
degree method but adjusted each cylinders intake and exhaust when that piston
was in the TDC and firing position. Your system looks better. The info is
timely. I purchased a '66 GT350 vintage race car a couple of weeks ago and
replaced the valve springs (with the heads on) last night. I'll adjust them
tonight.
Thanks,
Craig
Bob Palmer wrote:
> 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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