FWIW, since I had a bunch of notes on this stuff and figured it might be of interest to some others.

Ever wonder what difference all those different lash settings make when looking at solid-lifter (flat or roller) cams? Here's a list of different lash settings and how they effect the seat timing for any given cam. I'm listing the duration points at both SAE (.006" valve lift) and "actual seat" (at the point where the lash is reduced to zero) since I've seen both used.

Lash --- 1.5 Lobe Lift --- 1.6 Lobe Lift
--------- SAE (Seat) ------ SAE (Seat)
.016" --- .0147" (.0107") - .0137" (.0100")
.018" --- .0160" (.0120") - .0150" (.0112")
.020" --- .0173" (.0133") - .0162" (.0125")
.022" --- .0187" (.0147") - .0175" (.0138")
.024" --- .0200" (.0160") - .0187" (.0150")
.026" --- .0213" (.0173") - .0200" (.0163")
.026" --- .0227" (.0187") - .0212" (.0175")

Does this really make much difference? Well, if two cams both share the same advertised specs at .020" of 290* and one is designed to run at .016" lash and the other is designed for .026", the SAE duration for the tight-lash grind is likely to be 300-302* where as the looser-lash grind is going to come in around 288*. So, yeah, I'd say that 12-14* difference in seat timing is going to be pretty obvious if you compared both cams in the same engine.

How about a cam where the lash ramps have been designed to allow a fair bit of lash adjustment to allow for some tuning? Does changing the lash make much difference to what the engine sees? Here's two examples I picked up from some Cam Doctor data published years ago:

Example 1 is on an intake lobe where the lash was reduced from .018" to .014". How much extra duration resulted?
.006" - 4.6* (SAE)
.020" - 3.4*
.050" - 2.3*
.100" - 1.6*
.200" - 1.2*
.300" - 1.2*
.400" - 1.3*

Example 2 is on an exhaust lobe where the lash was increased from .022" to .028". How much less duration resulted?
.006" - 6.9* (SAE)
.020" - 5.1*
.050" - 3.4*
.100" - 2.5*
.200" - 1.9*
.300" - 1.9*
.400" - 2.2*

In both cases the biggest change in duration was right at the initial opening/closing points, but the amount of effective change tapered off significantly starting above .100" valve lift.

I also wanted to comment on what really happens when cam "designers" start mixing & matching lobe families with dramatically different designed lash specs. I had cam that spec'd out 295/305 @ .020", 265/270 @ .050", 180/178 @ .200" w/ the provided lash settings of .018" intake / .028" exhaust. Anyone want to guess what the actual duration split ended up being at those lash settings? I'll get straight to the point and say that all that additional exhaust duration got "lost" w/ the extra .010" in lash and the split ended up being negative (less exhaust duration than intake) from .020" valve lift on up.

Nice writeup Brad

Last month I went through the same thing with an MP 528 solid, at the time I concentrated on @ .050 duration and scrawled it on a piece of notebook paper. I seem to recall dropping 8 or 9 degrees @ .050 on that one between zero lash and .028.

I've read the 9 degrees @ .050 is fairly typical but haven't tried it with enough cams to say with any authority.

Ok Brad you have entirely to much time on your hands to think about all that. Ron

Most of this stuff I'd already recorded a long time ago. It was brought back to mind when I was curious how two roller cams of the same lobe family would compare if one 6* smaller at .020" / .050" / .200" was lashed at .018" vs. a 6*-larger one lashed at .026".

Just another one of those "What if... ?" things.

When trying different lash settings to fine-tune a cam, what is the most lash you would want to run? I know if you have lash caps they can get to flopping around quite a bit.

.030 is about as much as you would want.

I've been running .010 less than the card shows(hot)
for 4 years now.. thats on the intake

Not sure if any numbers under .100 change anything in power production .
I believe the minimal amount of duration shown in lash changes has less effect than the change in cam timing itself. looser means less duration tighter a bit more but it also changes valve opening points hence the powerband.

I found that running the intake lash .008 tight on a .020 spec with an increase in rocker ratio from 1.5 to 1.6 is like splitting the difference to the next size larger cam, seems to work out better with rollers