Magnum 282 solid, 282 adv, 236 at 50, .495 stock lift, .528 with my 1.6 rocker arms.

It is said that you can tighten lash to see if the engine likes it.

Question is how much can you safely tighten it? Magnum Cams must have a mild ramp speed.

None in my opinion, I'd run what ever lash the cam card say's. I wouldn't deveate anymore than .005" from the proper lash.

Generally, you can tighten them up as much as you want but making sure that the valve is closing. You probably don't want to go that far. However, loosening them is a bit different. The looser they get, the harder the cam slaps the lifter after the lash is taken-up. One of the cam manufactures recommends no more than 0.004" looser than spec for their agressive lobes, FWIW. I've run as loose as 0.034" on a 0.026" spec.on an old style cam. Ran well, but sounded like a tin can of marbles.

If I am remembering correctly,the Magnum lobes were designed so you can vary the lash more than most. I think they used to tell you anywhere from .020 to .035 was okay. I will have to check and get back to you before you go too far.
Keith

Rule of thumb, .004"-.005" variation from spec. Agree it depends on the lobes. My tight lash fast rate cam probably would be on the low side of tolerence for variation. If you vary much, everything needs to be "right" including measurement technique to prevent a big "oops".

??? I ran a MP 528 solid at 22-24 (cold). It seemed to run better than the factory recommened 28-32

I run the MP 528 cam and set the lash 20/22 cold. I run Stealth heads so the lash gets bigger as the engine warms up. I don't think I'd set the lash that tight with iron heads because the lash gets smaller with heat. 28/32 cold with iron heads would be around 26/30 with iron heads once it's warm and that's about what I have when the ally heads heat up.

You want to increase the lash on a 1.6 rocker versus a 1.5 anyway. I imagine the engine would "like" any decrease in lash since that is essentially increasing lift and duration. Personally I'd run what the manufacturer recommends and if you want more power, find it somewhere else.

I have always thought "tight lash" cams were just another way to claim better numbers under the curve. Another cam sales device for sure! ( or every cam on the planet would be one!) I have seen race engines run and sound just fine but be much slower( several tenths) when lash was too tight--as in the valves never really close and "seal in" that lick. You have to get enough lash so that they really have a chance to close at the RPM you are racing at. I would bet my shop that on a dyno you would see very little diff going with more lash but too little can kill power. It is all bout RPM as well--a street engine is not the same as a unit buzzing 7500 RPM--Component weight plays even more as RPM goes up--Swapping to Titanium retainers can often make it feel like you changed engines in a drag car--If you were short on installed height like some small blocks even more so. It is a balancing act and lash plays a very small part as long as you have enough. There is no way to explain how much you can learn on a dyno in a year--it will dispell lots of BS "conventional wisdom" in a HURRY.
Light weight valvetrain GOOD, Belt Drives GOOD, stiff pushrods GOOD, enough spring pressure to control it all GOOD Chasing valve lash all over the place--a waste of time IMO. I have seen Bob Reed lash a Hemi in staging so fast it would make your head spin and he did NOT get them within a few thou--he lashed 'em and raced 'em--in other words--made darn sure it HAD some then went to it!!! Ya'll should to--and...in a drag engine do intake and Ex the same--it is EASIER and who thinks that in 6-10 seconds an ex valve will be hot enough to change the lash enough to make one millionth of a second diff?