For those that have an aluminum block, how much tighter do you set your valve lash cold vs hot?

.013"-.014". This is on my KB block hemi.

You set them that much tighter, or to those numbers?

That much tighter. I usually set them at .008" lash cold.

We run Aluminum block and heads and set lash .013-.014 tighter than specs on cam card So on our application the spec is .018 cold so we set them .005 cold.

See Jeff...I'm not crazy!

We set ours .012" tighter than the cam card. Near enough what everyone else does. It's a wedge motor, Hemi heads might "grow" more due to the size of them but that's just a guess. We've checked it hot and the lash grows to what the card calls for (.024") perfectly. KB block, Indy 572-13 heads and Jesel rockers BTW

I set mine at .005 cold, too. That gave me about .023 or so hot when the cam card called out .020. But even the .005 was relative to 60+ temps.

Did anyone else see the EngineMasters episode the other night where they were playing around with different lashes? They picked up some noticeable ponies with a looser intake lash. Changing the exhaust both ways did little to nothing. Of course this was on a big block Shivvy, so.......... Still, it was interesting.

Just don’t go crazy and start reving it up to 7000 rpm on start up.

Jeff Crane says Aluminum block and heads subtract .012" Iron block Al. heads subtract .006" Iron block and heads add .002"

But that's just a safe beginning. Like most others here I set mine tighter than that. Instead of the .006 they suggest I set mine at .012" cold to get the .020" I need on my al. heads.

You have to test each motor, not all of them will be the same.
Set them cold and then warm up the motor so you get around 160 F oil temps and pull one valve cover and check one set of valves to see what your motor needs Write it down also

My experience with my BMP aluminum block, B1 heads, and 1.7 rocker ratio is the same. (180 to 70 deg)

Details:
Taller head (deck to rocker shaft) will expand more than shorter head (Edelbrock RPM).
Rocker ratio changes it a little, est 1.5 ratio using 0.012" changing to 1.7 ratio (1.7/1.5)x0.012 = 0.0136"
Difference between Cold and Hot temps changes lash. I use 0.00013" per degree temperature change.
50 deg F, 0.006" lash
70 deg F, 0.008" lash. (70-50) x0.00013 = 0.0026 lash change
180 deg, 0.023" lash. (180-50)x0.00013 = 0.017 lash change
200 deg, 0.026" lash. (200-50)x0.00013 = 0.020 lash change

Thanks for the advice everyone.

Struggling a little with the #6 rockers, as the roller isn't aligned with the valve tip. Some reason it's only a problem with that set of rockers. Spacers need to be shaved down some to make everything line up in the right spot.

FWIW I have run aluminum blocks for well over a decade and it will end up being between .013"-.020" cold. Most of mine have ended up .014-.016" in growth. My numbers are from low deck and tall deck KB's, Indys and World blocks FWIW

Setting my low deck Indymaxx block at 0.016 cold moves to 0.024 hot.

setting my Indy block with Trick Flow heads and Harland Sharpe rockers at .010 cold nets .026 hot. Birdtracker