Cold valve lash settings - tighter or looser?

[FishFry]

just saw that video, and it got me thinking - have I done it wrong all those years?
It goes against anything I learned, but the proof seems to be in the pudding.

https://youtu.be/V8liNwa-NEI

Common sense tells me that the pushrods/valves extend when they get hot, but I guess the block, the head and the rocker stands expand much more than the pushrods, valves and lifters etc.

Frank

[mag2555]

I did not watch the video, but from what must be 30+ years ago now I found that with Aluminum heads and cams that need lash you go .006” to .008” tighter then needed spec once the head has got up to a evened out normal running temp.

[1980RS]

The aluminum settings are right in the video but the cast iron head cast iron block cold settings are wrong. I have always used .002 looser with the cast iron stuff and have tested cold vs hot and it was spot on every time. For years I set a couple of my aluminum heads wrong as a racer told me the opposite when setting cold. I did not realized that until I had beat the crap out of a set of valve tips that he was wrong. So I did my homework and got settings for cold right from Dart Machinery talking with them at a show one day.

[CamKing]

With aluminum heads and/or block, the lash is going to grow, as the engine gets hot. How much growth, depends on the rest of the valve-train.
With iron heads and block, the lash will either grow or shrink a small amount, as the engine gets hot. It depends on how much growth you get in the rest of the valve-train.

That's why you always need to set the lash, with the engine hot.

If you're run an iron/iron engine, set the cold lash .002"-.003" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

If you're run an iron/aluminum engine, set the cold lash .006"-.007" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

If you're run an aluminum/aluminum engine, set the cold lash .014"-.016" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

[ClassAct]

With aluminum heads and/or block, the lash is going to grow, as the engine gets hot. How much growth, depends on the rest of the valve-train.
With iron heads and block, the lash will either grow or shrink a small amount, as the engine gets hot. It depends on how much growth you get in the rest of the valve-train.

That's why you always need to set the lash, with the engine hot.

If you're run an iron/iron engine, set the cold lash .002"-.003" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

If you're run an iron/aluminum engine, set the cold lash .006"-.007" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

If you're run an aluminum/aluminum engine, set the cold lash .014"-.016" tighter then the recommended hot lash, then run the engine until it's up to temp, and shut it off, and quickly set the valve on one cylinder to the recommended hot lash settings. Let the engine fully cool down, then measure the lash on the cylinder you set hot, and those measurements are now your "Cold Lash" settings, and should be used to re-set the other cylinders lash while the engine is cold.

Exactly. I’ve never seen an iron/iron engine lose lash with heat. Ever. Guys setting them loose cold are just beating the valve train up.

[HQM383]

SBC, iron block, aluminum heads.
I’ve set hot @ .018”.
Checked cold for reference- .012”

[DCal]

I didn't see aluminum heads and iron block or I misunderstood, when I ran Arias hemi alloy heads on an iron block I think it was .012 but that was a much larger unit than a SBC which is what I'm interested now.

[Racing68]

A few that I remember over the years are. BB Chevy stock cast iron 454 block and oval port heads solid roller cam was the same hot and cold. SB Chevy Dart block and 18 deg dart heads solid roller cam was .007 tighter cold. BB Chrysler Indy aluminum short deck block and solid cast aluminum 440-1 heads solid roller cam were .022 tighter cold.

[Walter R. Malik]

I have built some all aluminum big block Chevy engines where after setting lash hot, the engine wouldn't even start when cold because there was no lash at all. So, the hot lash had to be made a bit looser in order for the valves to even seal when cold.

[In-Tech]

I have built some all aluminum big block Chevy engines where after setting lash hot, the engine wouldn't even start when cold because there was no lash at all. So, the hot lash had to be made a bit looser in order for the valves to even seal when cold.

Plenty of times we had block and oil heaters to solve that.

[CamKing]

I have built some all aluminum big block Chevy engines where after setting lash hot, the engine wouldn't even start when cold because there was no lash at all. So, the hot lash had to be made a bit looser in order for the valves to even seal when cold.

Plenty of times we had block and oil heaters to solve that.

Yep, I designed a cam for the Daytona Prototype class, that powered the 2004 24 hours of Daytona winner.
At that time, there was a maximum gross valve lift rule, so I designed the cam to that maximum gross valve lift, but designed the lash ramp for a .010" hot valve lash. This gave it more net valve lift, then if I designed it for .020"+ hot valve lash.
The only issue was the engine was an aluminum block with aluminum heads, so the only way they could start the engine, was to pre-heat the oil and block. The owner of the car complained about all that extra work, but after winning Daytona, he stopped complaining.

[chevyart]

i always went with .002 looser than mfg specs cold with steel heads. always went with .004 tighter with Aluminum heads and had heard to go tighter .010 with aluminum heads and block combined(never got to that one). if not sure of this it would be simple to adjust the valves hot to mfg. specs and then check what the settings end up as with the engine completely cooled off(like a reverse engineering).. to do the valves adjustment hot you will probably need to do one side while hot and then restart the engine to get it fully hot to do the other side. just my take on this subject. Art in NY

[Walter R. Malik]

I have built some all aluminum big block Chevy engines where after setting lash hot, the engine wouldn't even start when cold because there was no lash at all. So, the hot lash had to be made a bit looser in order for the valves to even seal when cold.

Plenty of times we had block and oil heaters to solve that.

Yep, I designed a cam for the Daytona Prototype class, that powered the 2004 24 hours of Daytona winner.
At that time, there was a maximum gross valve lift rule, so I designed the cam to that maximum gross valve lift, but designed the lash ramp for a .010" hot valve lash. This gave it more net valve lift, then if I designed it for .020"+ hot valve lash.
The only issue was the engine was an aluminum block with aluminum heads, so the only way they could start the engine, was to pre-heat the oil and block. The owner of the car complained about all that extra work, but after winning Daytona, he stopped complaining.

The engines I am talking about were "Cigarette" style race boat engines. The hottest water temp they ever got were about 140 or less ... lol.

This was almost 30 years ago and I remember opening the last from .012" to .016" ... those engines never had any valve train issues; the Crower solid flat tappet camshafts were probably not of the aggressive ramp style.

[CamKing]

i always went with .002 looser than mfg specs cold with steel heads. always went with .004 tighter with Aluminum heads and had heard to go tighter .010 with aluminum heads and block combined(never got to that one). if not sure of this it would be simple to adjust the valves hot to mfg. specs and then check what the settings end up as with the engine completely cooled off(like a reverse engineering).. to do the valves adjustment hot you will probably need to do one side while hot and then restart the engine to get it fully hot to do the other side. just my take on this subject. Art in NY

You only need to set the valves on one cylinder, hot.
Then when it cools all the way down, measure the lash on that one cylinder, and that will be the cold lash settings on all the cylinders.

[FishFry]

So the consensus is:

Steel : lash gets tighter when hot
Aluminum: lash gets wider when hot

Right?

Frank