What should cold lash setting be?

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Les Gibson

Les Gibson

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Good afternoon all! Got a question about valve lash settings. After running my Arrow for almost two seasons now I finally was able to get the cam card from the previous owner/engine builder. It's a Bullet cam, solid roller, 276/285 duration @ .050, gross lift .685/.682, and cam card says hot lash should be .026/.026. I'm running CNC ported W5 heads so what would the suggested cold lash setting be? I'm thinking .019? But I'm no metallurgist and not sure what the expansion rate of the metals involved would be. I have Harland Sharpe 1.5 aluminum rockers.
Also, as an interesting side note, when I bought the car the previous owner had the valves set at .018 intake and .020 exhaust which obviously isn't what the specs call for. Why do you think he deviated from the manufacturer specs?
Thank you!
 
So...if the engine is currently running. Set the lash hot as specified, then record the lash after it cools down to room temp. There is your cold spec.

Typically you can go .002 from the factory lash spec without issue. Sometimes you can go .004, even .008. You can definitely do that with a purple shaft cam. 28/32...used to run 24/28. Even ran 24/24.

Remember, while a little valve train clatter may be annoying and you may lose a few HP, a loose valve is much happier than a tight valve.
 
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Every Solid Roller that I have ever owned has wide acceleration ramp
lobes. I have run lash from .016 to .030 with no ill effects ever
last 60 years.

I sometimes move the lash around as an experiment to see of
the car wants a larger or small camshaft by how it performs
on the time slip and weather station.
 
Les Gibson said:
Good afternoon all! Got a question about valve lash settings. After running my Arrow for almost two seasons now I finally was able to get the cam card from the previous owner/engine builder. It's a Bullet cam, solid roller, 276/285 duration @ .050, gross lift .685/.682, and cam card says hot lash should be .026/.026. I'm running CNC ported W5 heads so what would the suggested cold lash setting be? I'm thinking .019? But I'm no metallurgist and not sure what the expansion rate of the metals involved would be. I have Harland Sharpe 1.5 aluminum rockers.
Also, as an interesting side note, when I bought the car the previous owner had the valves set at .018 intake and .020 exhaust which obviously isn't what the specs call for. Why do you think he deviated from the manufacturer specs?
Thank you!
Click to expand...
Don't suppose you have the LSA (lobe separation angle) to go with it? I ask because my cam (motor not together yet) is pretty close on duration and lobe lift. Thanks!

Otherwise, previous owner probably played around with lash settings looking for quicker or quieter (or just did it because they, or someone they know liked that setting and didn't think twice about it otherwise).
 
roccodart440 said:
So...if the engine is currently running. Set the lash hot as specified, then record the lash after it cols down to room temp. There is your cold spec.

Typically you can go .002 from the factory lash spec without issue. Sometimes you can go .004, even .008. You can definitely do that with a purple shaft cam. 28/32...used to run 24/28. Even ran 24/24.

Remember, while a little valve train clatter may be annoying and you may lose a few HP, a loose valve is much happier than a tight valve.
Click to expand...

I always do it the exact opposite, usually 6 or so lower when cold lower than what the cam card calls for..IE set at 20 cold if the hot lash setting is 26.
Setting cold is way more accurate. Everything is the same temp. Setting hot, you have to wait a bit just to get the covers off, then takes a while as things are cooling.
Then once set cold, let it get hot and quick check a couple, and see if your 20 cold is on the money or not. If not, adjust accordingly when it cold again. Once you know the hot/cold range( only takes once) your good.
Way, way easier to work on something when it isn’t hot. And way more accurate. If you do it cold, all are the exact same temp, no matter how long it takes you to do it.
 
Les Gibson said:
Good afternoon all! Got a question about valve lash settings. After running my Arrow for almost two seasons now I finally was able to get the cam card from the previous owner/engine builder. It's a Bullet cam, solid roller, 276/285 duration @ .050, gross lift .685/.682, and cam card says hot lash should be .026/.026. I'm running CNC ported W5 heads so what would the suggested cold lash setting be? I'm thinking .019? But I'm no metallurgist and not sure what the expansion rate of the metals involved would be. I have Harland Sharpe 1.5 aluminum rockers.
Also, as an interesting side note, when I bought the car the previous owner had the valves set at .018 intake and .020 exhaust which obviously isn't what the specs call for. Why do you think he deviated from the manufacturer specs?
Thank you!
Click to expand...
cold =.006 tighter than hot ...
 
dusterbing the peace said:
Don't suppose you have the LSA (lobe separation angle) to go with it? I ask because my cam (motor not together yet) is pretty close on duration and lobe lift. Thanks!

Otherwise, previous owner probably played around with lash settings looking for quicker or quieter (or just did it because they, or someone they know liked that setting and didn't think twice about it otherwise).
Click to expand...
LSA on the card is 106
 
B3422w5 said:
I always do it the exact opposite, usually 6 or so lower when cold lower than what the cam card calls for..IE set at 20 cold if the hot lash setting is 26.
Setting cold is way more accurate. Everything is the same temp. Setting hot, you have to wait a bit just to get the covers off, then takes a while as things are cooling.
Then once set cold, let it get hot and quick check a couple, and see if your 20 cold is on the money or not. If not, adjust accordingly when it cold again. Once you know the hot/cold range( only takes once) your good.
Way, way easier to work on something when it isn’t hot. And way more accurate. If you do it cold, all are the exact same temp, no matter how long it takes you to do it.
Click to expand...
I always set it cold, but the OP only had hot specs and wanted to know the factory cold specs.
 
Call Bullet. That’s the only right answer. He’ll give you the correct lash for your lobe.
How much your lash changes during a heat cycle you’ll have to test for.
 
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People will probably flame me. I really don't think it's that critical. As long as your pretty close and consistent. I always set them cold .004" tighter than the hot spec.
 
GTX JOHN said:
Every Solid Roller that I have ever owned has wide acceleration ramp
lobes. I have run lash from .016 to .030 with no ill effects ever
last 60 years.

I sometimes move the lash around as an experiment to see of
the car wants a larger or small camshaft by how it performs
on the time slip and weather station.
Click to expand...

This.

I wouldn’t think twice about going .006” either side of recommended.

Trying different lash is a tuning tool. IMO it would be silly to not try different lash if you are looking to get the most from your combo.
 
I think my small block is set at .012 cold. I write it on there so I Dont’s have to remember. My Keith Black 572 is .008 cold. Aluminum block aluminum heads. If you go .006 tighter cold like you said in your first post you’ll be fine. Then if you’re curious sometime down the road you can check one hot.
 
pittsburghracer said:
I think my small block is set at .012 cold. I write it on there so I Dont’s have to remember. My Keith Black 572 is .008 cold. Aluminum block aluminum heads. If you go .006 tighter cold like you said in your first post you’ll be fine. Then if you’re curious sometime down the road you can check one hot.
Click to expand...


I’ve done all aluminum blower stuff that lashed at .004 cold that was .020 hot.
 
roccodart440 said:
So...if the engine is currently running. Set the lash hot as specified, then record the lash after it cools down to room temp. There is your cold spec.

Typically you can go .002 from the factory lash spec without issue. Sometimes you can go .004, even .008. You can definitely do that with a purple shaft cam. 28/32...used to run 24/28. Even ran 24/24.

Remember, while a little valve train clatter may be annoying and you may lose a few HP, a loose valve is much happier than a tight valve.
Click to expand...
Respectfully, it's the other way around. It's better to have a more gentle ramp than to hit it at a steeper than designed point. I'll always start tight and at the most I'll go .002 looser. But again as has been mentioned, it's a tuning technique.
 
during the last few Dyno pulls we tried tightening the lash to see what my engine liked, I think I ended up tightening the lash .006 - .008 on both intake and exhaust and it picked up power.
Not a big gain but it was around 8-10 HP.
I would have liked to do more tuning but I was already around 25 pulls.
 
ValiantS said:
Respectfully, it's the other way around. It's better to have a more gentle ramp than to hit it at a steeper than designed point. I'll always start tight and at the most I'll go .002 looser. But again as has been mentioned, it's a tuning technique.
Click to expand...
I would never advocate going looser.

The point of my statement was as follows; Too much lash is better than too little lash, or no lash.
 
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