Valve lash settings

Lostnwalmart

Lostnwalmart

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So here lately I have been doing a few guys post up questions about valve lash. I have always believed tighter is better. It will start opening the valve sooner and closing it later but peak lift will stay the same. I run .008in and .015ex. Stock calls for .010 and .020. I noticed faster spool up and the truck idles quieter. Now this is what I recamend on a stock cam and it seems to work great on my 181/210 Hamilton cam also.

What do the rest of you run your lash at what is to tight? (assuming nondecked head or block and a stock thickness head gasket) I have been thinking about dropping mine down to .012 ex to help spool a little more. Thoughts?
 
I run 8 and 16 but I saw somebody running 5 and 10 and having good luck. By running .008 instead of .010 wouldn't your valve lift increase by .002?

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It only allows the valve to open sooner peak lift will not change but the valve will be open longer. It increases the duration of lift when the cam is pressing up on the pushrod/rocker there is no longer lash.
 
Lostnwalmart said:
It only allows the valve to open sooner peak lift will not change but the valve will be open longer. It increases the duration of lift when the cam is pressing up on the pushrod/rocker there is no longer lash.
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But you're taking up .002 of airspace that would just be wasted with the stock setting. If the lobe lift is .300 its only going to lift the rocker .290 because it has to take up the lash space before it lifts the valve. Im not saying you're wrong im just saying that im not visualizing how im not right. Maybe after I sleep on it lol.

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Valve lash

Open the lash up and it will make more power. When you open up the lash you are into a later part off the ramp on the cam. It is harder on the valvetrain but will run better. Jeff
 
Could you please explain how having the valve open less creates more power? Does it have to do with changing the lsa? Educate me :Cheer:
 
Lobe separation angle does not change at all. Think about it; once the cam is ground the only way the LSA can change is if you regrind another. (maybe a cam already ground can be changed, not really sure) But what Stingpuller is talking about, I too am curious.
 
.007/.012 for me. I noticed quicker spool as well, not drastic, but noticeable. Tighter lash makes the cam duration AND PEAK LIFT go up. Erik Koenig instructor at School of Automotive Machinists and I have discussed this many times during my previous super silly .769" lift solid roller street motor and tighter breaks less parts and is generally better. Our discussions pertained to mainly solid roller setups but these big mushroom lifters seem to afford many of the same durability advantages.
 
Nick expliain to me how peak lift goes up? In my head once that lash is taken up (the valve opening) all the lash is taken up it's just moving sooner not higher.

Red I was thinking cam duration and lsa are similar right? It of course won't change the cam but it will change how the valves act.
 
A while back I went from 10 & 20 to 8 & 18. Noticed a difference on the low end and noise. On a stock cam and stock springs I'm not comfortable going much lower until I learn something new.
 
Lostnwalmart said:
Nick expliain to me how peak lift goes up? In my head once that lash is taken up (the valve opening) all the lash is taken up it's just moving sooner not higher.
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Think of it this way. In tightening the lash you close the distance between the valve stem and rocker tip, no duh right. For simplification the valve stem and lifter move in a linear fashion, pretty much up and down (without including any small amount of deflection which may be present). The rocker arm multiplies the lift transmitted to it from the lifter to the valve stem, in the case of the 12v by 1.7 given their 1.7 ratio rockers. If you close the gap between the valve stem and rocker tip you are transmitting more of the up and down motion of the lifter into the valve stem. If you have .200" lash no matter where the lifter is on the lobe of the cam be it at peak lift, the opening, or closing ramp, you would be missing .200" of lift at the valve. Now if you have .010" lash you will only be missing that .010" at any point not just when the lash is taken up or released but also at peak lift.

Think of it in terms of elevation. If you are traveling on flat land at an elevation of 30 feet above mean sea level and you reach the peak of a hill in your path which happens to be at 100 feet above mean sea level you have just experienced a 70 foot elevation change. Think of the 70 foot as the lift transmitted into the rocker arm in turn multiplied by the ratio of the rocker in a linear fashion. Now consider if you are traveling on a lower elevation section of flat land such as 10 foot above mean sea level yet still cross the same hill with a peak of 100 feet above mean sea level. You just experienced a 90 foot elevation change. Consider the flat land as lash with the higher elevation flat land representing the looser lash setting and the lower elevation flat land representing the tighter lash setting. The hill is the peak of the lobe of the camshaft and does not change when discussing different lash settings on the same cam.
 
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Lostnwalmart said:
Nick expliain to me how peak lift goes up? In my head once that lash is taken up (the valve opening) all the lash is taken up it's just moving sooner not higher.

Red I was thinking cam duration and lsa are similar right? It of course won't change the cam but it will change how the valves act.
Click to expand...

When you tighten the lash, you add length via the adjusting screw. This effectively makes the pushrods longer.
 
NickTF said:
Think of it this way. In tightening the lash you close the distance between the valve stem and rocker tip, no duh right. For simplification the valve stem and lifter move in a linear fashion, pretty much up and down (without including any small amount of deflection which may be present). The rocker arm multiplies the lift transmitted to it from the lifter to the valve stem, in the case of the 12v by 1.7 given their 1.7 ratio rockers. If you close the gap between the valve stem and rocker tip you are transmitting more of the up and down motion of the lifter into the valve stem. If you have .200" lash no matter where the lifter is on the lobe of the cam be it at peak lift, the opening, or closing ramp, you would be missing .200" of lift at the valve. Now if you have .010" lash you will only be missing that .010" at any point not just when the lash is taken up or released but also at peak lift.
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I was sitting here thinking about it and about to ask if it changed the rocker ratio LOL very good info!
 
Lostnwalmart said:
I was sitting here thinking about it and about to ask if it changed the rocker ratio LOL very good info!
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I added a bit since this quote. Rocker ratio does different things as well. Increasing rocker ratio fattens duration everywhere in addition to adds more lift. The common idea that rocker ratio increases only peak lift are wrong. A simple excel sheet will debunk that common idea.

Here you go, from an old post in the for sale section:

Actually increased ratio will make your cam bigger slightly but not much. The difference grows larger at all lift points with a higher ratio.

lobe lift 1.7 1.8 diff
0.2 0.34 0.36 0.02
0.21 0.357 0.378 0.021
0.22 0.374 0.396 0.022
0.23 0.391 0.414 0.023
0.24 0.408 0.432 0.024
0.25 0.425 0.45 0.025
0.26 0.442 0.468 0.026
0.27 0.459 0.486 0.027
0.28 0.476 0.504 0.028
0.29 0.493 0.522 0.029
0.3 0.51 0.54 0.03
0.31 0.527 0.558 0.031
0.32 0.544 0.576 0.032
0.33 0.561 0.594 0.033
0.34 0.578 0.612 0.034
0.35 0.595 0.63 0.035
0.36 0.612 0.648 0.036
0.37 0.629 0.666 0.037
 
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Wow it's made it to 16 posts without going to hell! That's a new record
Nick again great info there are alot of little things that can be done to these engines to get them running just a little better.
 
Lostnwalmart said:
Wow it's made it to 16 posts without going to hell! That's a new record
Nick again great info there are alot of little things that can be done to these engines to get them running just a little better.
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Valve trains are highly complex beasts. These motors operating in such low rpm environments relatively speaking make things easier I think but they have their own issues such as silly high opening efforts associated with the exhaust valve and all that cylinder pressure. There are many things which won't show up anywhere other than in real life no matter how sound on paper.

A story that forever stuck with me was when speaking with one of the higher ups at Crane Cams. A drag racer was having problems loosing a ton of e.t. Come to find out the issue at hand was the particular rpm he was doing his burnout in was causing harmonices in the valve springs superheating them and turning them into jello going down the race track. A simple increase in burnout rpm to get the valve springs out of that harmonic took care of the problem. Good luck finding that one out on paper when figuring out if a spring will go into coil bind with your desired cam lol.
 
Lostnwalmart said:
Red I was thinking cam duration and lsa are similar right? It of course won't change the cam but it will change how the valves act.
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Meh, couldn't tell you now. After reading everything the other Nick posted I'll just keep my mouth shut and read.

When I put a cam in my car I did hours and hours or reading and searching. $hit, I had to do separate reading and research just to learn all the abbreviations. Plus a local engine builder really helped me understand them more in depth... But their is always more to learn. Good info in this thread.:rockwoot:
 
Lostnwalmart said:
Could you please explain how having the valve open less creates more power? Does it have to do with changing the lsa? Educate me :Cheer:
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The later the valve opens the more cylinder pressure can be made
 
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