Valve lash

[GoMangoBoys]

When we built the engine, we started with a lighter valve spring.  After breaking in the cam, we are changing to the heavier spring that was recommended by the cam manufacturer, Hughes Engines.  If we had previously adjusted the valve lash, do we need to readjust them valve lash after changing the valve springs? The rocker shaft, rockers caps, shims and pushrod all went back on exactly as they came off prior to swapping the springs.

[Chryco Psycho]

I would , as the cam breaks in I have found 2-3 adjustments are nessisary over the first 1000 miles or so , then everything seems to become stable .

[Spikedog08]

How often is it needed once broke in?   Ever year?   

[MoparLeo]

It depends on a lot of things. How high do you rev the engine ? How hard is your driving style ? Daily driver ?Aluminum heads ? Etc...
You will just need to come up with your own maintenance schedule.. I would check it based on time first. weekly, monthly..If it needs adjustment each time you do it weekly. If not maybe monthly, bi-monthly.
That is the main problem with solid cams. Takes more time and money.
Just like some chicks are high maintenance, same difference.

[rikkitik]

 I would, and I have always done so after reinstalling the inners on mine (regardless of which engine).
For me, it's just not worth the worry of, "should I have checked the adjustment?", after the fact. I want to KNOW they're "right".

[Spikedog08]

Ok so how do you figure what to lash the valves at?  I'm told there is a lot of criteria to consider when determining the gap on the lash?  Thoughts?

[MoparLeo]

Some manufacturers say cold and some say hot. Depends on the company and their cams.

[Chryco Psycho]

If you still have the cam card it will state what the lash is on there , Most Lunati cms are .016  intake & ,020 exhaust

[rikkitik]

 I like to run mine where they're relatively quiet but "safe", which is usually about .016, hot (with my current cam, as well as a couple others).
Aluminum heads grow, which opens up clearance, but the exhaust valves grow too which tightens up clearance. So I use the method that Jim Jones (Traco Engineering fame) explained to me.
Bring the engine up to temp. Shut it off, pull all but a couple lower cover bolts, start it up and run it. Shut it off, and pop a valve cover off, set one cylinder while it's still hot. Replace the cover, start it again. Shut it off, pull the other cover, set one cylinder while it's still hot.
Let the engine sit overnight and cool off. Check the two cylinders you set while they were hot. You will then learn the correct cold setting that translates to the "hot" setting.
You only need to do this one time for a "given" (head, cam, valvetrain) combination.

[Spikedog08]

If you still have the cam card it will state what the lash is on there , Most Lunati cms are .016  intake & ,020 exhaust

I have everything that the engine builder gave me but no cam card.  Didn't know you would have different for intake and exhaust . .

[RUNCHARGER]

Anytime you pull the rocker gear you should check valve lash with adjustable rockers. Then I will recheck within a week. On a hobby car I like to check lash and have a quick look for anything developing twice a year. When I check lash I also use a light and look at every cam lobe etc. looking for wear patterns and trash.

[Chryco Psycho]

The exhaust valves hangs open in the hot exhaust so is subject to far more heat so extra clearance is normal .

[MoparCarGuy]

This is why they created hydraulic roller camshafts. Performance similar to a solid tappet with less maintenance like a standard hydraulic lifter.

[Chryco Psycho]

But the ramp speeds are slower as the lifter will collapse with the  needed spring loads .

[rikkitik]

 Strongly agree with Chryco on this.
Today's HR lifters are high bleed (squishy) and lose a lot of the ramp advantages of a roller. Few HR cams are as "quick" as a well designed .904 SFT, and the .200 duration suffers.
Add to that the current "state" of hydraulics in general, and cam selection these days becomes a real "crap" shoot.