Are there typical symptoms of setting the valve lash too tight? Let's say they're tightened past one full revolution beyond zero lash. Just curious about this.

Willie

 

The factory sets them at a full turn past zero...consequence of too tight would be valve(s) hanging open.(compression loss, hard starting, etc)

You will need to run looser on performance cam grinds though.

 

Depends on the MSS. Comp recconeds 1 full turn on most of thier grinds.

 

I understand what the recommendations are. My question is what can happen if they are overtightened? Hypothetically speaking, let's take the GM's recommendation of one full turn. Instead, I'm an idiot engine builder and give each rocker two or three full turns. How would the engine run?

Willie

 

You'd have to tighten them a lot tighter than one or two extra turns to bottom them out, and only then would there be any potential for real damage.
In one of the TPIS books they did some dyno tests on lifters that were "overtightened" by up to 3 turns IIRC. And in that article, they recommended tightening them 2 turns, because it was actually better on the dyno.
I'm not sure what brand of lifters they were using, but I think that would be a factor.
I tried tightening mine 3 turns after reading that, and I didn't notice a difference. But I backed them off afterward, just cause 1 turn is recommended in my manual.

Does that help?

 

there ought to be around a tenth inch movement inside the lifter. like was said you'd need to over tighten it a lot to bottom out the cup in the lifter to cause a problem.

 

When I put my cam in I couldn't spin the motor up before tighening the rockers. So, I did the one turn thing and then they pumped up with oil and it caused the valves to hang open and it acted like it was running on 5-6 cylinders. Readjusted them and everything was good.

 

I bent 2 pushrods when I had mine overtightend.

 

so would 1/2 turn be enough or not enough for a new cam? i set mine at 1/2 turn, but haven't been able to turn the motor yet, although i'm hoping to this weekend. i can go back in and put another 1/2 turn on them now and it would be easier...

 

I take my lifters to zero lash, then go a 1/2 turn after.

 

Back to the original question:

IMO typical symptoms of rockers being too tight would probably occur at higher RPMs, when the lifters pump up, they would pump up more with a greater preload.
I'm just basing that on the concept that guys who want to run their engines at higher Rs preload the lifters less. Mebbe 1/2 turn, so they won't pump up.
I could be incorrect about this, but no one else has said anything yet, so I thought I'd put in my

 

think you need to define "overtight" i go 1/2 turn or so past zero lash so by my method 3/4 turn would be over tight and there would be no negative effects from that

 

Jeez, you guys need to loosen those rockers up! Itll wake it up performence-wise. I never run any tighter than 1/4 turn past zero lash...even with a stock cam. That is adjusted with the engine running of course.

 

i go zero lash and a maximum of 1/8 turn.i try to always go 1/16 turn but some times they make too much noise. the more you tighten them down the less lift you get.

 

If the exhaust is too tight often the headers will glow.

If the intake is too tight, it backfires up through the intake.

-- Joe

 

Ive been wondering if my rockers are too tight, they were adjusted with the engine running, tightened until they quited down and then 1 turn... the reason is low compression, i got like 90 psi from every cylinder.. but the motor doesnt smoke much and most of it is gas.. another thing im thinking of right now is bad lifters... when me and my dad installed the motor (307) hyd. lifters.. anyway it took like 30 secs of idle for some of the lifters to fully pump up. when its cold and you goose it in gear it will backfire.. but not when its warm..