valve lash and power gains/losses

So, got my cam and heads in. Broke in the cam, drove it for a couple days. Had set the valve preload cold at 1/2 turn past zero lash. Running great, lots more power. Was a little unsure of where I had set preload , so asked on here. Realized I had maybe set it a bit tight, so pulled the valve covers and set everything at 1/4 turn past zero. Engine seems to have lost a bit of power and wondering if it could be my valve lash? Doesn't make a lot of sense to me, because it seems like the lifters would just pump up more? Or no, and I maybe lost some valve lift? Here's where it gets gray for me, as I don't have a very good understanding of how that works. Any insights would be great.

78ranger wrote:So, got my cam and heads in. Broke in the cam, drove it for a couple days. Had set the valve preload cold at 1/2 turn past zero lash. Running great, lots more power. Was a little unsure of where I had set preload , so asked on here. Realized I had maybe set it a bit tight, so pulled the valve covers and set everything at 1/4 turn past zero. Engine seems to have lost a bit of power and wondering if it could be my valve lash? Doesn't make a lot of sense to me, because it seems like the lifters would just pump up more? Or no, and I maybe lost some valve lift? Here's where it gets gray for me, as I don't have a very good understanding of how that works. Any insights would be great.

There is not a lot to be gained on a non adjustable valve terrain through valve lash, some can be lost but it will either be happy/unhappy/hurt. If it ran good with 0 + 1/2 turn leave it there...too tight = broken parts, too loose = loss of power and potentially broken parts, the thing to remember is that it is a NON adjustable valve terrain. Consider it as the lifters are teaching you how to adjust and be comfortable with a valve terrain with less costly mistakes.JMO

I guess misleading wording on my part, it is an adjustable valve train. Lash/ preload .

78ranger wrote:I guess misleading wording on my part, it is an adjustable valve train. Lash/ preload .

No you were not misleading, and yes you have to adjust the valve terrain with preload on the lifter, but a truly adjustable valve terrain you do not feel the resistance on the pushrod and add some preload to the lifter, you set the valve at the same timing event with a feeler gauge to give a specific valve lash or clearance between the tip of the rocker arm and the tip of the valve you are adjusting, unlike a positive stop rocker arm you are adjusting the preload, but it is a hydraulic not an adjustable valve terrain.

Spin motor over till the rocker arm is on the back side of the cam lobe. now run the rocker down to zero lash now turn it a 1/2 turn and spin the pushrod with your finger tips if it spins it will be good. lock it down right there

It's pretty simple just take your time if your not sure turn the motor again until you feel the rocker open and close then your getting close to backside of the cam lobe

So, do you have a solid or hydraulic cam? Solid you use a feeler gauge, hydraulic you give it a certain amount more turns after zero lash.

Jess

Hydraulic. And thanks everybody for the replies. I think I've got the adjustment down. Was just curious about the loss of power with a difference of only a quarter turn or so. Set it at 1/2 turn past zero and it really picked back up. Will probably go a smidge tighter? And see what it does. Mostly just trying to educate myself a little. From what I've been able to find, 3/4 is about as far as you want to go? Was just surprised at the difference. As always, thanks again everybody.

I have always set my hydraulic lifter preload to +1/2 turn without issue. I would rather have a little more preload than risk them getting loose. I'm not really sure why you lost power, but obviously 1/2 turn works better in your situation. I doubt 3/4 turn will do anything, other than just cure your curiosity. If it does make a difference, post back here because now I'm curious.

if you have aluminum heads might want to adjust either way to compensate for the head moving away from the block as it heats up. the solid roller guys tend to tighten up the lash a little with alum heads

gmsmkr wrote:Spin motor over till the rocker arm is on the back side of the cam lobe. now run the rocker down to zero lash now turn it a 1/2 turn and spin the pushrod with your finger tips if it spins it will be good.  lock it down right there

It's pretty simple just take your time if your not sure turn the motor again until you feel the rocker open and close then your getting close to backside of the cam lobe

^^^^^^^^^This^^^^^^^^^^

78ranger wrote:Hydraulic. And thanks everybody for the replies. I think I've got the adjustment down. Was just curious about the loss of power with a difference of only a quarter turn or so. Set it at 1/2 turn past zero and it really picked back up. Will probably go a smidge tighter? And see what it does. Mostly just trying to educate myself a little. From what I've been able to find, 3/4 is about as far as you want to go? Was just surprised at the difference. As always, thanks again everybody.

Just bare in mind that is smidge is not an exact science and too tight will likely kill lifters, or bend pushrods as I mentioned earlier happy/unhappy/hurt if you are looking for major gains change the camshaft.

gmsmkr wrote:Spin motor over till the rocker arm is on the back side of the cam lobe. now run the rocker down to zero lash now turn it a 1/2 turn and spin the pushrod with your finger tips if it spins it will be good.  lock it down right there

It's pretty simple just take your time if your not sure turn the motor again until you feel the rocker open and close then your getting close to backside of the cam lobe

Just to clarify, once you have that specific cam lobe on it's base circle (search the EOIC method for valve lash adjustment), that's when you can adjust that particular pre-load (as you stated). However, when setting preload, you loosen the rocker arm and turn out the set screw on the poly-lock a couple turns. Then spin the pushrod back and forth with your finger tips on one hand while tightening the nut for rocker arm with your other hand. AS SOON AS you feel slight drag on the pushrod (zero lash), STOP, grab a wrench, and tighten the rocker 1/2 turn further and lock your set screw while being sure not to let the nut turn. It will be difficult to spin the pushrod once the lifter is preloaded, especially if there is oil on your fingers.
The way you stated it made it sound like the pushrod would freely spin when preloaded, while this is not the case.
I think the OP understands this process, I just wanted to clarify for anyone else who might read this.