What should valve lash be set at with 1.70 crower rockers

[oufan2929]

Just wanting to check over them. Thanks!--Andy

 

[1TONY1]

Just wanting to check over them. Thanks!--Andy

Ummm, -.000 ?

I think lash with solid cams....on hydraulic I like 3/4 turn after zero lash. Get zero NOT by spinning the pushrod but by rocking/ lifting the valve end of the rocker, then slightly short of 3/4 turn, lock the nut then pull the nut and the set screw just a little more to get 3/4. That really locks it tight.

Oh yea, hydraulic you can't "check" them...you have to loosen and redo. Well, technically you can check them as you loosen them (smart to do) but then comes the "redo"

 

[-FROG-]

I used my fingers to check my lash.

 

[Tagoo]

Tony, good idea on moving the actual rocker. I find it very hard to tell when I've reached zero lash by jiggling the pushrod. One related question... is it OK to adjust lash after the car has been sitting for days? Specifically, I'm wondering if the bleed-down of the lifters affects the adjustment. Although I have pre-'00 lifters in my '00 GTS (low bleed down lifters), I still worry that there may be some bleed down. If so, what is the alternative? Do I run the engine to pump up the lifters and adjust quickly before they bleed down? Or, is this simply not a concern? Thanks!

 

[Tiago]

the lifter bleed down shouldn't matter because you should only adjust the lash only when the lifter is at the base of the lobe, i.e. zero lift, i.e. the rocker is basically free at that spot.

 

[Tagoo]

Andy -
One trick I was shown to easily find when a lifter is on the base circle of the cam (for adjusting lash) is as follows:

While turning the engine over (by hand)...
Intake lifter is on the base circle when the exhaust valve first begins to open.

Exhaust lifter is on the base circle when the intake valve first starts to close.

I stick a long T-handle allen wrench in the adjuster stud that helps magnify any movement in the rocker so I can see when the rocker first starts to move.

This is for a Gen 2 engine. I would guess it is the same for Gen 3. Give me a buzz if you want me te explain in more detail.

 

[Tagoo]

Thanks Tiago,
I know it is on the base circle, but if press down on the pushrod, I can get the lifter to compress (at least that is what it feels like). Does the lifter have an internal spring or am I just causing a bleed down of the lifter when I press the pushrod into the lifter?

the lifter bleed down shouldn't matter because you should only adjust the lash only when the lifter is at the base of the lobe, i.e. zero lift, i.e. the rocker is basically free at that spot.

 

[Tiago]

there is a spring:

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[Tagoo]

Got it. Thanks! So what gets pumped up with oil on a lifter? Is it the space between the spring and the pushrod seat? If so, do you still think that if it "bleeds down" that it wont affect setting the lash?

 

[Camfab]

Man both of you have similar user names that are confusing me. Anyway Tagoo I understand exactly what your asking, and have found it annoying to find such an imprecise way of checking the preload on the lifter. Your question has nothing to do with adjusting on the base circle of the cam as this is a given. I too wonder how the bleed down effects the adjustment of the preload. I have the Mopar Preformance low bleed down lifters, I would have much preferred a solid roller cam.

 

[Greg Good Cylinder Heads]

Got it. Thanks! So what gets pumped up with oil on a lifter? Is it the space between the spring and the pushrod seat? If so, do you still think that if it "bleeds down" that it wont affect setting the lash?

The hardest part about setting the valves on a hydraulic cam is finding zero lash. I think it's easier to teach a guy how to set lash on a solid roller cam.

It doesn't matter if the lifters have bled down any or not. The spring in the lifter will force the pushrod cup against the retaining clip when pushrod is backed off.

Here's how I do it.

Do one cylinder at a time. Start at the front valve, bump the engine over until the valve you are setting is on the base circle of the cam*. Loosen the lock nut a couple of turns. With a t-handle allen wrench loosen the adjuster so you can rattle the rocker arm up and down some. Slowly turn the t-handle/adjust back in slowly with one hand and rattle the rocker with the other until you get no rattle. You'll be close to zero lash at this point. Then using your thumb and index finger spin the pushrod while moving the adjuster slightly in and out to feel where zero lash exactly is. Then you can set your preload and lock the jam nut down.

*Set the exhaust valve when the intake valve for that cylinder is at full lift. Set the intake valve when the exhaust valve for that cylinder just starts to open.

 

[Tagoo]

Thanks for chiming in Greg!!! I probably should have just called you in the first place to get a refresher on the topic.