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> Valve clearance with Chrome Moly Pushrods, Please confirm the clearance is to be ZERO
jjs3rd914
post Aug 22 2018, 09:07 AM
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Finishing a 2056 build with new 2L head castings, new WebCam cam, etc. Valve geometry done and SAT, so have custom lenght new Chrome Moly push rods. From all the searches it seems the consensus is zero valve clearance with these push rods and we also installed new genuine 911 swivel feet adjusters.

Can we get a general consensus to confirm ZERO running valve clearance is preferred?

or

IF not what is the recommended clearance?
Thanks

jjs3rd914
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76-914
post Aug 22 2018, 09:13 AM
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"0" clearance (IMG:style_emoticons/default/beerchug.gif)
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ClayPerrine
post Aug 22 2018, 10:51 AM
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Adjust the valves so that you can turn the swivel foot with a slight drag.

That's it. No feeler gauge required.
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VaccaRabite
post Aug 22 2018, 10:53 AM
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What they said.
Set it to zero. No feeler gauge. Just turn it in till it JUST touches and tighten the locking nut.

Zach
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Mark Henry
post Aug 22 2018, 11:29 AM
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(IMG:style_emoticons/default/agree.gif) Zero,
The big thing to watch for is once done the PR should still be able to spin easy.
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iankarr
post Aug 22 2018, 12:42 PM
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Yep. Someone once called it “loose zero” which seems like the perfect description.
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jjs3rd914
post Aug 22 2018, 01:16 PM
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QUOTE(cuddy_k @ Aug 22 2018, 10:42 AM) *

Yep. Someone once called it “loose zero” which seems like the perfect description.


THANKS for all the verification replies, a. Loose Zero. It is!

jjs3rd914
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worn
post Aug 22 2018, 01:20 PM
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QUOTE(Mark Henry @ Aug 22 2018, 10:29 AM) *

(IMG:style_emoticons/default/agree.gif) Zero,
The big thing to watch for is once done the PR should still be able to spin easy.


How bad a thing is it to set them to stock? I mean beyond that tappet sound?
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Mark Henry
post Aug 22 2018, 02:28 PM
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QUOTE(worn @ Aug 22 2018, 03:20 PM) *

QUOTE(Mark Henry @ Aug 22 2018, 10:29 AM) *

(IMG:style_emoticons/default/agree.gif) Zero,
The big thing to watch for is once done the PR should still be able to spin easy.


How bad a thing is it to set them to stock? I mean beyond that tappet sound?

Just noise, rattle, quite loud compared to aluminum PR's.

I've been doing zero for years with no ill effects, I used to run .004 but going to zero was a big difference.
Both T1 and T4.
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bbrock
post Aug 22 2018, 03:30 PM
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So how does the noise compare between aluminum PRs at stock clearance vs. chrome moly at zero clearance? It's a question I've been wanting to ask. This seemed like a good time.
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jtprettyman
post Aug 22 2018, 03:42 PM
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QUOTE(cuddy_k @ Aug 22 2018, 01:42 PM) *

Yep. Someone once called it “loose zero” which seems like the perfect description.

Sounds like a girl I knew in high school......
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Mark Henry
post Aug 22 2018, 04:11 PM
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QUOTE(bbrock @ Aug 22 2018, 05:30 PM) *

So how does the noise compare between aluminum PRs at stock clearance vs. chrome moly at zero clearance? It's a question I've been wanting to ask. This seemed like a good time.

Definitely noisier, not too bad though, price you pay for performance cam.
Head work, heavier than stock springs, cam, etc., in my book CrMo pushrods are a must.
I only use quality Manton PR's.

There's no reason to use steel push rods on a stock engine.
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Jetsetsurfshop
post Aug 22 2018, 05:53 PM
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Isn't there a requirement from Webcam for the valve lash?
(IMG:style_emoticons/default/poke.gif)
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VaccaRabite
post Aug 22 2018, 09:45 PM
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QUOTE(Jetsetsurfshop @ Aug 22 2018, 07:53 PM) *

Isn't there a requirement from Webcam for the valve lash?
(IMG:style_emoticons/default/poke.gif)

Yes. But that’s intended for stock aluminum pushrods. They heat up and expand and will keep valves from closing all the way.
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euro911
post Aug 23 2018, 12:24 AM
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Another term often used is 'zero lash'
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Jetsetsurfshop
post Aug 24 2018, 10:15 AM
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Anyone have a picture of the camshaft after running zero lash? I'm having a hard time with this spec. (IMG:style_emoticons/default/huh.gif)
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euro911
post Aug 24 2018, 11:05 AM
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Read this: https://www.dragzine.com/tech-stories/how-t...ash-like-a-pro/
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HAM Inc
post Aug 24 2018, 11:53 AM
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QUOTE(Jetsetsurfshop @ Aug 24 2018, 09:15 AM) *

Anyone have a picture of the camshaft after running zero lash? I'm having a hard time with this spec. (IMG:style_emoticons/default/huh.gif)


Shane, I don't have pictures of cam wear when running zero lash, but I have pictures of valve seats and retainers that ran with excessive lash. That ticking sound you hear with loose valves is the valve train hammering itself. Do that at high revs on a race engine and the sound, if you could hear it, would be of the valve train beating itself to death.

The cam won't wear more because of a starting lash of zero and you can always check the lash with the engine hot after setting zero cold. Not fun, but do it once if you are worried you aren't developing clearance and adjust your cold settings accordingly.
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Jetsetsurfshop
post Aug 24 2018, 12:20 PM
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I found a picture of my camshaft. Its just over a year old.
.006 intake
.008 exhaust
Track car only.
(IMG:style_emoticons/default/driving.gif)
Is this from running lash? The Webcam folks seen it and thought I was at zero lash.
(IMG:style_emoticons/default/confused24.gif)


Attached thumbnail(s)
Attached Image
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euro911
post Aug 24 2018, 12:52 PM
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That could depend on a few factors ...

What did WEB spec for valve lash for that particular cam?
Correct cam break in procedure on initial start up with the correct oil?
What lifters are you running?
What push rods?
What spring tension?
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