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Valve lash 1.6 rocker ratio
https://slantsix.org/forum/viewtopic.php?t=53531		 Page 1 of 1
Author:  Turbo Toad [ Mon Oct 07, 2013 1:41 pm ]
Post subject:  Valve lash 1.6 rocker ratio
I was wondering if it makes any difference in valve lash with some advertised 1.6 rocker arm ratio as opposed to stockers. I'm getting ready to relash my valves and I want to make sure there isn't any difference between the arm ratio.
The only reason for asking I'm seeing some signs of high crank case pressure and I don't remember see anything before I installed the rocker arms at the beginning of the year. So I'm just doing some brain storming and thought I'd ask

Aaron
Author:  Charrlie_S [ Mon Oct 07, 2013 2:49 pm ]
Post subject: 
Crankcase pressure has nothing to do with valve lash, or rocker ratio. In general, crankcase pressure is caused by cylinder pressure, getting past the rings. In theory, and to a lessor extent, some pressure could get by the valve guides, when on boost, and also with the higher back pressure that a turbo can put on the exhaust manifold, but the guides would have to be pretty sloppy.
Author:  Turbo Toad [ Mon Oct 07, 2013 3:36 pm ]
Post subject: 
I do understand that Charlie and thanks response. I'm just tossing things around in my twisted brain.
But I guess my question wasn't answered about lashing the valves with 1.6 rocker arm ratio
Thanks AARON
Author:  CNC-Dude [ Mon Oct 07, 2013 4:58 pm ]
Post subject: 
Valve lash is dependent on the cam grind, not the rocker ratio. It should be set just as the cam card recommends it to be.
Author:  Turbo Toad [ Mon Oct 07, 2013 5:27 pm ]
Post subject: 
For whatever reason I didn't get a cam card from OCG. I'll have to look to see if I still have the copy of the paperwork.
Author:  ceej [ Tue Oct 08, 2013 11:28 am ]
Post subject: 
I've never found a lash value that was worth a hoot on a cam card. Be that OCG, Crane, Comp or whatever.
Generally they tend to be too tight.

If your getting an idle miss, loosen them up a smidge. OCG has lash settings all over the map due to the differences in profiles. What is your grind number? Look in the Engine FAQ, and you should find your cam and lash figures.

Loosen the valve until it makes a loud "tack", measure. Tighten until you experience a miss. Measure. Lash in the middle. Your golden! :D

CJ
Author:  Turbo Toad [ Wed Oct 09, 2013 9:59 am ]
Post subject: 
Ok thanks ceej I guess I never noticed valve lash being on the cam profile page. But sure enuff I found. But I used two profiles 791 was the base and we used a different one for the lobe separation I believe it may of been the 645 but ill have to dig through my notes.

Thanks Aaron
Author:  CNC-Dude [ Wed Oct 09, 2013 10:14 am ]
Post subject: 
If all else fails, just call OCG and get their recommendation.
Author:  Turbo Toad [ Wed Oct 09, 2013 10:22 am ]
Post subject: 
Quote:
If all else fails, just call OCG and get their recommendation.
That's what I might have to do being that it's a duel grind
Aaron
Author:  CNC-Dude [ Wed Oct 09, 2013 10:39 am ]
Post subject: 
Is that all your lacking to get it running?
Author:  Turbo Toad [ Wed Oct 09, 2013 11:18 am ]
Post subject: 
Lord no the car is a beast I'm just getting ready to go through everything and check to make sure nothing has changed. I've made about 13 hard passes under boost from 4psi to 15 psi at the track. But on the last pass the car started acting weird and blue the rear breather out of the valve cover and I'm trying to get to the bottom of this high crank case pressure im seeing, and a member on a different site recommend I check valve lash.
Author:  Turbo Toad [ Wed Oct 09, 2013 11:22 am ]
Post subject: 
One more thing when I installed the rocker arms I installed them with factory lash settings
Author:  CNC-Dude [ Fri Oct 11, 2013 7:38 pm ]
Post subject: 
That will only apply if your using a factory camshaft, all other cams have their own specific lash based on their own unique lobe profile, so you have to have the manufacturers cam card or have spoken with them to know what lash to use.
Author:  slantzilla [ Fri Oct 11, 2013 8:17 pm ]
Post subject: 
Unless you have some wild profile the stock settings were probably real close.

As you've already been informed, lash has nothing to do with crankcase pressure.
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