Setting Valve Lash, Different Everytime?? - Team Camaro Tech
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post #1 of 12 (permalink) Old Jun 4th, 19, 10:36 AM Thread Starter
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Setting Valve Lash, Different Everytime??

Hello, I am in the process of checking the valve lash, and each time I recheck, I get a different reading. I am using the EO/IC method, starting with the intake valve on number 1 cylinder and working my way through the firing order.

I have poly locks on the rockers, I can't tell if it's the poly locks or if there is something else going on the in the valve train that I am not seeing? The lash seems to get tighter. Could it be as simple as me misreading when the valve is on the base circle? Any suggestions?

When the exhaust just starts to open, I adjust the intake.

When the intake opens all the way, then half way closed, I adjust the exhaust.

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post #2 of 12 (permalink) Old Jun 4th, 19, 10:52 AM
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Re: Setting Valve Lash, Different Everytime??

Sounds like you are doing it correctly. Is this a new engine ?

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post #3 of 12 (permalink) Old Jun 4th, 19, 11:41 AM
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Re: Setting Valve Lash, Different Everytime??

I don't do it when the valve is just starting to open but at wide open. If you have enough over lap you will never be on the base circle.

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post #4 of 12 (permalink) Old Jun 4th, 19, 12:03 PM Thread Starter
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Re: Setting Valve Lash, Different Everytime??

@BillK, no it's not a new engine, unknown milage and I have owned the car for about 10 years. Could I end up wiping a cam lobe if the lash it to out of adjustment?

@dave, can you clarify, are you talking about the exhaust valve?
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post #5 of 12 (permalink) Old Jun 4th, 19, 02:23 PM
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Re: Setting Valve Lash, Different Everytime??

If the exhaust valve is at full open you adjust the associated cylinder's intake valve because it is now at base circle. By the way another consideration is the temperature of the motor. It has to be hot! Aluminum heads can expand by 0.004", taking that off the lash result in them being too tight.

I like my valves tight because it results in more lift. I love lift and do everything in my power to promote lift and reduce duration, if I can to obtain it.

So can you wipe a lobe by having your valves out of proper lash. No! Not unless they are so loose that a push rod jumps out and roller lifter breaks a bar turning in the bore to destroy the cam and lifter (and push rod, that plus the miscellaneous parts falling through your engine). You wipe a cam by not providing enough lubrication between parts that are metal on metal. In a metal on metal situation you want a sacrificial metal to be consumed, not the face of your cam. That is where high Zinc and Phosphorous come into play. They get between the steel lifter and the cast iron cam lobe and are destroyed by the friction produced at the point of contact.

Problem is the same person that worries about being hit by an asteroid, worries your high dollar hot rod motor might become an oil burning clapped out engine in the distant future. Such a clunker Might MayBe allow some of that burnt oil to get past a log cast iron manifold where the heat from a working cylinder would complete the combustion before it got to the cat. They are worried about fouling the three way catalytic converter that you do not have (unless you are driving a fifth or sixth gen Camaro). The tree way cat converts CO to CO2 rips O2 free from the Nitrates in your exhaust (caused by having a high compression motor) and takes that free oxygen to bun the hydrocarbons in your exhaust to release only water and CO2 (along with some flowers and puppies). The fact that most of the Camaros on this board don't have even a basic (1975) style cat that could eat burnt oil for breakfast isn't even considered in their thinking. Gotta be safe, Save the planet and ban classic cars.

So there is very little (read not enough) Zinc dialkyldithiophosphates (often referred to as ZDDP) in your motor oil to run a flat tappet cam. That will wipe a lobe.

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post #6 of 12 (permalink) Old Jun 4th, 19, 02:40 PM
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Re: Setting Valve Lash, Different Everytime??

E - exhaust
I - intake

E-O, when the exhaust lifter just begins to move just off fully closed
I-C, when the intake valve just comes completely closed

These are the points the lifter face is at the center of the cam lobe being adjusted's dead center point, not up on a ramp, not here or there, but dead center on the base circle of the lobe.

Now, if anyone wants to challenge (which has been done numerous times, with the SAME results, please go head on with it), because, after all, all I am is a moron about engines, all I do is ignition systems and RACE ENGINE DESIGN for MotoGP. We will need someone with a block and cam bearings, cam for that engine, any will do, and two lifters. Insert cam and lifters into block, identify ONE set of valves, one exh, one int, and turn the cam until the E-O, I-C points are reached, and look at the lifter and lobe through the crankshaft cavity, report back.

Works on EVERY cam, and EVERY grind ever made, has since Egyptians built the Sphynx using a /59 Chevy 4 door station wagon.

Not here, there, in between, or over there, next week, the year 2030, standing on one's head, just what it says above.

To use Poly-Loc's correctly, the top of the stud needs to be ground squared off, no divots, no cups, and, it takes a bit of practice to et the things adjusted correctly. The stop screw will raise the Loc up the distance of the thread to thread clearance as it is tightened, if done that way, and, some get the hang of tightening both the stop screw and Loc together to set the Loc.
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post #7 of 12 (permalink) Old Jun 4th, 19, 03:36 PM
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Re: Setting Valve Lash, Different Everytime??

Hydraulic lifters ?

If so, sounds like they're collapsing some as you rotate the motor over.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #8 of 12 (permalink) Old Jun 4th, 19, 05:46 PM
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Re: Setting Valve Lash, Different Everytime??

Quote:
Hydraulic lifters ?

If so, sounds like they're collapsing some as you rotate the motor over.
If Hydraulic why not just preload a quarter turn to half turn and be done with it.

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post #9 of 12 (permalink) Old Jun 4th, 19, 07:03 PM
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Re: Setting Valve Lash, Different Everytime??

Hydraulic lifters need to be set in the same pla ce a solid, roller need to e, E-O, I-C still in play.

Yes, without oil pressure to the lifter, as in a NON-RUNNING engine, hydraulic lifters will collapse somewhat when the engine is turned over, but, if you do this when you build the engine, with the manifold off the engine, you can see the push rod push the lifter button down when all clearance is eliminated, THEN, add the 1/4, 1/2 1 full turn you desire.

Even with the manifold on the engine, you just have to set the valves with the E-O, I-C method, and learn to feel the rocker/push rod to tell when every lifter gets to no clearance, no preload, and adjust from there.

It still isn't that hard to get it right, the very first time.
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post #10 of 12 (permalink) Old Jun 5th, 19, 11:28 AM Thread Starter
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Re: Setting Valve Lash, Different Everytime??

It's a solid lifter, thanks for the replies, I will go back and try again but with a little more patience while paying close attention to the rockers as they move. I am just turning the engine over by hand, 1/2 ratchet on the lower pulley and all the spark plugs out. I always do it cold and add +0.002 to the setting, heads are iron.
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post #11 of 12 (permalink) Old Jun 5th, 19, 02:14 PM
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Re: Setting Valve Lash, Different Everytime??

Solids, shouldn't move once set, so I understand your issue with them now.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #12 of 12 (permalink) Old Jun 5th, 19, 03:33 PM
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Re: Setting Valve Lash, Different Everytime??

OP

How much of a variance are you getting .00x? or .01x?

and what is the gap measurement? (if zero than that can be a problem)

is this variance in measurement after motor has been run or still cold and you are just rotating engine by hand and checking gap again.

If the former you might want to add .003-.004 and see what you get after a few heat cycles

If the later it may have more to do with your EO/IC RR position if "eyeballing" the RR. With that said you can't be very far off from the 6 o'clock position of the base circle (read 5-7 referencing clock position)

I can add a note about "can you wipe a lobe if valve adjustment is not right". Yes. Solid or short travel hydraulic (racing) lifters with the later requiring 0 to 1/8th turn max of pre-load past ZERO lash (often this is were people FU on hydraulic lash) you can wipe a lobe (talking from personal experience) if lash is to tight. Typically the valve won't close all the way and motor will run rough so you can catch a to tight lash before any damage is done. Un attended...it can and will wipe a lobe

As noted there are certainly other ways to wipe a lobe and using a high zinc content oil, especially with SR cam/lifters, is a good idea IMHO.
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