valve lash adjustment

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Frank Enstein

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This is something I wrote up for work.


Here is the procedure to adjust the valves on a new 8 cylinder engine:

Turn the crank clockwise while watching the number one cylinder pushrods.

Watch the exhaust pushrod go up and down and then the intake pushrod go up and down.

Continue to rotate the crank after the intake pushrod goes all the way down until the timing marks

Line up on 0 degrees.

(This will be LESS than 1/2 turn of the crank after the intake pushrod is all the way down.)

Install rockers and tighten the nut while rattling the pushrods up and down until the rattle just stops.

At this point you are at ZERO LASH.

Tighten further to add your preload ( typically 1/2 turn after the rattle stops ).

Do this to both rockers for number 1 cylinder. Cylinder number 1 is DONE!

Now turn the crank 90 degrees ( 1/4 turn) and set the rockers for the next cylinder in the firing order.

After the second cylinder in the firing order turn the crank 90 degrees and set the third cylinder in the firing order.

Repeat this procedure for the remaining cylinders, one for each 90 degrees of crank rotation

ending with the last cylinder in the firing order.


After the last cylinder in the firing order's rockers are set turn the crank until the timing marks

line up with 10 degrees BEFORE top dead center (BTDC).


Install the distributor aligning the rotor with the cap location that you want to put number 1 spark plug wire.

Line up the magnetic pickup with the reluctor and then rotate the distributor opposite the direction of rotation

JUST SLIGHTLY until the points are BARELY misaligned. Tighten down the distributor.

You are now pre-timed for 10 degrees Before TDC. And the engine should start right up!
 

eran tomer

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Line up the magnetic pickup with the reluctor and then rotate the distributor opposite the direction of rotation

JUST SLIGHTLY until the points are BARELY misaligned. Tighten down the distributor.
why do you have to misalign it again after you aligned it?
 
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Schurkey

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Not contact points for a "points" ignition that requires setting dwell/gap. He's talking about the lil' triangle points on the reluctor and pickup coil of an HEI ignition. Downside is that while they're easily visible on earlier units, the TBI distributors have them shielded with a sheetmetal cover so that they're near-invisible. And, of course, there's no reluctor/pickup coil in a Vortec distributor for timing of the ignition.

TBI
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Older HEI
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Schurkey

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why do you have to misalign it again after you aligned it?
I don't deliberately misalign them. I install the distributor with 'em aligned. This can be done almost by "feel", as there's a weak magnetic attraction between the inner and outer teeth.

Gets the initial timing close enough to reliably start the engine. Adjust as needed to achieve perfection once the engine runs.
 

Frank Enstein

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why do you have to misalign it again after you aligned it?
Because that's when it fires the coil. As the points get closer together the voltage goes up and is at it's peak when the points are aligned. when they go past the closest alignment and start to get farther away the voltage drops. That is when the module cuts the ground to the coil causing it to fire the spark.
 

AK 99

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The valve covers are off. You're looking at the valves/valve springs, and you're looking at the intake and exhaust manifolds.

Which valves line up with the intake runners? Those are the intake valves.
Which valves line up with the exhaust runners? Those are the exhaust valves.

But if you do it my way, listed in Post 15, IT DOESN'T MATTER which valves are intakes and which are exhausts. You don't need to keep track, and you don't need a piece of wood with writing on it. There is no more-simple way to do it.

I may be an idiot, but I do not understand exactly what you were saying in post #15.

If you are saying that the engine does not need to be TDC or 180 out from TDC, how the heck does that work? Lash needs set on the base circle of the lobe.

If you are saying to start at TDC or 180 out from TDC, that's the same basic method that I posted. The only difference is an added step of tightening half of the valves twice, for those that don't know which valves are which.
 

Schurkey

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If you are saying that the engine does not need to be TDC or 180 out from TDC, how the heck does that work? Lash needs set on the base circle of the lobe.
Of course they have to be set on the base circle of the lobe. The base circle of the lobe is more than 1/2 of the lobe, how much more depends on the duration of the cam lobe.


If you are saying to start at TDC or 180 out from TDC, that's the same basic method that I posted. The only difference is an added step of tightening half of the valves twice, for those that don't know which valves are which.
You posted a method that requires adjusting specific valves at certain times, and the crank has to be in a specific position for each step. A guy has to know which cylinder he's working on, and how to tell an intake valve from an exhaust valve.

With the method I suggested, you don't need to pay any attention to which valves you're setting. It DOESN'T MATTER if they're intake or exhaust valves, and it DOESN'T MATTER which cylinder you're working on. There's essentially nothing to keep track of beyond working from one end of the engine to the other without missing any valves, and being able to assess "loose" or "tight". Therefore little chance of screwing-up provided you can reliably find "zero lash"; and you can pick a preload amount that suits your lifters. (But if you can't find "zero lash", and if you can't pick a preload amount that suits your lifters, you will not be successful with any other method; EVERY method, no matter how much more complex that this, requires those two things.)

My method is very similar to yours, but with simplification. As a bonus, my method would work for engines with different cylinder numbering, different firing orders, or even different cylinder counts--V12, V6, inline 5, etc. For the record, I learned this method from a guy with the user-name "Motor Daddy" on another forum.

Loosen 'em all, if they aren't loose already.
Tighten 'em all to zero-lash.
(Because more than half of each cam lobe is base circle, more than half of the lifters will be on the base circle of their lobe no matter where the crank is positioned. The others will be lifted by the cam lobe, but we'll correct those later.)
Turn the crank one revolution from wherever it was. It DOESN'T MATTER where the crank was positioned initially. Just turn it exactly one turn--360 degrees. Because more than half the cam lobe is base circle, any lifter that wasn't on the base circle before, is on the base circle now. Those rockers will now be loose.
Tighten only the loose valves to zero lash (fewer than half will be loose. If they're tight, leave 'em alone.) In two rounds of tightening, with one turn of the crank, EVERY LIFTER IS NOW ADJUSTED TO ZERO-LASH ON THE BASE CIRCLE OF IT'S CAM LOBE. (But they're not all on the base circle any more. Some are...some aren't. DOESN'T MATTER.)
Tighten 'em all to whatever lifter preload floats your boat--1 turn, 1/2 turn, 3/16 turn, 1/64 turn--anything that will work with your lifters.
Put the valve covers back on.

It does not get any more simple (or universal) than that.
 
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AK 99

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You posted a method that requires adjusting specific valves at certain times, and the crank has to be in a specific position for each step. A guy has to know which cylinder he's working on, and how to tell an intake valve from an exhaust valve.

It's the same method. Adjust half the valves at TDC, adjust the other half at 180* from TDC. The way you describe it makes it more idiot-proof, I get it. But it's the same basic method. Only difference with your method, if you don't know which valves are which, you have to adjust half of the valves twice. With my method, (it's pretty darn simple to know which valve does what), then you only have to adjust each valve once.
 
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