Valve Lash (again)

Jeff Frigo · #1 (**permalink**) 07-03-2002, 08:06 PM

How do you guys lash your valves? Can it be done the old fashion by bringing number one piston to TDC, checking the eight valves that are closed, then rotate the engine one turn and check the remaining eight valves that are closed?

Or do you do one cylinder at a time when both valves are closed(must rotate the engine eight times).

I understand the second method is the most accurate, but will the first method work with a big cam? (260 degrees duration @ .050). It is much simpler.

ERA535 · #2 (**permalink**) 07-03-2002, 08:17 PM

I do it one cylinder at a time with the valve on the cam heel.

With a big cam I think this is the only way to fly.

mr0077 · #3 (**permalink**) 07-03-2002, 09:28 PM

Jeff, I'm like ERA535. I've got a milder cam (236 @ 0.050"), but started doing the valves in the firing order sequence (15426378), EXCEPT that when it is up on #1, I do #8 intake and #5 exhaust; move it to #5 TDC and do #1 Intake and #4 exhaust, and continue through the firing order, doing the intake on the previous cylinder and the exhaust on the next cylinder. That way I know I'm on the heel of the lobes and not near the ramp. For example, the intake valve has been closed for an extra 90 (crank) degrees when it is set (and is on the combustion stroke), and the exhaust valve is set while its cylinder is coming up on the compression stroke, 90 (crank) degrees before TDC.
Works fairly well for me.

Mr.Fixit · #4 (**permalink**) 07-08-2002, 05:39 PM

I do it one cylinder at a time, one valve at a time. That way you can make sure that the lifter was on the base circle and the adjustement is correct. Still only takes a couple of minutes.

Hotfingrs · #5 (**permalink**) 07-08-2002, 05:55 PM

I go with the one lifter and one valve at a time...I also go in firing order. Start with #1 cylinder, with the exhaust all the way open, you do the intake, then move to the next in the firing order, and do the same thing. Then you are back at #1. With the intake ALMOST closed, you do the exhaust...this way you know you are on the base of each lobe....You have to turn the engine twice....

Jeff Frigo · #6 (**permalink**) 07-08-2002, 10:08 PM

Thanks guys, that's what I thought.

Andy Dunn · #7 (**permalink**) 07-08-2002, 11:45 PM

here is what Crane suggests

Setting Valve Lash on Mechanical Cams

All the valves must be set individually and only when the lifter is properly located on the base circle of the lobe. At this position the valve is closed and there is no lift taking place. How will you know when the valve you are adjusting is in the proper position with the lifter on the base circle of the cam? This can be accomplished by watching the movement of the valves.

1. When the engine is hot (at operating temperature) remove the valve covers and pick the cylinder you are going to adjust.

2. Hand turn the engine in its normal direction of rotation while watching the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder’s intake valve. (Why? Because when the exhaust is just beginning to open, the intake lifter will be on the base circle of the lobe, so the intake is the one we can now adjust.)

3. Use a feeler gauge, set to the correct valve lash, and place it between the tip of the valve stem and rocker arm. Adjust until you arrive at the proper setting and lock the adjuster in place.

4. After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is almost closed, stop and adjust the exhaust valve on that particular cylinder. (Again, when we see the intake valve almost closed, we are sure that the exhaust lifter is on the base circle of the lobe.) Use the feeler gauge and follow the procedure described before in step 3.

5. Both valves on this cylinder are now adjusted, so move to your next cylinder and follow the same procedure again. In the future you may find shortcuts to this method, but it still remains the best way to do the job correctly.

hope this helps

Andy

xlr8or · #8 (**permalink**) 07-09-2002, 12:10 AM

Andy you are completely correct. I had just recently read an article about adjusting the valve and that exact process was detailed and holds true for any 4 stroke engine no matter how many cylinders.
Used that method two weeks ago on my truck and it worked great. It's much easier that way to keep track of whats been adjusted and whats not.

Now if we can just settle that hot/cold adjustment difference.

Scott

ERA535 · #9 (**permalink**) 07-09-2002, 12:24 AM

Scott-

You can settle that yourself.

Adjust the valves to spec hot, then let it cool down and check what they are.

You only have to do one.

It is not very complicated!

Jeff Frigo · #10 (**permalink**) 07-09-2002, 01:33 AM

Andy:

Sounds almost good to me, but how much is "almost" closed? How does this sound to everybody: Mark your harmonic balancer every 90 degrees (you can buy adhesive tape that is specially marked for harmonic balancers). This way you can tell when any given piston is at TDC. Adjust both intake and exhast one cylinder at a time with each one at TDC on the compression stroke (both valves closed).

Hotfingrs · #11 (**permalink**) 07-09-2002, 06:12 AM

Jeff that might work, but when you're running a big number cam and have it advanced x number of degrees, it makes it hard to find tdc. This spring when I changed valve springs using compressed air to hold the valves up, I could barely find tdc, there was such a fine line between one of the valves being open and both closed, that on every cylinder I had to rock the engine back and forth to find that spot. I've used the system that I describe in a post above, and also posted by Andy, for years with great success......

Jeff Frigo · #12 (**permalink**) 07-09-2002, 06:32 AM

Hotfingrs:

But what is almost closed? Does not sound very scientific. I wold like to do it to an exact "spot" every time. BTW I just replaced a couple of valve seals using compressed air like you said. I had the car in gear without the e-brake on and boy did I get a suprise when the car rolled forward about a foot because the air pushed the piston to the bottom of the stroke. Thank God it went forward, I had the rear end right against the door.

Hotfingrs · #13 (**permalink**) 07-09-2002, 07:02 AM

I use about 3/4 of the way or a little more closed, using the intake spring as a guide to know when you are close to being there. Actually there is quite a bit of room there to play with...

Jeff Frigo · #14 (**permalink**) 07-09-2002, 07:21 AM

I gotcha. I'm sure as soon as I do it that way, I will say, "Da".

Mr.Fixit · #15 (**permalink**) 07-09-2002, 09:33 AM

E.O.I.C as the Exhaust open (do the intake)
as the Intake closes (do the exhaust)