Valve lash

[emptyhead]

Finally pulled off the valve cover on the side I'm having problems with and a question or two. When measuring the lash in the valves do you do it on tdc. When I have 4,5 and 6 at tdc I have no gap at all between the lifters and valves. Can't even get a 005 feeler in between. Thanks

[autocar925]

There are two TDCs, the firing TDC and the end of exhaust TDC.  You may be on the exhaust TDC so you need to spin the crankshaft one whole revolution to end up at the firing TDC to check the lash.

[emptyhead]

I was checking with the distributor when the points open on each of those cylinders but will check again. Thanks

[autocar925]

If the spark wires are installed in the correct order, it looks like you would be checking the lash on the correct TDC.  This engine has been running fine and then a problem popped up or you are just getting it going?  If just getting it going for the first time, I would look closely at the firing order and plug wiring.  If previously running fine, then probably something like burned/worn valve faces and they are sinking into the block taking away all the valve lash.

[emptyhead]

Was running rough didn't fire it up till a year and half from picking up from builder. Checked 1,2 and three not much if any lash in those either.

[HenryVIII]

Hi
 It sounds like you have the exact problem I had when I got my engine back from the builder. I was looking in my tech manual for the engine about checking the clearance for the valves. TM9-1711 page 214 and it only has one sentence about checking valve lash.  I will quote it for you.

 "Rotate the crankshaft and when each valve is in its closed position, hold valve lifter for closed valve down and check clearance between valve lifter and bottom of valve stem (.040-in.-.080-in.).

If you rotate the engine until the lobe on the cam is pointing down you can set the valve lash. as long as the lobe is not lifting the valve you will be good. It should not matter what the firing position. You will want the clearance measurement with the lifter collapsed or compressed. you will probably have to remove each valve and grind the end of the shaft to shorten it to the correct clearance. another way... the way I did it.... was to machine the lifter cup top edge to shorten the lifter. this will get you the same result and you will not have to remove the head. But I do NOT recommend this because the lifter will now be shorter and you cannot put the metal back on and the lifters will be too short if you replace the valves or seats.  Shorten the valves...they are cheaper and easier to replace and it is the correct way to do it.

Best of luck.  Henry     

[emptyhead]

Ok so I have to hold the tip of the tappet down to move it away from the tip of the valve stem.i thought the lifters would bleed down. Thanks . I'm a little dense sometimes

[HenryVIII]

The lifters will probably not bleed down unless there is pressure on them or unless they are really worn.  I used a small flat screwdriver to insert between the stem and lifter. Just be careful not to scratch anything. It does not take too much pressure, and you do not want to lift the valve. There is a small spring on the lifter, its not very strong. it takes up the slack so the lifter can fill with oil. the oil will prevent the spring from compressing when it is running. the cushion of oil is what allows the lifters to constantly adjust as the valves expand or wear.     

[HenryVIII]

If the feeler gauge does not work or you cannot get the lifters to drain down you may need to go to the next step.

I did some more looking about the valves and have some more info. one of the things that might work to check if the valves are ok is to make a go-no-go gauge. the measurement of the lifter when compressed is 3.550 inches and 3.700 inches when not compressed. The book says you have to remove the lifter and use a small wire to push the check ball in to let the oil out.

To let the oil out you have to remove the lifter assembly from the engine. Then remove the one lifter from the guide block. Do one at a time and don't mix parts. The lifter will come apart into 3 sections 1. a larger bottom section 2. a middle section with a small tube on one end and 3. the upper section with the small spring. reassemble the middle and upper sections. While pushing on the spring with your finger insert a paperclip or small wire into the small tube, this will unseat the check ball and let the oil out. Be careful not to squirt yourself in the eye. The little springy piston should have a range of .150 thousandths. check the spring. If the check ball did not hold or oil psi was too low at some, the spring could be damaged or broken.

The lifter body will also be easier to get back in if the lifters are collapsed. It can be done without propping the valves open. Its a pain but it will go, I did it several times.     
 
If you remove the lifters you can use the gauge to see if the valves are sitting too low from grinding. If you make a go-no-go gauge that is 3.590 and 3.630. aluminum or plastic works best, Place it between the camshaft and the end of the valve stem, if 3.590 will not fit you are below the minimum spec for the valve lash, if 3.630 will fit you are over the spec. Be sure to have the cam lobe pointing down when you do this measurement.

You should only have 5 psi difference from the highest to lowest cylinder pressure. I can try to post some pictures if my description is confusing. I am curious to know what you find.

Good luck   Henry     

[emptyhead]

Thanks Henry I did another compression test and all where within 5 psi of 120. Thanks for the write up on the valve check. If I can't get the engine builder up here then I think it's the next step. I'll try to do it with out taking off the head and see where I wind up. Thanks

[yd328]

I don't think I am that far from you, if you need a hand I can drive over.

Gary