A: From Bruce Godfrey (godfrey@admin.ogi.edu)

You _always_ have to keep the valves adjusted, no matter what cam you have in there! When the valve is closed and the cam lobe is pointing up away from the rocker there should be a clearance between the lash pad surface and the rocker arm tip as specified in the Haynes manual (for instance) for a stock motor or as specified for the particular cam for a modified motor. If there is _no_ clearance, then the valve is never being allowed to close all the way and hot exhaust gasses are flowing by it all the time. Two bad things happen then, the valve head gets really hot from those exhaust gasses going by all the time, and it never has a chance to pass any of that heat to the coolant via contact with it's seat.

This results in the valve getting WAY TOO HOT and it burns just like if you had attacked it with a cutting torch. It happens very quickly to exhaust valves with no clearance, intake valves are cooled once a cycle by the cold air/fuel mixture being inducted by them on the intake stroke, so they can stand this abuse longer.

Fix the situation now, or suffer the consequences. It only costs about $15.0-20.00 to pay a mechanic to adjust the valves this one time (lowest price in Tucson is $56 - Kendel), and then you can learn to do it at your leisure in the next year. Don't wait longer than that though. Do it at least once a year and check them at every tune up.

A: From Rex Jennett (jennett@svpal.org)

Lack of valve clearance will also cause another problem: it will make your car hard to start (or it won't start) when the engine's cold, due to low compression. I've learned this the HARD way, when everything else seemed to be all right. The original factory book says to check clearances every 6000 miles, but it's amazing how many NEVER check this. I think that every 6000 is overkill, but every 12000 is a good idea if you want to keep performance up.

Q: Now that I know about my valve sins, how should I adjust them?

A: From Thomas Walter (walter@roadster.sps.mot.com)

HOW TO ADJUST YOUR VALVES:

Adjusting lash pad clearance:

{I'll talk you through doing this on a COLD engine, hot is recommended... but for the first time you are doing this you'll take much longer than normal, letting the engine cool down too much between adjustments... plus burning your fingers}

Label a piece of paper like so:

E I I E E I I E

Car in neutral, ignition OFF, remove the spark plug wires, and loop back over the air cleaner (to keep them out of the way).

Remove the valve cover (6 bolts). First time it has been off in a long time, it might be stuck. A tap with a RAWHIDE or RUBBER mallet will loosen it. Leave that ball-peen hammer in the tool box. Trust me on this one. :-)

Slip the small wire off the starter. An old screw driver can be used to short from the big battery cable to the small male terminal. Short the two together, and the starter will crank - rotating the camshaft.

Point the "tip" of the first lobe towards the sky. The rocker is against the heel of the cam. Slip a feeler gauge between the camshaft and rocker. It should just slide between the two. Try a 0.003" one... should slip right on through. Try one labeled 0.020" it should not be able to pass through the space. Once you've worked at getting the feel correct, you should be able to slide one at 0.011" through, but the one at 0.013" should not be able to pass. At 0.012" it should have a slight drag, but that will confirm the setting.

If you measure only 0.004" clearance, then you need to adjust the valve. Use a 17mm open end to loosen the lock nut, 14mm to adjust the pivot. Starting out, measure the clearance once loose. Move the pivot 1/8 of a turn, and notice how much the clearance changed. Takes a little bit, but you'll get the hang of it.

Once you think you have it adjust just right, you'll use the 17mm wrench to lock down the setting... opps, the clearance just changed! Even holding it with the 14mm wrench, the tightening the 17mm will cause it to LOOSEN slightly (about 0.001 or so). I just plan ahead, and adjust slightly loose (let the 0.012" just slide through) then tighten in down again, and check again.

Usually once I have done that valve, it is time to move on to the next. Hence my paper note (written on scrap newspaper, with a big felt pen): I'll put a big X through the one I just adjusted, tap the starter and do the next valve that is ready to go! Don't worry about any order, the paper keeps track of what was done. I'll also make a note on how loose, or how tight, the setting was. (I keep these notes to track if a valve suddenly keeps changing lash... something is wrong if it does!)

When the intake valves get pounded into the head, literally the valve is sinking, the clearance is less and less. My '71 Wagon had 300,000 miles on the motor... head had NOT been removed! The #4 intake was sitting with 0.006" clearance, as there was no adjustment left. Admitted I could have removed the lock down nut, and used a thinner one, but every time I checked the clearance remained constant. When I sold the car I told the new owner about it, and gave him a spare rebuilt head I had gotten... just waiting for the rainy day to install it!

COLD ADJUSTMENT:  Intakes: 0.008"
                  Exhaust: 0.010"

HOT ADJUSTMENT:   Intakes: 0.010"
                  Exhaust: 0.012"

Usually my adjustments are done cold. I'll inspect the clearance HOT, to make sure nothing was missed... but there seems to be a 5 minute window (at the most) to check... plenty of time!

P.S. I like Yogi's idea of the "go, no-go" feeler gauges. Being cheap I'll stick to my "leave three out, the rest in" way. :-)

NISSAN TECH TIP: for hard starting L28 engines, NISSAN had recommended increasing the intake valve clearance +0.002" to 0.010 COLD and 0.012" HOT. (Factory bullentin around 1976?)

HANDY TIP:

Read of a fellow keeping all his vehicles tune up/oil change/etc data on a 3" x 5" card. stuff like:

Sunbeam Tiger:
Plugs: XYV gap 0.032"
Oil drain plug 7/8"			
Filter:  abc123             (4.5qts w/flt 20W50)
rear end plug: 1/2" male	(90w)
transmission: 7/8" square   (90W)

I keep an old Haynes manual in the garage, with notes in it.... with a couple of torque values having a line through them and the correct values noted (cam bolt, and cam tower bolts had WRONG values in the original printing!). Handy to flip through and jog the grey cells before doing something (like valve adjust!).