1. Set the valves cold – let it sit overnight. If hot or warm the metal will have expanded, and the gap smaller than when cold. If you set the valves warm/hot, when the engine cools off the gap will be larger and the adjustment too loose.
2. Take records of the following as you go:
- Plug color and gap per plug – to monitor over time the mixture per cylinder
- Pre-adjustment valve clearance per cylinder per valve – if the clearance on a valve keeps getting tighter each time you check it, you may have a valve seat getting pounded down. This is a great way to monitor a head that has not been rebuilt for unleaded gas. Erratic readings, going tighter and looser, may indicate rocker arm or tappet wear.
- Post-Adjustment valve clearance per cylinder per valve (see the “T” and “L” notes below).
3. Wipe around Valve Cover with a rag, remove the Valve Cover with a 1/2 deep socket and speed wrench. I do this before removing plugs just to prevent any junk from falling into plug holes.
4. Remove the spark plug wires from the plug side only, being careful to pull them from the boot rather than the wire so as to not pull the wire off from the connector. Leave them in line with the plug you removed. Remove all the spark plugs with the speed wrench + extension, recording the color (sooty, brown, white) and gap, to make it easy to turn the engine
5. The “Rule of 13” is a slick way to know which valve to adjust on a 6 cylinder engine. If 1 and 3 are open, 1 + 12 = 13 and 3 + 10 = 13. Thus 12 and 10 are the valves to adjust. Look at valves to see which pair seems to be open from the chart below. A valve is open when the adjuster side of the rocker is up high, and the spring side is down low. (Note: someone pointed out that the order of the chart is inverted. Work your way UP the chart not down. I will verify this next time I set my valves)
|Rule of Thirteen – Valve Adjustment Order|
|Open Valves||Check and Adjust|
6. Choose the NEXT pair of valves that will open from the chart (a reader tells me the chart is inverted, so NEXT is UP if they are right. I will check next time I set valves), and put your fingers from your right hand on the adjusters. I choose the NEXT pair in case the pair that appears open is already starting to close. Your sense of touch is very sensitive, and you don’t need to watch the valves, you can easily feel when both adjusters rise, and when the one starts to descend. The reason I choose the next pair is so you can be sure they are fully open and am not tempted to turn the engine backwards, which you should never do. You want to keep the timing chain tight in the direction of the normal rotation of the engine.
7. With your right hand fingers on the adjusters, take your left hand, reach down and pull the fan towards you, turning the engine clockwise. If you have the right pair of valves, they will both start to open after only 30 degrees of rotation (a couple blades worth of rotation). If only one valve opens, you have the wrong pair, Keep turning the engine clockwise only just a little bit until one of the valves just barely starts to close (when the adjuster side starts to go back down). DO NOT turn the engine backwards if you go too far. Just go on to the next pair, and adjust the ones you missed on the next full rotation..
8. Record the valve clearance of the fully closed pair that pairs with the fully open pair on the chart. So you are not recording the valves you have your fingers on, but the matching pair from the chart. Use the go/no go method with .008, .010, and .012 feeler gauges. The largest one that will “go” is the one you record. I will put a “T” if it is a little tight, an “L” next to the value if a little loose.
9. Put a screwdriver that fits snugly in the adjuster, and loosen the nut by about a “flat” with a 1/2 end wrench on the adjuster, keeping the slot from turning with the screwdriver as best you can. Tighten or loosen the adjuster as appropriate by about a half of a flat of a nut, and tighten the nut, again holding the screwdriver firmly to keep the adjuster from turning along with the nut. This takes a little practice, and you may need to eyeball it a little if things get away from you. The important thing is to watch the adjuster slot, and have it end up a little clockwise or counter clockwise as is appropriate when you are done tightening the nut. Verify the adjustment with a go/no go test, setting both intake and exhaust to .010. Record the result for each valve. If it is a little loose on the .010, but the .012 won’t go, I record this as .010 “L” and move on. A tiny bit loose is ok, but you don’t want it too tight – “T”. By recording it as .010 “L”, you can judge if the seat may be wearing if it is .010 “T” next time, or consistently each time you compare.
10. Put a dollop of Vaseline on each adjuster as you go to keep track of the fact you adjusted it. (Optional, but helps me keep track).
11. Repeat for each pair of valves until you are done. If you miss a pair, just keep going and do an extra rotation to catch the one/ones you missed. The “law of 13” method doesn’t require full rotations, and the spark plugs being out makes it easy to turn, so it won’t take you much to get back to that pair of valves.
12. Double check: go through the process again, double checking all the valve settings. This doesn’t take long. If you have any that fail this test, you need to ask yourself if your valve rocker arms or tappets are worn. Set the offending valve again, and go through another rotation to see if it still fails.
13. Put the plugs back, putting a little Anti-Seize on the threads first. Nothing is worse than stripping a spark plug hole, or breaking off a plug, and the anti-seize will make them come out easily next time. I put them back in the same cylinders so I can track the mixture in that cylinder by the color consistently. Use the Speed Wrench plus extension, and tighten to the equivalent of hand tight, and then a slight extra turn, maybe two “hours” or so of a clock face. Like from 1 O’clock to 3 O’clock.
14. Put the wires back on, verifying the firing order as you go. (No.1 at front) 1,5,3,6,2,4 going counterclockwise. The wires should be close to the correct plug holes anyway, so just make sure you didn’t get them crossed over.
15. Put the Valve Cover back on, don’t over tighten it. I use the same rule of thumb as for the spark plugs, tighten till snug, then a little more, about 2 numbers on the clock face. (Replace the gasket first if it was leaking). Be sure to put the emissions hose back.