VCI logo Archive Index | Current Issue
Valve Adjustment
Phil Singher

The first step of any engine tuning is to ensure that valve adjustment is correct. For B18 and B20 motors, Volvo recommends checking this at 6,000-mile intervals. I make a habit of checking this twice as often (whenever I do an oil change), although adjustment is rarely needed once a new motor settles in. It's a good diagnostic tool -- if valve clearances tighten up, it's a pretty sure sign of valve seat erosion; a matter of some concern with today's unleaded fuels.

Incorrect valve adjustment is not only detrimental to performance and engine longevity, it can also fool one into thinking more serious problems exist. We recently compression-checked a motor that couldn't be made to idle smoothly with any amount of tuning and obtained readings that varied greatly from cylinder to cylinder; normally an indication that a rebuild was imminent. This turned out to be nothing more than poorly set valves, much to the owner's relief.

As an experiment on one of my motors, I tightened valve clearances just .002" under the "usual" setting and found that this had a profound effect on the way the carb needed to be jetted. Camshafts are engineered with particular clearances in mind -- these are factored into the design of the cam profile. When one varies from the recommended clearance settings, one is effectively altering the way a cam was designed to operate. I don't mean that as a "thou shall not;" just reinforcing my point that valve settings have a global effect on engine tuning.

The Haynes manual method for setting valves -- setting #1 when #8 is fully depressed, #2 with #7 down, etc. -- has worked pretty well for us until recently. Here's a method I find I like better, though, that works with any cam profile -- courtesy of David Hueppchen, who got it from Waddell Wilson years ago:

  1. Bring the motor up to full operating temperature (this means, of course, that you want to adjust the valves to the "warm" spec found in your manual or supplied by an aftermarket cam's manufacturer).
  2. Remove the spark plugs so the motor's easier to turn (I turn it with an adjustable wrench on the crankshaft pulley. Also -- needless to say, I hope -- make absolutely sure you know which plug wire goes back on where).
  3. Turn the motor in the direction it normally runs -- clockwise, looking at it from the front of the car -- until an exhaust valve just starts to open. Look at the manifolds to see which are exhaust and which are intake valves. OK, I'll make it easy: counting from front to back, valves 1, 4, 5 and 8 are exhaust valves.
  4. At this point, adjust the intake valve on that cylinder. In other words, when the rocker arm on exhaust valve #4 just starts to tip downwards, adjust intake valve #3.
  5. Keep turning the motor through two complete rotations and adjust all the intake valves in a similar way.
  6. Go around two more times, adjusting each exhaust valve just as the intake on the same cylinder begins to close. In other words, when the rocker arm on intake valve #3 just starts to come back up from being fully depressed, adjust exhaust valve #4.

Once the valve adjustment is correct -- and only then -- you're ready to set ignition timing and tune carburetors.

I like David's method a lot better than the way I've been doing it all these years -- and I'm sure you will, too.

Back to the Top