90 240 DL

89 245 DL

91 740

95 940

ALL non turbos

I need to learn how to do check and replace the valve discs, if necessary, on our several Volvos. I have never done Valves with discs. I understand there is some math that one needs to do. I prefer to do the COLD engine check. I noticed that Volvo lists the millimeters to the hundredths in decimals 0.30 - 0.40 mm, but the inch equivalents to the thousandths(0.012 - 0.016 in.). That strikes me as odd. I am not sure whether to use the metric or inch system when practically applied to checking Volvo valves (murphys law is always there). I have a few questions about doing this task.

First, is it easier or more practical to do the metric decimal or the inch decimal measurement math?

Are the discs marked in both metric and inches?

I have a new Snap-on Go No-Go gauge (labeled Blue Point, # FB-300A) for checking the Valves on our Volvos. This gauge is marked primarily inches, and then millimeters as a second reference. There is no 0.300, 0.310, 0.315, 0.320, 0.325, 0.335, 0.340, 0.350, 0.360, 0.370, 0.380, or 0.390, or 0.400 in millimeters. There is a 0.006" thru 0.012" (.305 mm); and 0.013" (.330 mm); 0.014 (.356 mm); 0.15 (.381 mm); and a .016 (.406 mm) thru 0.030. Evidently the gauge was manufactured primarily for domestic vehicles. In Europe, most of the gauges are strict millimeter gauges. Don't know if any of the European gauges have the secondary markings for inches. The Snap-on dealer for my area says Snap-on does not make a mm's only Go No-Go gauge, or Go No-Go mm/inch gauge. I don't see any in their catalog either.

How critical is having a mm gauge, or a mm first/inch second gauge?

Are the mm's to the hundreds in decimals, without skipping over any consecutive numbers (e.g., 0.30, 0.31, 0.32), better for doing valves than skipping some of the digits? I noticed that most of the blades in mm seem to skip many of the in between mm sizes. Perhaps that is the answer to my question - use whatever you have in every consecutive number. But I would still ask you guys that have done this. No point in jumping to any conclusion.

Thanks, Bruce