If the air tubes to the injectors have never been changed, they may be hard and brittle. Also, if they are old, they may be very difficult to remove without ripping. So you may choose to replace them.

When replacing the valve covers, I find it easier to remove the air tube, then replace the valve cover, and finally replace the air tube. A little silicone lube on the air tube junctions makes for easier removal next time.

One more thought. If you are going to use the old valve cover gasket, be sure to remove all oil from the gasket, including the groove and all oil from the valve cover. By doing this, there will be less probability that the gasket will fall off, when the cover is replaced onto the head, one of those tender moments when you may want to swear if it does fall off.

Those valve cover bolts, 3 NM only!

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1989 420 SEL