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Old 09-06-2001, 11:04 PM
Coming back from burnout
Join Date: Jun 1999
Location: in the Pacific Northwest
Posts: 2,274
Help. Setting Valve Clearances always did confuse me....

The 1985 300D Service CD tells you to set the Exhaust valve clearances to .35 mm and your Intake valve clearances to .10 mm. It also tells you to set the clearances when the Cam shaft/Rocker Arm relationship is as shown in the bottom right of the Diagram.
Which of my following reasoning/logic/assumptions is wrong?Something really confused me this afternoon.
(1) When the Camshaft and Rocker arm are as positioned in the Diagram, the valve is fully closed. That is because at this position the Camshaft places the least pressure on the Exhaust valve and allows the Spring to expand, closing the valve fully.
(2) Therefore you can use the Table to set the camshaft very accurately. For the top engine listed, for instance, when you are at 19 degrees before Top Dead Center, the Exhaust Valve should be fully shut and the Rocker/cam relationship should be as in the figure below.
(3) You must set the valves sequentially from front to back as you spin the crank clockwise and you must do this in a precise sequence of Crankshaft spinning.. If you over spin the crank and pass TDC by accident, and you are on the Fourth Intake valve, you must start all over from Valve One. You are not allowed to rotate one more revolution to get back to 13.5 degrees BTDC.

My assumptions are (1) Just go by the Diagram
(2) You will never get the rocker arm/camshaft relationship shown in Diagram (assuming it shows Valve fully shut) by using this table. Please disregard the Table.
(3) You can skip TDC as many time as you want. You can even jump from valve 1 to Valve 3 to Valve 5 back to valve 2 when you work on them, it makes no difference as long as if you have the Diagram's rocker/cam relationship.
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Old 09-06-2001, 11:13 PM
Senior Member
Join Date: Apr 2001
Location: Beech Island, S.C.
Posts: 468
You're trying to make an easy job hard. Turn the engine using a 22MM wrench on the power steering pump and when the cam lobs point at 1 o'clock looking at if from the front of the engine just figure out if it's the intake or exhaust valve and adjust it. It's easy to tell which valve it is buy aligning it with the exhaust or intake manifold.
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Old 09-07-2001, 01:37 AM
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
You can also make yourself an easy to follow diagram, like I do for the 4.5. In your case you start with 5 circles in a line (one for each cyl), in these circles place two smaller circles one filled in black the other just a circle. The black one represent exhaust and the circle intake (check your manual to be sure you have the correct ones in their location). Now as you roll the crank around, everytime a lifter is pointing away from a valve, adjust it and cross it off the diagram.

Makes the job easy, and you don't lose track of where you are at. Besides, the reason you are adjusting the clearance is so that they are not touching - they are just very close to touching.
Mike Tangas
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Old 09-07-2001, 06:53 AM
Registered Diesel Burner
Join Date: Aug 2001
Location: Northern Virginia
Posts: 2,911
I think most people here would advise you to turn the engine over either with the starter (careful with this - it might actually start) or by turning the engine with a big breaker bar using the CRANKSHAFT nut. Trying to turn over the engine using the power steering pully/nut puts too much force on the power steering pump in my opinion. It might be able to take it - but I KNOW the crankshaft can stand it.

I'm pretty sure you can turn the engine over as many times as you can stand to, it should not impact the adjustment of valves you have already checked/adjusted. Think about it - what's the engine going to do when it runs anyway? So if you miss getting one camshaft lobe & valve alignment just right, make a note and go on to the next one - come back to it on the next turn.

You bring up a good point about whether the table is right or not. My intention on the upcoming valve check is to just use the camshaft lobe position visually and NOT make any attempt to watch degrees of turn. The small side of a camshaft lobe is at the same height for a relatively large number of degrees - eyeball estimation of what's shown in the diagram should be close enough.

This comes from years and years of adjusting the valves on old Honda motorcycles - basically the same concept.

Are you aware of and did you get the helpful special tools for this job? You can do without them (so I have heard) but I got a pair of curved wrenches to make the job easier. Here's what they look like:
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Old 09-07-2001, 07:15 AM
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The chart that you're refering to has nothing to do with valve adjustment. It's a "cam timing" chart. It's lightyears beyond what you're doing...please, ignore it and just adjust the valves. You can spin the engine all you like in a clockwise direction. Just follow the firing order of the cylinders and you don't have to spin it more that a couple of revolutions. No need to read the marks on the balancer, just make the cam lobes face away from the rockers.
Randy D.
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Old 09-07-2001, 11:22 AM
Coming back from burnout
Join Date: Jun 1999
Location: in the Pacific Northwest
Posts: 2,274
To Everyone Above:Thank you very much for your help. When you get fatigued working in the sun, your mind and body go into "brainlock" and you sit there for hours pondering questions like these, getting nothing done. I was also worried about a piston smashing a valve and bending it so I had a terrible day yesterday..working on cars is usually very fun and relaxing......its good therapy for job stress. personal stress,and turning 40 stress

Richard Chang aka Carrameow
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