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Eric had a nice diagram and explaination that you adjusted the valves when the timing was on the base circle of the camshaft, not the cam itself.
Does that mean the TDC for a cylinder is 180degrees opposite of the cam?
I presume that this means that you don’t have to exactly spot on the timing marks when doing the adjustment?
If anyone can clarify That would be great! Thanks!
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You’re right that TDC is 180 on the cam. When a 4 cylinder engine has 2 cylinders on TDC, one will be on the compression stroke and one will be on the exhaust stroke. Lets use #1 TDC as an example. That puts #4 at TDC of the exhaust stroke, and 2 & 3 will be at BDC for power and intake. The cam lobe smallest base circle is at the TDC location and the timing marks are critical to ensure that you are at the right location when you adjust the valves, as just a few .001 of lift of a cam lobe will make it so you adjust a valve too loose. This will cause premature wear from the impact, reduced power and a clattering noise.
To clarify my question and the reason I asked:
Yeah, I’ve only done 2 valve adjustments in my life on Honda 2.4Ls. More as a monkey moving parts around rather than understanding everything. I had been anal retentive about the timing marks, but the #4 cylinder was a pain to be sure of, because the timing marks are 180 degrees opposite of each other – rather than pointing at each other or directly up and down.
So therefore, now knowing this, either:
1) I don’t have to be so exactly precise of making the #4 timing mark exactly 180 degrees opposite. Oh 175 or 185 degrees should be ok ….Or
2) adjust both #1 and #4 at the same time. Since the marks TDC for #1 points at each other, it’s so much easier to know that you’re spot on.
Does this sound right?
You can’t do 1 and 4 at the same time since 4 would be at valve overlap of the TDC exhaust stroke and you would adjust it wrong. If the #1 is then rotated a revolution to TDC exhaust you could adjust #4 because it would be on compression.
Precise is the difference between a good repair and a comeback.
I think you’re being a little too anal retentive. As I said in the video all you need to do is be on the base circle, it doesn’t have to be ‘exact’ as far as the timing marks go. You just need to make sure that the valve is fully closed when you do the adjustment. In fact you can adjust BOTH the intake and exhaust when the cylinder is at TDC compression as both lobes will be on the base circle at that time. I don’t do it this way because I prefer to do the adjustment with the lobe pointed opposite the follower or rocker just to be 100% sure that I’m on the base circle but that’s just a personal preference. This is not necessary but it works for me and to me seems like a good rule of thumb when doing a valve adjustment. I think it’s even more important that you get the adjustment right because if you don’t then you run the risk of damaging the valves. Keep in mind that valve adjustments are a ‘fine adjustment’ and often have little effect on engine performance unless they were way out to begin with which doesn’t happen often. In fact the engine you mention doesn’t even have an adjustment interval, it’s just ‘when noisy’. You actually run the risk of screwing it up by adjusting it so proceed with caution and only perform the procedure when necessary.
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