setting rocker arms directly on valve stems??

[darwood300ex]

Hey guys, I was going to adjust my valves tonight and I have all the right tools to do it but I was just wondering about something. Can you set the rocker arms directly on your valve stems instead of putting the correct clearance between them? This is for a 2004 300ex with 1mm overbore and wiseco 11:1 dome top piston. I was thinking that this would give you A little more lift from the stock cam but I'm not sure if there are any implications as to weather or not this will affect my compression or other things like oil getting between the rocker arm and the valve stem. Any info would be greatly appreciated. also I was wondering if I did this would it cause my valves to hit my dome piston...

[rt20ps]

Once hot, your valves would not close completly causing a loss of compression. That is the reason they have lash.

[darwood300ex]

Yahtzee!!! I am glad I asked... Thanks

[darwood300ex]

hey, so what causes the valve noise "chatter" that you hear when the engine is running. I know it means they are out of adjustment but what exactly is causing the ticking. is it because the rockers are too far away from the valve stems and having the extra space in there allows for a louder clank when the rocker arm hits the valve stem??? I know this is in depth but i'm addicted to knowledge. This is a tightening effect on the valves if I am not mistaken causing too little flow. right?

[Sjorge450R]

the 300ex is notorious for making valve noise. A High compression piston also contributes to this. I know that doesnt help answer your question but its just a little insight.

[darwood300ex]

so I could be opening up for valve adjustment for no reason??? It is silent before it gets warmed up but once it is hot it gets pretty noisy... any suggestions???

[wilkin250r]

So far, your theory is dead-on.

In an ideal world, you would want zero gap. This is why you always set your valve lash while your engine is COLD, because the heat will cause the valves to expand and get longer, and close that gap to near zero (theoretically).

If that gap is too large, like you were saying, you get a "clank" Instead of pushing the valves open, you get an impact like a hammer. Not only does it cause more noise, but repeated impacts over time can cause damage, like dents in the rocker faces and a mushroom-effect of the valve ends.

But too little gap, and like rt20ps said, your valves don't get to close all the way. You lose compression and power, it won't run right.

Your situation sounds a little odd, I would think it's more likely to make noise while cold. But I would go ahead and open it up and adjust the valves anyways, just to eliminate that issue as a possible problem.

As for "This is a tightening effect on the valves if I am not mistaken causing too little flow. right?", the effect is only theoretical. You're thinking that more gap equals less valve lift, and you're right, but it's not that significant. The numbers just aren't there. Typical valve lift is about 0.350in, while typical valve lash is about 0.005in. Even if your lash was ridiculously out of spec, like 0.020in, you're still opening the valve 0.330. We're talking a valve lash WAY out of spec, and it's still less than 5% of the total valve lift. You won't see a significant difference in airflow.

[darwood300ex]

awesome reply man. Thanks for the info. I just get worried cause last time my valves started chattering I floated one and it stuck in the top of the piston. had to replace my whole top end...