valve clearance with aftermarket cam/springs/valves...

[frosti108]

i looked in the manual when checking my valves the other day and it said something like .10mm or .004 inches i think but thats not important right now.

what i wanted to ask is should i still adjust to the stock valve clearance (what the manual says) or would it depend on what cam or what springs i have or something?

they click pretty bad but i think thats a 'given' with heavy duty valve springs and a fat cam...

btw its a stage 3 web cam... what should i adjust my valves to with it? should i go by the clymers manual for a stock 300ex or is there some special clearance i should be using for this cam or what...

help would be appreciated. thanks

[frosti108]

c'mon i know SOMEBODY on here has an aftermarket cam... i mean damn :scary:

[bwamos]

I run stock clearances on my MX Grind Cam. 5 years no issues.
Note: A snug stock clearance to reduce the noise.. just make sure it's not pushing the valve down and when the guage is removed you have some free play.

[frosti108]

sounds good man thank you :bandit:

[cals400ex]

the clearance you run is determined by which cam you run. call up web and see what clearance they recommend for that cam.

[wilkin250r]

Do you know WHY you adjust the valves?

As things get hot, they expand. It's a simple law of thermodynamics. The total AMOUNT they expand at a given tempurature depends on the material.

So what does that mean to your valves? As your engine heats up, your valves will actually get longer. If you set your valve clearance to zero, when they get longer they will actually stay open instead of closing all the way. So you set you clearance at some small amount (0.004 inch) so that your valves have room to expand. In theory, when the engine is hot, you want to your valves to expand to close that gap.

The actual amount your valves will expand depends on your valves, NOT your camshaft or springs. So your clearances should not change with your camshaft.

[bwamos]

Makes perfect sense.

FYI - Steel expands more than titanium. (about 15% more).

[400exrider707]

Originally posted by wilkin250r
Do you know WHY you adjust the valves?

As things get hot, they expand. It's a simple law of thermodynamics. The total AMOUNT they expand at a given tempurature depends on the material.

So what does that mean to your valves? As your engine heats up, your valves will actually get longer. If you set your valve clearance to zero, when they get longer they will actually stay open instead of closing all the way. So you set you clearance at some small amount (0.004 inch) so that your valves have room to expand. In theory, when the engine is hot, you want to your valves to expand to close that gap.

The actual amount your valves will expand depends on your valves, NOT your camshaft or springs. So your clearances should not change with your camshaft.

Just out of curiosity, why does hotcams recommend different valve settings with my cam than the factory recommended? Should I put it back to factory specs?:ermm: Thanks

[wilkin250r]

What are the hotcams recommendations?

[400exrider707]

stock as Im sure you know is .004 and .005 and hotcams recommends .005 and .006 those are for intake and exhaust respectively. Thanks

[wilkin250r]

0.001 isn't a huge deal. It's about half the thickness of a piece of paper.

The camshaft will also expand with heat, perhaps the additional clearance is due to different thermal expansion for their cam.

[400exrider707]

Ok makes sense. But everyone knows that the hotcam stage 1 is notorious for the loudest knocking noises in your head and for everyone it seems to be the "norm" but its always bothered me:ermm:
Thanks for the info

[MIKE400EX]

Wilkin, don't forget the opening and closing ramps of the cam. They too can affect valve lash settings.

[wilkin250r]

How? They will affect how FAST the valves open and close, but they won't affect thermal expansion of the end of the lobes that determine the closed portion of the valves, nor the thermal expansion of the valves and rockers themselves.

How would the ramps effect the lash settings?