Originally Posted by superd
First off,, there are no clearance ramps...
The only clearance is on the BASE CIRCLE of the camshaft.....
Not on the ramps of which there are opening and closing ramps....
And there are MANY more to chose from.
Second...Do you really think a few thou makes the difference between
gasses moving at super or subsonic speeds?????
Absolutely. If the valve is being opened on the low rate clearance ramps, the gap between the valve head and seat is small for too long. The high combustion pressures cause the hot gas to stream out at higher speed until the valve opens a little further, then the flow can slow slightly. Supersonic speeds of hot gas erode seats much faster than subsonic speeds. I did take fluid dynamics years ago, and this is elementary.
It was a poor choice of word. It is really small eroded lines that appear like cracks, but are surface only.
Metallurgy on valves is such that they can stand exhaust heat by A LOT...
Not just a small amount..... Warranty testing anyone...??
Ever check valves on a HOT engine??? GEEZ,are they different????
Like I said.. manufacturing tolerances and heat....
As I said, manufacturing tolerances have NOTHING to do with valve lash settings. The ADJUSTMENTS made to achieve the proper lash are what makes up for the manufacturing tolerances, NOT the required lash.
Did you know hydraulic lifter systems technically run with no lash or virtually
Well, yes. Doesn't everyone? Cams for hydraulic lifters are ground DIFFERENTLY than for mechanically adjusted lifters. The clearance ramps, which cannot be totally done away with, are made as short as possible for hydraulic lifters.
I have personally run valves on k engines .003 too tight and they stayed that way for 100 k plus miles more than once and guess what no problemo...
And still running....by the way....
If you run them a little tight you will be decreasing the on seat time by an
extremely small amount time wise... emphasis on extremely....
And emphasis on time cause that's what we're talking about...
It is not the total seat time that we are talking about here, it is the time that the valve is barely cracked open. Engine designers try to keep that at absolute minimum, and want the valve to open rapidly as soon as it starts to move. They do NOT want the valve to start opening slowly, as they do if adjusted too tight, and start opening on the clearance ramp, which is a much slower movement than the actual opening ramp.
Not enough to make any difference you could measure....
If they didn't close then you have a problem.. no seat time...
I don't just assemble them but, could MAKE you any part you need for an engine....Yes really...
That means little. I was a Tool Maker for quite a few years also, before I went back to school to become an engineer. I could make parts too when I was a Tool Maker, but that did not mean I understood the engineering behind them. Wanted to though, so I went back to school.
The central idea is I said I have let them go at .003 tight but it's probably
a good idea to take some action..but at .002 I wouldn' sweat it...
I sure hope no one here actually starts letting their valves go tight based on your statements! They are way too easy to just set correctly than take a non calculated chance on needing an expensive valve job way before it's time.
And yeah,the FACT that I've seen this to be true for so long on so many engines.. doesn't mean anything RIGHT???
I spent about 8 years involved with drag racing engines back in the late 1960s. People were purposely adjusting valves tight to gain a little opening time. Slightly increased power, greatly increased incidence of burned valves resulted. The smart ones learned fast, and stopped that practice!
Engineers are good and bad right?? Didn't they design the vega??
Yes, there have been some engineering mistakes made in every engineering field known to man. Some really tragic. Fortunately, they are minute in comparison to the engineering successes. Engineers, and the engineering community learn from the mistakes, and continuious improvements are made because of that learning. If valve lash settings being widened would make any improvement at all, and not at the expense of reduced life/reliability, the automotive engineers involved would likely do so. It would reduce manufacturing costs if the settings could be widened.
By the way, we built some of the die cast dies for the Vega engine block..
And yes it was die-cast...
A little tight and still running...Ran all 5 nevada 1100's w/ valves a little tight and still have the same bikes...Guess I just got lucky ....
Why not adjust them within .0002 if you need to be safe....
When you get back from the bureau of standards recalibrating your feeler
gauges..let everybody know...
I have tried not to make ridiculous statements, I see you don't have that will power.
I'm not saying you're a bad guy.. heck, I don't even know you..
We disagree on this issue...
I have no reason to think you are a "bad guy" either. I just think you have been lulled into complacency by good luck, or perceived results that may not be real if you were to examine the valves and seats on one of these engines that has run tight exhaust valves for an extended period.
Bet we all can't wait for the fire storm after this one... yyyeeeeeooowwww!!
It will not be much of a storm, just a couple smoking embers. The great majority of people will just go on and adjust valves to manufacturer's specs, since there is practically nothing to gain by not doing so, and a reasonable probability of future problems if they don't. Most reasonable people will not take the chance.