Discussion in 'Stage II Tech' started by Alky V6, Feb 18, 2012.
I'll get a shot of the bottom side of the retainer tomorrow.
I would think that the spring pressure would not influence guide wear that much if the geometry was correct. Clearance, oil lube availability as well as material selection of both valve and guide would be some of the variables to consider. Valve seat wear would be more interesting.
I agree, Allan. Geometry is very important in keeping rocker tip to valve tip side scrubbing to a minimum. As lift, rpm, spring pressure and cylinder pressure is stepped up, the geometry becomes critical to valvetrain durability.
Still, high spring pressures will wear the valvetrain, as a whole, quicker. That's inevitable. I would never consider wasting an engine, setup for high rpm use with heavy valve springs on the street. That's just a plain waste of bitchin engine.
Bottom shot of the Ti retainer and a comparison to the steel retainer off of the street spring setup.
The cross sectional thickness at point 'A' (red arrow) on the Ti retainer is .107". On the steel, .087".
The OD of the smallest shoulder of the retainer is .769" on the Ti, and .704" on the steel.
The inner shoulder of the Ti retainer fits the ID of the inner spring of the race spring with a nice press fit. This is the preferred fit to have to help control spring surge.
The inner shoulder of the steel retainer has a smaller OD than the ID of the inner spring of the street spring setup. This results in a sloppy fit between the retainer and the inner spring. Maybe on a street setup, spring surge is not something considered to be a main concern. The OD of the inner shoulder of the retainer is most likely small to save on weight. Or, the retainer is simply not the best match for this particular street spring, since a slight press fit on the shoulder of the retainer is preferred, for a racing setup anyway. Maybe there's a trade off going on with this particular street spring/retainer combination. Giving up a little spring control to save a little bit of steel retainer weight. Probably a good trade for a street application.
Here are some interesting pictures of the amount of valve shrouding there is with the Stage II head. Amazing heads.
The shape of the combustion chamber matches the cylinder very well.
A series of pictures showing the rocker arm geometry at zero, 1/4, 1/2, 3/4, and then full lift.
What you're looking for is to have the roller tip of the rocker over the middle of the valve tip by mid-travel. And, after mid-travel, stay very close to the middle of the valve tip.
The roller of the rocker is pretty far from the middle of the valve tip at zero lift, but spring pressure is also the lightest during that beginning and ending range of the valve opening and closing cycle.
Rocker arm geometry continued.
Some prussian blue dye showing the contact between the rocker roller tip and the tip of the valve at zero lift. The contact point is .100" in from the intake side edge of the tip. .072" out from the center of the valve tip. Well clear of the .030" from the edge of the valve tip considered by some to be the limit, and .022" further out from the .050" out from center that others consider the limit.
I think you need to shim the rocker shaft up some. If you color the top the valve and spin it over what kind of mark does it leave on top of the valve?
If I were to shim the rocker shaft up, it would move the rocker tip more towards the middle of the valve at zero lift, but would also move the roller out from center at all other lift positions. Keeping it more in the middle from mid-lift on is more important than getting it centered at zero lift.
Just finished watching Four Lions. Hilarious! Monty Python is alive and well.
From the pic you put up it looks like rockers are setting to low . But what do I know.
As long as I have the right rocker to retainer clearance, it will work. I'll be setting the retainer .050" lower than how the street spring was set up with this same rocker assm. and there was plenty of clearance with that configuration. I'm sure I'll be fine with this new configuration.
How wide of mark does it leave on top of the valve ?
I don't have an exact number, but I'd guess it's between .080-.090" from zero lift to full lift.
The rocker tip sits about .072" inboard of the center of the valve at no lift. I'm sure of that measurement. If you look closely at the pictures I posted, you will see that by 1/4 lift, the rocker tip has made a large move towards the center of the valve. By mid-lift, the rocker is very close to the middle of the valve, if not in the middle. Moving to 3/4 lift, the tip of the rocker moves outward away from the middle. Not much, but it moves out a little. By full lift, the rocker tip has moved back towards the middle of the valve. How far the rocker tip contact has moved out from the middle in the 3/4 lift range, I can only guess. No more than .020", I'm sure.
If I were to take a measurement of the sweep pattern from 1/4 lift to full lift, where the most spring pressure is being dealt with, the width of the pattern would be very narrow, as you can easily tell by studying the pictures.
Also, from 1/2 lift to full lift, the sweep pattern, never mind the width, would be concentrated very close to center on the valve stem.
Ok. It just looked A little to far to the inside to me. But you have A better view than me. I'm sure it will be fine.
Don. If those rockers have a stand height tool just use it. It's more accurate than the test your doing. The simple tool will tell you if it's dead on or not.
I don't trust those tools. To me, setting up the rocker geometry is like setting up a rearend gearset. You can use all the fancy tools in the world to setup the gearset, but the final test will always be checking the gear mesh pattern.
I tried using a tool that Jesel has for their rocker setup with the Stage I engine, and after using it I just thought, no way that's right. The contact throughout the lift cycle was no where near what they were showing me it should have turned out to be after using the tool.
Bottom line is, always visually check the rocker geometry, and know what you're looking for. Don't simply trust a tool and not check it.
Lol. It's not a fancy tool at all but it's way more accurate than what you are doing. I used to check geometry just as your doing but i checked it with the cam installed, lifters in place, using the correct length pushrods and valve springs. I would color the valve tip, roll the motor over then check the wear pattern, just as Chris described. It still isn't as accurate as t&d's stand height tool. My pattern looked good but stand height was off. I use the tool religiously now.
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