The real "trick" to extended valve guide life is to have the roller tip of the rocker arm centered (or a close to being centered) over the valve stem as long and as much as possible as the engine operates.

If not, the valve stem will be side loaded in the guide resulting in accelerated guide wear. So the most desirable situation is the inboard, center, outboard, center, inboard cycling of the rocker roller tip.

You want the rocker tip to push straight down on the valve, not side load it.

This is one of the most ignored areas of engine assembly since the engine will run "okay" with pushrods that are a little too long or a little too short. It's what happens to the guides 'down the road', after lots of miles are put on the engine, that makes the difference.

Jake

 

I agree.Is there a reason, "inboard, center, outboard, center, inboard cycling " is any more desirable than, outboard, center, inboard, center outboard? To me, the side loading is the same. The proximity to the center is the same, only the direction of travel is different.

?????

RACE ON!!!

 

As long as the roller cross' the center of the valve and to each side of center, I think it's all the same. It just depends on where the cam is when you start the cycle. It could be center, inboard,center, outboard.

 

I have thought and re-thought until my brain turned into a pretzel. In therory it wouldn't matter, but what I was thinking won't work. I was never arguing that the convential thinking was incorrect, I just thought I had an alternate way of achieving the same thing. My idea is "all wet". Inside-center-outside-center-inside, is the ONLY way. Sorry!

RACE ON!!!

 

QUOTE]As long as the roller cross' the center of the valve and to each side of center, I think it's all the same. It just depends on where the cam is when you start the cycle. It could be center, inboard,center, outboard.[/QUOTE]

I believe it is in my second post where I identified the starting point for the cycle; lifter on the base circle (heel) of the lobe.

If you watch how the rocker cycles from the base circle position, you'll notice that the roller tip moves outboard then back inboard to the original starting postion.

It doesn't move inboard from the base circle position. So to get the least guide wear, with the lifter on the base circle of the lobe, the rocker tip should start inboard, etc. This gives the greatest average time of the rocker being centered (or close to being centered) over the valve.

Setting up the geometry in a different way will cause guide wear to increase and this, over time, will have a direct effect on how well the valve will seat on the head. How quickly this sets in is in direct proportion to how much the geometry is off.

In addition, oil comsumption will increase, as will smoking out the exhaust because a wobbly valve will wear the valve stem seal allowing excess oil down the valve stem. The backside of the valve(s) will show a buildup of crud (burned oil) which will hurt air/exhaust flow.

Jake