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Discussion Starter #1 (Edited)
Now, I know we all run them... but , my question is, WHY? I run a solid roller,I run a button that I set at build, but, now, my inquiriry is this, WHY? Been there 4 years. Last week, I spent about a half an hour looking at cam and distributor gears and have decided that the gear on the cam pulls the camshaft to the rear of the engine block by way of the distributor and oil pump , againt the Torrington Bearing, between the cam and the front of the block. What would make the camshaft want to move forward? Is there something to ask my machinist... or should I give A S? Been about 15 years on two engines...Just Askin...Thanks for your time, Jack.
 

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Although turning the oil pump does create a rearward thrust in the cam, its isn't much of a force. And it doesn't "reverse" when you let off. The force merely lowers because the pump isn't as hard to turn. So it wouldn't be a matter of if you "let off " or not, if it won't stay in when you let off, it won't stay in at an idle.

Flat tappet cams lobes are ground with a taper that creats a rear ward thrust in the cam as it turns. This is what holds a flat tappet in place. Do you think they would bother if the oil pump could provide this. Many think this is to spin the lifter, and it does help, but the spin comes from the lobe riding off center of the lifter. I one lifter bore is slightly off from perpendicular to the cam on a flat tappet, it no big deal to keeping the cam in place. The force from all the other lifters will over come the force of just one.

But on a roller, all the lobes are dead parallel to the shaft. If one or 2 lifters are drilled ever so slightly leaning to the back of the block, the force is waaaaay more than enough to push the cam foward. Reguardless of the oil pump. The force from just one roller is incredible.

Sunkisst, I know you think you may have tripped over some unforseen discovery, but you didn't. There are many that fall into this belief. And many have had it work. Because the lifter bores in that particular block were fairly square. But the first time you run into a block that isn't, its going to tear stuff up. Also, even if the pump held the pump in place while making 60-70 lbs of pressure, it might move ever so slightly foward when idling. There is no way to know exactly where the cam is at any one time. And any movement in the cam will change you timing. So you can have a nice idle on time, and one quick rev, it idles completely different. I do not suggest running a roller without something that holds it back.



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Discussion Starter #5
And then what happens when you let off the throttle?
I didnt figure the slowing of the boat to make the camshaft still want to keep moving forward because of momentum, how stupid am I? GN7 thanks for your input. Never once had any thought of running without a button.
 

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I didnt figure the slowing of the boat to make the camshaft still want to keep moving forward because of momentum, how stupid am I? GN7 thanks for your input. Never once had any thought of running without a button.
I don't think anybody was inferring that the foward momentum of the cam would push it foward. Its that at low R's, specially after it is warmed up, the pump puts up much less resistence to turning, anf the force to hold the cam back drops considerably.

I glad to hear you are not considering running without some sort of foward control. GM is very aware of the problem, and put a foward cam retainer on all the roller cam motors. And they will trim a dime anywhere they can.

This explains the problem pretty well.

LINK: cause of cam walk



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Discussion Starter #7
I don't think anybody was inferring that the foward momentum of the cam would push it foward. Its that at low R's, specially after it is warmed up, the pump puts up much less resistence to turning, anf the force to hold the cam back drops considerably.

I glad to hear you are not considering running without some sort of foward control. GM is very aware of the problem, and put a foward cam retainer on all the roller cam motors. And they will trim a dime anywhere they can.

This explains the problem pretty well.

LINK: cause of cam walk
I was beeing a smart-Ass when talking about the cam moving forward on shutdown. I have seen the GM retainer. Thanks again for your time,Jack.
 
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