Since running through CC last month and reading that cams with a small base circle and .530+ lift run the risk of spinning a lifter, I've be seeing that more and more. Is this old news or something new to sell us parts? I hadn't heard of that prior to the magazine article, and now it looks like it's all over the internet.

My roller has .585 lift on a small base circle with the stock lifters and hold down bars.

Is this mysterious .530 lift problem only from a certain RPM?

Has anyone had this alleged problem first hand?

What's the 'fix' for this?

 

i believe that they are refering to the stock type setup where the dogbone is used as the small base will drop the lifter deeper in the bore along with the high lift makes it even worse...

i think the fix would be to swap to link-bars

 

That's what I'm currently running, the stock lifters/dogbone.

From what I can see, the lifters aren't under the place holder, but I have no idea where they should sit in relation to it.

 

i think the only way to tell if you could have a problem would be to pull the intake and all of the pushrods and slowly turn the cam... i would get worried if any of the lifters werent atleast flush with the top of the dogbone when they are down in the bores...

 

The problem is, at zero lift, the lifters fall out of the dog bone.

Think about how they make a cam "bigger".... they DON'T do it by making the tip of the lobes taller, because they're already as tall as they can be, and the cam still be able to slide through the bearings to be installed. Instead, they make the "heel" of the lobe SMALLER, since "lift" is THE DIFFERENCE between the "heel" and the "nose".

A small base circle makes the "heel" even shorter, meaning the lifter descends that much further into its bore at zero lift.

I don't think factory machining on those blocks is ANYWHERE NEAR precise enough to specify very closely where problems will occur. However, it's a fairly safe bet that at some given .xxx" of "heel" diameter, x% of blocks will experience a lifter falling out of the dog bone; at .xxx" - .050", some higher percentage will have at least one lifter fall out; and .xxx" - .100", nearly all blocks will lose at least one. Or something along those lines.

Best thing to do, is to check how far your lifters go down at zero lift, and see if your particular block is going to be one of those first few.

 

The dog bone likely dances around a bit at high rpm too.

 

thats what i said