Rocker Ration

I have a question regarding rocker ratios..

I understand how with a 'stock' cam high ratio rockers make a difference in valve lift, basically increasing lift. That makes sense.

With Engle cams I notice they make several different grinds some which are incredibly similar (if not the same) but use different ratio rockers.

What's the advantage either way?

Rather than spend big bucks on high ratio rockers why wouldn't I buy 'good' stock ratio rockers and use the corresponding cam grind?

I was planning my motor out and wondering about this.

Dan

Reply to
bcdlr
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Main reason:

if all the lift is built into the cam, the lifter will need to move more. Problems start developing when huge lift cams are made with small base circle, the lifter has to come way out of it's bore to follow the cam when it gets "off" lobe. The cam then turns and reaches a point where the lobe starts pushing the lifter back into its bore, but because of the extreme angles and sudden lift, the lifter is pushed sideways too. With very little lifter body left inside the bore as guide, the whole lifter begins to tilt at an angle while it is being pushed in. This starts wearing the lifter bores out pretty fast. It also involves a problem with lifter bore lubrication, the oil holes in the bores don't spend a whole lot of time lined up with the lifter grooves to begin with. With high lift cams, you make the lifter move further away from the oil hole every time it completes a cycle, so during the cycle it spends less time (distance) lined up with the oil hole. Bob Hoover has written a great set of tech articles addressing lifter lubrication modification that addresses this problem (The "HVX Mods" articles.. read it all before doing anything, they are a *set* of mods that pretty much only work together. Sorry, no link available at the moment)

More:

the lifter, pushrod and rocker are WEIGHT that need to be thrown back and forth. if you can make the weight lighter, you make the engine lighter to run, it revs easier and has less internal resistance to "waste" horspower on. But there's only so much weight to be saved with the mass of these parts themselves. Shortening the movement with less cam lift gives the moving parts less distance to travel. Basically, less weight, and momentum to overcome when you need to reverse the direction of movement every time the cam lobe swoops by. The lost lift is gained back with ratio rockers. Less energy is used for creating movement. I think.

this is at least how I understand it.

Jan

Reply to
Jan Andersson

HHHhmm, silly me, I thought we would be starved soon.... :o)

J.

Reply to
P.J. Berg

Okay, okay... my mind was stuck on rations when I should've been typing ratios...

Here's one of the Hoover links:

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's some another:
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Got some reading to do. Simple mods to the lifters, BTW. But wouldn't want to drill the case!!

Dan

Reply to
bcdlr

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