Correcting Valvetrain Geometry 12 Valve

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Aug 6, 2011
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I was just getting around to measuring for pushrod length and checked my rocker to valve contact area and it looks like it has "over shot" the center of the valve. Ever where i have read online says to run a shorter pushrod but not sure how that would even help but just over extend the adjuster on the rocker. So any thoughts or ideas of what people have tried to fix it?

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Harland Sharp makes some really nice roller rockers available in different ratio's. Salty price, great product.
 
Swapping a a different set of rockers with different ratios wouldn't fix the contact area on the valve. Shimming the pedestal or lash caps in a few cases i have seen but wondering if anyone has dealt with it at all or does anyone ever bother to check at all?
 
Was this just a contact spot or did you roll the engine over and run the valve through it lobe cycle?
 
Rolled over a few times and tried it on every stem had about the same results.
 
That's not too bad. The only fix is to raise your rocker pivot point (shim up).
With the low rpm/spring pressures of the motor, I wouldn't worry too much about it.
 
More than likely through valve seat/face machining, the valve has been sunk a little deeper than stock specs.
Causing a higher valve stem which in turn throws your geometry off slightly.
 
when considering proper geometry it's not just rocker ratio or push rod length, but Valve stem hight, seat depth, cut, ect (+/-). Sometimes push rod length wont get it done correctly.

custom valves cost more, but if your worried about geometry then this is the right direction.
 
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destroked 99 said:
That's not too bad. The only fix is to raise your rocker pivot point (shim up).
With the low rpm/spring pressures of the motor, I wouldn't worry too much about it.
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185 seat pressure and 600 spring rate pressure on a motor built to handle ~5500rpm I'm gonna worry about it. Does anyone make a shim for pedestal mount at all or would i have to fab them up and have an alignment dowel made up? Wouldn't i be safe to run lash caps to increase valve stem height?
 
I'm talking 250-300 seat pressure, 850-900 over the nose 7500 rpm gas stuff. I've ran sweep patterns worse than that ( not because I wanted to) and not be the worse for wear after 200 plus passes.

Your stem height is high right now so lash caps aren't going to help. I don't know about shimming your pedestals, it could be done but it would take some work.

Diesel Power said it all when he talked about custom valves. You either need a lower valve stem height, or higher rocker pivot to move your sweep closer to the center of the valve tip.

Check your valve at seat, half lift, and full lift. Where is the rocker contacting the stem at each point? It should sweep from rocker side to valve side and back.

Not at all trying to be an ass, but google shaft mounted rocker geometry. Big block mopar, ford, and a lot of your high end rockers ( TD, Jesel, Harland sharp etc...) are shaft just like a cummins. A lot of good info out there. Wish I had a magic wand to wave and give you an easy fix.
 
Man your gunna cuss the piss out of me. I had a major brain fart. Way too many hours at work, not enough sleep= dumbass!!!!
You need more stem height. That will move your sweep point starting closer to the rocker side of the valve, but is isn't going to fix your sweep width.
 
destroked 99 said:
Man your gunna cuss the piss out of me. I had a major brain fart. Way too many hours at work, not enough sleep= dumbass!!!!
You need more stem height. That will move your sweep point starting closer to the rocker side of the valve, but is isn't going to fix your sweep width.
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No offense taken at all. Everyone seems to have different opinions on what a lot is and i just based it off of stock was. Id dealt a lot with adjusting the shims for small block mopars to get it set up right but they had no room for Lash caps. It has the sweep on all of them but 2 intakes. Which just makes me think the pedestals aren't entirely true to being machined. Just my first full diesel build where i keep double checking everything over and over and second guessing myself. Done a dozen or so small block mopars and checked everything time and time again. Just not a topic that is covered at all on here or the search is broken... lol
 
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