Cam Install Question

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agree with IQ52
to me straight up with a 110 lca is 110 ICL no matter how much is ground into the cam or not
some billets will not allow the grinder to put the ICL and excl where he wants it
and regrinds... have to fit the new lobe to what metal is available
agree on calling out the numbers
 
I've got a question about how to set pushrod length. I have an adjustable pushrod checker from Mancini.

But first I'll mention: With this particular cam I had to do as I said, and use the 6 degree retard setting on the Cloyes 9 position Street Billet set. Once I did this, EVERY number on intake AND exhaust opening, closing, lift, duration, ...ALL checked out within one or two degrees. And with exactly the 110 lobe separation angle, so all is good. And I end up with an intake centerline of 107* which I'm happy with. (cam card says 106*)

So next I need to order a new set of pushrods (from Smith Brothers) as my old set of Ersons are obviously too long. Since I am using a rebuilt set of stock 273 rockers how do I figure out length?? I have read that if there are about two threads of the adjuster showing then it's good.

Is what I go by??? (with the pushrods I have, the adjusters are screwed way up in with no threads showing at all.)
 
I'm not against using the 273 stuff, but if I already had a nice set of aluminum rockers, I think I would just get correct length pushrods. However, not all combos work out that well with the rockershafts in the factory location. Sometimes the rockershafts need to be raised for stability and long parts life. So I would check that out before ordering new pushrods.
 
Taking a close look as I turn the engine over the pushrods I now have make the rockers move across the valve tip out toward the end of the rocker pad. With the adjustable pushrod checker set shorter so there is about 1 thread showing and lash correct, the rocker works more in the center of the pad. And it looks like it is staying in the center of the stem better.
 
The M/P-D/C Engine Manual shows to set the adjuster screw to show 1-1/3 thread and adjust pushrod to put valve stem centerline and center of rocker pad in alignment at 50% valve lift.
 
Garrett Ellison said:
The M/P-D/C Engine Manual shows to set the adjuster screw to show 1-1/3 thread and adjust pushrod to put valve stem centerline and center of rocker pad in alignment at 50% valve lift.
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The only measurement I've ever seen in those books is 9/32 inch (.287). I've never seen any other number.

That is usually less than1 thread showing but the correct way to do it is measure it.

This is for a ball adjuster.
 
and the question is, which one haven't I used.
 
I've answered that many times on what I prefer. If I can get it, I use a Milodon gear drive. Or a belt drive. I cringe when I have to use a chain.
 
Thanks Guys!! I more or less knew this stuff once. :D It's coming back to me now, and I get what you're saying. Center/center at 50% lift. I do have the old MP "Bible" so will take a look at that as well.
 
My apologies, it was possibly Larry Shepherd's small block book but probably was an even older source I had somewhat committed to memory that I was quoting. But the correct amount of thread was stated as being 1/3 of a thread showing instead of 1-1/3 threads. DOH!
 
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midnight340 said:
Thanks Guys!! I more or less knew this stuff once. :D It's coming back to me now, and I get what you're saying. Center/center at 50% lift. I do have the old MP "Bible" so will take a look at that as well.
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If you want to understand geometry and not the crap that Chrysler put out back in the day, go to b3racingengines.com and read his tech pages.

In a shaft system, the only affect pushrod length has is the affect the length the adjuster hangs out affects rocker ratio.

Every correction has to be done with shaft location, and pushrod length is a function of that. Nothing else. That's why the actual adjuster protrusion is .287 inch.
 
The OP is using 273 rockers and not rollers, so some of the B3 info is not pertinent. The 273 rockers' pads:
  • walk/scrub across the valve tips from intake to exhaust side when going from 0 to peak lift (rather than rolling back and forth across the tip during the upward lift cycle like a roller)
  • the rocker ratio actually increases as approaches peak lift (rather than decreasing as it approaches peak lift as with a roller)
  • side loading on the valve occurs, unlike with a roller.
So some of the old Chrysler info is likely oriented towards that, and towards the side loading in particular. B3 does mention that sort of thing early in his articles, so gives some insight, but moves on to rollers.
 
you still need to do the mid lift procedure
depending on cam lift and valve tip height -with high lift cam figure half the lift increase between 340 cam and new cam and add to stock valve tip length- you will be real close - procedure definitely required with long valves- which allow bigger springs
"the adjusters are screwed way up in with no threads showing at all"
remember newer adjusters are longer between the last thread and the center of the ball- with these no threads are ok

"the rocker ratio actually increases as approaches peak lift" not if you have the line from the center of shaft to the pad/valve tip set with mid lift at right angles-perpendicular
max ratio is at mid lift

"walk/scrub across the valve tips from intake to exhaust side when going from 0 to peak lift" pad has a radius which mostly rolls across the valve tip
 
nm9stheham said:
The OP is using 273 rockers and not rollers, so some of the B3 info is not pertinent. The 273 rockers' pads:
  • walk/scrub across the valve tips from intake to exhaust side when going from 0 to peak lift (rather than rolling back and forth across the tip during the upward lift cycle like a roller)
  • the rocker ratio actually increases as approaches peak lift (rather than decreasing as it approaches peak lift as with a roller)
  • side loading on the valve occurs, unlike with a roller.
So some of the old Chrysler info is likely oriented towards that, and towards the side loading in particular. B3 does mention that sort of thing early in his articles, so gives some insight, but moves on to rollers.
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But it still matters. If you change on variable in the equation, the geometry needs to be corrected, no matter what rocker you use.

That could be lift, stem height or both. If you change one thing, it undoes what Chrysler did with shaft placement.
 
540BA4ED-8D52-4D0E-8605-37790BEFE2D8.jpeg
As accurately as I can measure, it looks like I have .140” between exhaust valve and piston with head on a “.028” gasket and head bolts snugged down till I get a bit of resistance with a socket. The gasket measures .035-.038” thick not compressed. Somewhat hard to measure the clay and not cause an indentation with the caliper.

How does this look for clearance? Seems I should be OK, correct?
 
Wyrmrider said:
"the rocker ratio actually increases as approaches peak lift" not if you have the line from the center of shaft to the pad/valve tip set with mid lift at right angles-perpendicular
max ratio is at mid lift
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Well, I measured the incremental valve lift versus pushrod movement in detail on a stock head and stock shaft position (675 head), and the rocker ratio did indeed increase as you approached the max lift. The rocker pad rolled/scrubbed across the tip and moved further out on the valve tip with higher lift. Just reciting some actual data; I am not convinced that it does as you think if adjusted as you described, but I'll admit that I have not checked it that way. How it contacts the tip depends heavily on the shape (curvature) of the rocker pad; the flatter the curvature, the more quickly the contact point is going to walk towards the exhaust side of the valve tip, regardless of the shaft location.
 
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midnight340 said:
View attachment 1715340770 As accurately as I can measure, it looks like I have .140” between exhaust valve and piston with head on a “.028” gasket and head bolts snugged down till I get a bit of resistance with a socket. The gasket measures .035-.038” thick not compressed. Somewhat hard to measure the clay and not cause an indentation with the caliper.

How does this look for clearance? Seems I should be OK, correct?
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That's plenty of clearance but the intake looks like it's damn close on radial clearance on the intake valve.

Also, did you do that with checker springs or the springs you will run. It makes a difference. If you used checking springs, you've got way more clearance than you think.
 
yellow rose said:
But it still matters. If you change on variable in the equation, the geometry needs to be corrected, no matter what rocker you use.

That could be lift, stem height or both. If you change one thing, it undoes what Chrysler did with shaft placement.
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Roger.... I wanted to point out that the 273 rocker does not work the same as a roller so not all of the B3 info is applicable.
 
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