The rocker arm stud saga continues....
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Joined: Jan 2004
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From: Grayslake IL
The rocker arm stud saga continues....
So, as many of you have probably already read here on the forum we discovered a broken rocker arm stud on my Corvette when we did the Chicago tuning for Beer and hosted Lars. After ordering a new set of studs and getting them to compare to the old studs, I have found that the old studs rub the bottom part of the rocker arm. The new studs are tapered so that the rocker arm seats on the stud without rubbing at the base of the rocker arm. If any of you have Comp Cams Pro Magnum rocker arms, please lend me your opinion as I believe the new rcoker arm studs are the correct fitting.
Thanks
Thanks
Le Mans Master
Joined: Mar 2002
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From: Coming home from Luckenbach Texas
Ummm...I don't think the rocker arms should need to be adjusted so low that they're rubbing against the rocker stud. That could potentially be a pushrod length issue.
We'll let more expert opinions weigh in from here...
We'll let more expert opinions weigh in from here...
Pro
Joined: Nov 1999
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From: Front Range
Well pushrod length is going to be determined by valvetrain geometry and where the contact of the roller is on the surface of the valve. I'd say what's more of an issue here is that Comp Cams' rockers don't have the proper clearance to run on these particular studs. I'd try a different set of rockers with better clearance.
the blonde weasel
the blonde weasel
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From: Grayslake IL
Both good points. With the new studs the rocker arms no longer rub, they are tapered so the rocker arms seat on them. But is lifting the rocker arm up this much (I believe at most 1/4") going to throw off the geometry of the rest of everything else?
Le Mans Master
Joined: Mar 2004
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From: Little Rock AR
Think about this. When you modify a stock head to add screw in studs, you need to mill down the boss to accept the stud. You mill it a little further if you will also be adding pushrod guide plates. If your rocker arms are rubbing, you may need to cut the boss down a little to gain the required clearance OR use a stud that has a different base like you have on your replacement studs.
The arm may be in the right place in space but the boss on the head is too tall. Pushrods could be fine but here is another example of the need to always check valvetrain geometry on modified engines.
-Mark.
The arm may be in the right place in space but the boss on the head is too tall. Pushrods could be fine but here is another example of the need to always check valvetrain geometry on modified engines.
-Mark.
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Joined: Jan 2004
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From: Grayslake IL
Originally Posted by stingr69
Think about this. When you modify a stock head to add screw in studs, you need to mill down the boss to accept the stud. You mill it a little further if you will also be adding pushrod guide plates. If your rocker arms are rubbing, you may need to cut the boss down a little to gain the required clearance OR use a stud that has a different base like you have on your replacement studs.
The arm may be in the right place in space but the boss on the head is too tall. Pushrods could be fine but here is another example of the need to always check valvetrain geometry on modified engines.
-Mark.
The arm may be in the right place in space but the boss on the head is too tall. Pushrods could be fine but here is another example of the need to always check valvetrain geometry on modified engines.
-Mark.
Thread Starter
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Joined: Jan 2004
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From: Grayslake IL
What equation should I use to maintain specific parameters when dealing with my rocker arm studs in combination with my cam and rocker arms? My cam is a comp cam 268 XE and the rocker arms are comp cams 1.6 pro magnum full roller rockers.
I ask this because my new studs hold the rocker arm up about a quarter inch higher than the old studs, which will change the amount of valve opening.
I ask this because my new studs hold the rocker arm up about a quarter inch higher than the old studs, which will change the amount of valve opening.
Last edited by thevetterisbetter; Jun 1, 2005 at 04:34 PM.
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Verdad Gallardo
Pro
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From: Front Range
I didn't see you mention what valvesprings you are using. Make sure that your valvesprings can handle the extra lift attained by using 1.6 rockers. it could be that the spring stacked up all the way and provided enough resistance to snap the stud.
I'm not sure what you mean when you say the studs hold the rocker arm up higher than before. are you sure the rest of your valvetrain components are installed the same way as before?
another thing to be aware of is that on some roller rockers if you examine the central shaft, some will have one flat face and one rounded face (the flat face is what goes up, where the adjusting nut seats). is it possible you have the shafts installed upside down?
just throwing out as many ideas as possible
good luck
the blonde weasel
I'm not sure what you mean when you say the studs hold the rocker arm up higher than before. are you sure the rest of your valvetrain components are installed the same way as before?
another thing to be aware of is that on some roller rockers if you examine the central shaft, some will have one flat face and one rounded face (the flat face is what goes up, where the adjusting nut seats). is it possible you have the shafts installed upside down?
just throwing out as many ideas as possible
good luck
the blonde weasel
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Joined: Jan 2004
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From: Grayslake IL
Almost. I am moving slower because my right hand is out of commission (sledgehammer impact, don't ask). I have one side all changed and it seems to be okay, only I have one concern.
The 7th cylinder intake pushrod has very little clearance when looking directly down at it. So, if when looking at it in it's right position to the rocker arm, it's fine, but if, the pushrod makes it's up and down motion of travel by the camshaft stays in this exact location it's fine. If it moves "up" any it binds to the cylinder head, the cylinder head doesn't seem to have been ground enough to provide a lot of latitude. Should I be worried? Or do pushrods move only up and down the length of the pushrod and not up and down in the other sense?
I have not even tried to pass emissions yet.
The 7th cylinder intake pushrod has very little clearance when looking directly down at it. So, if when looking at it in it's right position to the rocker arm, it's fine, but if, the pushrod makes it's up and down motion of travel by the camshaft stays in this exact location it's fine. If it moves "up" any it binds to the cylinder head, the cylinder head doesn't seem to have been ground enough to provide a lot of latitude. Should I be worried? Or do pushrods move only up and down the length of the pushrod and not up and down in the other sense?
I have not even tried to pass emissions yet.
