Help rocker wear pattern w/ pics

seeya · Post by **seeya** » Mon Apr 20, 2009 12:15 am

I was recommended to this sight by a friend since I can not find the answer to my rocker wear pattern. Been trying to figure out why my pattern is only touching on one side to the valve tip. Currently have a set of Harland Sharp head specific rockers ordered and should arrive late this week.
I have set-up rocker geometry on Stock heads, Edelbrocks, AFRs, and Twisted Wedge Heads with no problems. The Highport heads were recommended and this is the first time I have ever seen this problem, I even tried with a stock h.o. cam, different rocker arms, and different length pushrods.
Here is the parts list:
SBF 408 new
TFS HighPort Aluminum purchased new
Comp Gold Rockers 7/16 1.6 new
Custom Cam new

I put the rocker arms on a friends car I set-up with AFR 185s

Guide plates adjusted as far as I could keeping the roller on the valve tip and on the other head

rustbucket79 · Post by **rustbucket79** » Mon Apr 20, 2009 2:03 am

Spin the valve a quarter turn and retest. If the pattern remains the same, the stud isn't parallel with the valve, (provided the rocker is machined correctly) if the pattern moves, the valve tip isn't perpendicular to the stem.

ProPower engines · Post by **ProPower engines** » Mon Apr 20, 2009 3:26 am

The other problem is the guide may not be straight in the head.
If the rocker is leaned away from the stud center it will be off like that.

Horndog · Post by **Horndog** » Mon Apr 20, 2009 9:35 am

ProPower engines wrote:The other problem is the guide may not be straight in the head.
If the rocker is leaned away from the stud center it will be off like that.

X2

The guide and rocker arm stud are not on the same vertical plane.

robert1 · Post by **robert1** » Mon Apr 20, 2009 10:05 am

This is normal for a stud setup. If the center line of the valve, guide plate, and lifter aren't all exactly the same this will be the result. Look at your rockers as they are installed and see if you notice that they are skewed in different directions. If so when they make their arc it will be off from the plane the valves travels.

95GTSpeedDemon · Post by **95GTSpeedDemon** » Mon Apr 20, 2009 10:25 am

robert1 wrote:This is normal for a stud setup. If the center line of the valve, guide plate, and lifter aren't all exactly the same this will be the result. Look at your rockers as they are installed and see if you notice that they are skewed in different directions. If so when they make their arc it will be off from the plane the valves travels.

So this is due to machining tolerances and when they get stacked up, this is what happens?

Will a offset Stud mount rocker fix this, or is shafts the only way, or does the head have to be fixed?

lets ASSUME the heads are assembled correctly, within an acceptable tolerance range.
The reason i say this, i have a set of canfield heads and i am having the same problem. Seeya and i also use the same rockers, comp golds.

robert1 · Post by **robert1** » Mon Apr 20, 2009 11:44 am

Some guys will cut the guide plates and move them around to better line the valve train and then weld them up. But if you're doing this you are moving something somewhere that doesn't want to be moved, i.e. you are moving the tip of the rocker off of the center of the valve. If the studs aren't spaced the same as the valves and lifters there's going to be a trade off somewhere.

ProPower engines · Post by **ProPower engines** » Mon Apr 20, 2009 11:44 am

In light of the new info I would thencompare the wear pattern to a different brand any brand of rocker to eliminate the rocker bodys/tips from being out of square.
Seems unlikely that two different head types would be in the same boat unless the rockers are the only variable.

95GTSpeedDemon · Post by **95GTSpeedDemon** » Mon Apr 20, 2009 12:25 pm

robert1 wrote:Some guys will cut the guide plates and move them around to better line the valve train and then weld them up. But if you're doing this you are moving something somewhere that doesn't want to be moved, i.e. you are moving the tip of the rocker off of the center of the valve. If the studs aren't spaced the same as the valves and lifters there's going to be a trade off somewhere.

I tried an adjustable guide plate on one cylinder (#3) and it did not fix the pattern. Out of 3 or 4 cylinders i moved the non adjustable guide plates on, one of the cylinders showed a huge improvement in the pattern, then of course the exhaust pattern was way off then. So using elimination i figured the guide plate was just not allowing enough adjustment. I now see that that's not the case entirely.

Seeya tried Trick Flow rockers and Crane Golds if i am not mistaken, and they did not solve the problem.

Im sure he will chime back in about it.

seeya · Post by **seeya** » Mon Apr 20, 2009 6:30 pm

In the first post I detailed the process of elimination with pics.
1. Used Comp Gold, Trick Flow, Crane Gold rockers
2. Pushrods in .05 increments from 7.65-8.10
3. Stud boss deburred with stone.
4. Guide Plates moved in every conceivable location.
5. Pattern is on all the valves, intake worse than exhaust.
6. Perfect mark on AFR 185 heads with the Crane and Comp rockers.
7. I believe the rocker body is rubbing the stud and not allowing it to sit flat during it's travel.

The Harland Sharp offset rockers are on order, but I am entertaining the idea of just cutting my losses and purchasing a set of AFRs.

95GTSpeedDemon is having almost the same problem with his Canfield 195's.

This is normal for a stud setup. If the center line of the valve, guide plate, and lifter aren't all exactly the same this will be the result. Look at your rockers as they are installed and see if you notice that they are skewed in different directions. If so when they make their arc it will be off from the plane the valves travels.

I'm pretty sure this is the problem...I wish I was made aware of this before I purchased the heads.

bill jones · Post by **bill jones** » Mon Apr 20, 2009 7:22 pm

-this previous sentence is most likely your problem

The other problem is the guide may not be straight in the head.
If the rocker is leaned away from the stud center it will be off like that

-If you take two 12" rulers and stand them up on the front or rear side of the valve stem and on the same side of the rocker stud without being affected by the studs lower radius-----and you view ANY vertical misalignment-----that means the stud holes and the valve guide holes are NOT machined parallel to each other.

-assuming you see there is a misalignment that means you'll need to remachine one or the other of either the stud holes or deal with fixing the guide and consequently the valve seat holes.
-----------------------------------
-all the changing around of the rockers and the guide plates will not fix the tilt problem.
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-Once you establish there is indeed a misalignment you should also be able to measure that misalignment in degrees--which is likely to be less than 2º.

-one degree of misalignment at the top of the 12" rulers would be something like .209" compared to the bottom.

seeya · Post by **seeya** » Mon Apr 20, 2009 8:06 pm

hmmm interesting method, I will look into this as soon as I get the heads back from the machine shop.
If that is the case then the heads are going back to the seller for fix.

jamie · Post by **jamie** » Tue Apr 21, 2009 9:14 am

I had a set of bbc 990's I bought as blems from Competition Products that had the same issue,these the stud bosses were machined/tapped crooked.I put them in the mill, drilled them parallel and installed thread inserts.Does your set of heads already have inserts?If not its a good idea IMO to have them anyways.

strokersix · Post by **strokersix** » Tue Apr 21, 2009 12:58 pm

It could be the studs themselves are not straight. That would be the easiest to fix, just replace them with quality parts.

540 RAT · Post by **540 RAT** » Tue Apr 21, 2009 3:08 pm

robert1 wrote:This is normal for a stud setup. If the center line of the valve, guide plate, and lifter aren't all exactly the same this will be the result.

I agree with Robert here. Production tolerances are such that a tolerance build-up can result in this situation. Welcome to the real world. Don't bother switching to AFR heads, because I've seen it on them as well. Also if you run a stud girdle, this can happen because its common for stud girdles to not fit "exactly perfect", particularly on a BBC's with their tilted semi-hemi valve setup.

Some may be shocked by this, but is it "really" bad enough to even worry about? I've seen far worse rocker geometry run on Hotrods and race cars without issue. It appears from the pictures, that the rocker and valve stem are not planar by some fraction of a degree, which isn't really all that much. When you consider the arcing and sweeping motion that the rocker goes through during its normal operation, this pushing down very slightly to one side, really isn't going to put side loading on the valve stem/guide, as much as the normal arcing/sweeping does. If that's all you have to worry about, you should consider yourself lucky.

A lot of parts in the Hotrod/Racing industry are made so bad, that this issue seems fairly minor. At least it will work, and if you were doing this motor for someone else, and didn't tell him, he'd almost certainly never even become aware of it. You could invest a lot of time and money, not to mentioin blood, sweat and tears, into switching heads, and you could even have the same issue there as well. So, I suggest that you consider running it as is and don't look back, since you are not alone with this deal. And you'd be hard pressed to ever tell the difference. Sure we'd all like things to be perfect, but we don't live in a perfect world.