JekyllandHyde

iTrader: (3)

After driving about 200 miles on my new heads/cam/intake swap, I was getting really annoyed by the loud sewing machine noise I was getting and did a teardown of the valvetrain. I found that the bottom of my Comp Cams High Energy Die Cast aluminum rockers were rubbing on the rocker stud base. Here's my setup:

Trickflow 195cc heads milled to 62cc with guideplates
.030 thick GMPP head gaskets
TPIS ZZ409 cam with .525/.525 lift (.555/.555 lift with 1.6 rockers)
Stock GM Hydrualic roller lifters
Had to go with shorter 7.050 pushrods for thise setup
Comp Cams High Energy Die Cast aluminum rocker arms 1.6 ratio

When I took out the rockers, it looked like there was material ground away from the bottom where the rocker had been contacting the rocker stud. The coating on the stud had been ground away by the contact also. I thought at first it was too short of a pushrod, but we checked pushrod length multiple times and had the best sweep pattern with the shorter pushrods at 7.050. Any longer would cause the sweep pattern to ride more towards the exhaust side. I've heard of people having similar problems with Crane rockers doing this and they ended up grinding away the contact areas, but I'd rather not do that. Are there any rockers out there that have a wider slot on the bottom to accomodate screw in studs? Does anybody else have any suggestions as to how to fix this? Thanks!

JekyllandHyde

iTrader: (3)

Here's a couple of pics of what I'm talking about. First pic is the underside of the rocker arm and what was grounded away. The second pic is the mark left behind by the rocker on the stud:

TTOP350

iTrader: (8)

What heads?
Are the rockers self alining?
If they are you dont need guildplates.
you may need a longer pushrod. check the rocker pattern on the valve tip.

JekyllandHyde

iTrader: (3)

The heads are Trickflow 195s that were milled to 62ccs. The rockers are non-self aligning. I'm going to re-measure the psuhrod geometry. I think that a short pushrod coupled with the thick trunion all came together to cause the rub condition. Does anybody happen to know if the comp ultra pro magnums have a larger opening on the bottom?

Also, we verified the pushrod length and came up with the 7.050 length for the pushrod based on the sweep pattern we got with an adjustable pushrod. Could it be possible that the rocker was already bottoming out on the stud causing a false reading?

Hipster

Don't know how you set valve lash for it to run 200 miles with it bottomed out, but you really need to think about disassembly to get all the shavings out of the engine, A lot of heads run longer valves to obtain proper geometry with higher lifts, don't know what yours are set up with

JekyllandHyde

iTrader: (3)

Thanks for the responses, but I think we figured it out. These new rocker arms have a narrow slot on the bottom for the stud, so they don't really work too good with the screw in studs and guideplates. As far as the valve lash setting, we encountered a weird problem. Beause the body of the rockers was so big, the pushrods would get to zero lash, but then after the 1/2 turn, the rocker would seat onto the stud.

As far as disassembly, I don't think it's necessary. The griding happened on the drain side of the motor on aluminum, and the grinding looked minimal, so there's a good chance the oil filter caught everything. No oil pressure problems, oil pressure is same as it was. Aluminum is a soft metal and it looks like a lot of what was ground away would be aluminum dust. I'm just goint to drain out the oil flush out the motor with some diesel gas then change out the oil after a few miles again.

Damon

I'll let you in on a little secret about rocker arm geometry. You can't always get to optimum. Aftermarket heads are the worst offenders. And for exactly the reason you have encountered. They WANT shorter sticks to get the geometry right but the rockers bottom out on the stud radius before you can get there.

Aftermarket performance heads move things around in subtle ways vs. stock heads in many cases. And sometimes it causes a problem with getting to proper rocker geometry.

Why? Good question. I only have speculation to offer from my own experience. It goes like this: They assume that you are going to use full roller rockers since it's a performance head. Who gives a crap about proper rocker geometry if the rollers are going to survive some slightly odd angles in the lift curve? Oh sure, they make sure the rocker is not going to bind against the stud in the open or closed position but they don't seem to care nearly as much about how the tip of the rocker is oriented on the valve stem.

If I had only encountered this once or twice I could write it off as bad parts or bad design. But I've been down this road more than a dozen times. The answer (ugly though it may be) is to use sticks that are long enough to keep the rocker body from rubbing the stud radius and let the rocker-to-valve-tip geometry fall where it may.

I am sure you would like the "silver bullet answer" to your problem but you may find there is none. Having proper rocker geometry is great, but not if you're grinding rocker arms against the base of the stud to achieve it. Yes, "thinner" body rockers may work. But there are cases where nothing helps other than to buy longer sticks to avoid contact.

Most shocking example: AFR heads on my 454 big block. I currently have sticks that are +.500" over stock on the intake side!! AFR claims they need to be +.250" minimum with their heads. And they ain't just whistling dixie on that recommendation. The rocker geomety is HORRIBLE against the valve tip with those super-long sticks. But if the poly-lock is bottomed against the end of it's slot and the underside of the rocker is rubbing the rocker stud radius with anything significantly shorter YOU GOTTA GO LONGER. Period. End of sentence. No other option. So that's what I did.

And it runs like a top. Does everything it's supposed to do for several years now. Doesn't make me feel any better about the crappy rocker geometry, but it wasn't even going to surive otherwise.

I have numerous small block examples as well. And yes, a few of them involving Trick Flow heads.

Job one: sticks that are long enough to prevent grinding parts against eachother, even if proper rocker geometry is compromised. The ugly truth.

TTOP350

iTrader: (8)

One other option, mill the heads where the rocker stud bolts down. Yes you will have a lot to check b4 you do it but it is a option..

edit:
you could also grind the rockers 4 the needed clearance or mill the head, run a thinner head gasket and or mill the block.. but that costs decent money

JekyllandHyde

iTrader: (3)

Thanks for the insight Damon. I was hoping somebody who ran into this problem would chime in. I'm going to go the longer pushrod route. Do you ever worry about wiping out the valve guides though?

redneckjoe

i wonder if going to 1.5s would help any?

sofakingdom

iTrader: (1)

Ratio won't matter.

I'd mill the heads if they were mine... don't even have to take the heads off... you can do that on the car by taping over all the holes and just using an end mill in a hand drill with a suitable pilot or arbor. Doesn't have to be to any particular precise height, although it'd be best if you get the 2 bosses on each cyl as equal as practical so the guide plate sits flat; I'd shoot for getting around .100" off of them by the looks of the rockers.

Damon

I've not worried about wiping out guides since I am a good boy and run full roller rockers. With stock-type "scrubber" rockers I imagine there might be an increased risk of that, though.

BOOT77

Sry didn't read all the post, I had the same problem on a motor and fixed it with longer pushrods and lashcaps too keep the correct geometry.