Breaking Rocker Arms

6.0 Tech

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Got a motor i did for a buddy about a year back that keeps breaking rocker arms. We did the usual head studs, egr stuff, o ringed the heads, put an rcd stage 1 cam and lifters in, and now has their push rods as well (we'll get to that :doh:), regulated return, warren 190/30s, kc stage 2, bd exhaust manifolds, no limit intake and cac tubes, and csf intercooler. When the truck was first put together, i had elite pushrods in it, as he was sold them with the rcd am and lifters, and truck didnt run right at all. Finally found the pushrods were too long, and swapped in the rcd ones, and truck was good. About 2k later, it broke a rocker arm. I dont remember which one off hand, as its been a while. Figured what the hell, and put one in. About 500 mi later, it broke another, again, i dont remember which ome. Figured they were fatigued from having the long pushrods, and swapped all the rockers with ones off a core motor i had at the time. Trucks been fine for about 10k now, and morning he broke another, #4 exhaust it seems, as its popping out the intake. I havent torn it apart yet.

The core motor had about 180k or so on it if i remember right, and all failures have been at idle. First one he was in the drive thru, second, truck was idling while he was filling it up with diesel, and third was idling in the parking lot before he was gonna walk into work.

What am i missing here, that he keeps having issues? For what its orth, my truck isabout the same setup, except i have valve springs and bigger injectors, but ive put a bunch more miles on than him, and drive a hell of a lot harder, and am on original 215k rockers, and havent had any issues.

Thanks
 

imelmo

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When you installed everything did you put the dowel hole on the damper in the 6 0' clock position? When I broke a couple rocker arms in mine I saw some people saying that was necessary and some saying it wasn't. I did it just in case and haven't had any issues.

.
 

6.0 Tech

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When you installed everything did you put the dowel hole on the damper in the 6 0' clock position? When I broke a couple rocker arms in mine I saw some people saying that was necessary and some saying it wasn't. I did it just in case and haven't had any issues.

.

No, i didnt do that. Never have either, and havent had a problem. Except when i havent gotten pushrods fully seated in the lifter, but that bends the pushrod typically, and doesnt damage the rocker.
 

Zmann

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interesting

I am with you

i would always expect the pushrod to bend before a rocker broke unless the rocker was compromised or the pushrod was super strong but that's only if a valve stuck or there was contact between a valve and head these at idle occurrences are strange


but then again the 6.0 rockers are a little whimpy IMO
 
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golfer

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Was the block DECKED?

Decked...was the block decked/surfaced?

if so, what was the piston protrusion?

also...heads...if the heads were surfaced, what was your valve recession?

OE Cam?

Pushrod length?

if the cam is stock, and both the piston protrusion and the valve recession are in stock spec...then the only other possible issues would be pushrod length and/or valve stems dragging in the guides (slowly closing valves can be hit as the piston races back up to TDC and will shock load the rocker)
 

6.0 Tech

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Talked with my buddy today at work, heads were machined, but minimal was taken off, .003 was removed when they were machined, heads were original and had never been off, so I don't think there was an issue with valve protrusion, again just a guess, it was not checked. My heads had .005 taken off with no issue about 6 months prior to his being done, and were fine, until they started dumping fuel into the coolant. Valve guides ere not done, but the machine shop did disassemble the heads and completely cleaned them and inspected. Block was not decked or bored. Cam is an rcd stage 1 with rcd 6.4 pushrods now, the elite ones were about a quarter inch longer, as they were for a 6.0. That was the original issue, and were hanging valves open, which is why we also changed all the rockers after the first 2 broke. I figured they were fatigued from being held open and having possible piston contact from being held open. The valve guide issue makes sense though. Is there a way to check for dragging with the heads still on? The other thing that is kind of weird is that it has been a different cylinder each time. After talking with my buddy it was 2 exhaust the first time, then 6 intake, and now 4 exhaust. Thanks for all the help so far.
 

6.0 Tech

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He is now done being a cheap ass as well, and wants to put springs in it, will this help at least alleviate the issue of possibly sticking valves? Or will it just put more pressure on the rocker arms, potentially magnifying the issue?
 

powerstroked08

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Decked...was the block decked/surfaced?

if so, what was the piston protrusion?

also...heads...if the heads were surfaced, what was your valve recession?

OE Cam?

Pushrod length?

if the cam is stock, and both the piston protrusion and the valve recession are in stock spec...then the only other possible issues would be pushrod length and/or valve stems dragging in the guides (slowly closing valves can be hit as the piston races back up to TDC and will shock load the rocker)


What I meant about bored was that there have been times where the shavings got into the oil galley in the lifter bore. And if you don't get it out (I like to pull soft plugs and clean the oil galley) then those shavings can wedge the lifter in the bore and hold the valve open and cause piston to valve contact and bend a push rod or break a rocker. But absolutely yes on the deck issues.
 

Zmann

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yes you can check for slow valves with the head on if you can compress the valves/springs and release them fast ( lever type spring compressor is what i use )

I am working on a motor ( not a 6.0/6.4 ) right now that had two slow to close valves and 2 bent pushrods

it was repairable without pulling the heads


oh you can also air up the cyl and pull each spring then grab the valve with your fingers let the air off and see if the valve moves freely

just don't drop them i put a wire clip on the valve keeper recess
 
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DEEZUZ

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im finding alot of bent valves and bad guides...

Ive got one right now that I tore down for studs and had seen the piston made contact with intake valves at some point. Guides were bad and valves bent... also on that one, 1 of the 2 intake ports was 90% clogged...
 

DEEZUZ

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yes you can check for slow valves with the head on if you can compress the valves/springs and release them fast ( lever type spring compressor is what i use )

I am working on a motor ( not a 6.0/6.4 ) right now that had two slow to close valves and 2 bent pushrods

it was repairable without pulling the heads


oh you can also air up the cyl and pull each spring then grab the valve with your fingers let the air off and see if the valve moves freely

just don't drop them i put a wire clip on the valve keeper recess

Can also keep the piston just below TDC... thats what I have done on SBC's when changing valve springs after breaking in cams and such.
 

6.0 Tech

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This one broke weird, it snapped the pish rod end off, there were some cracks coming up from the pivot, which is where the other 2 broke, but this one snapped pretty clean at about the bend where the rocker kicks out to clear the injector. Ill see if i can get a pic on monday.

Didnt have anymore exhaust rocker arms laying around, but did have a set of 6.4 rockers, and the arms appear the same. So i threw a 6.4 exhaust rocker arm on, its been fine about a week now.
 

golfer

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Yeah, he doesnt have spimgs in it yet. He started ing a tightwad for some reason, and didnt want to put them in while t was apart.

(didn't re-read the entire thread again)...but didn't at some point one of the rockers break idling through a parking lot or something?

if so...I suspect there are other issues...the 'time to close' at idle/near idle rpm is soooo long that stiffer springs are probably not going to fix it..

worth a shot, I guess...as the other alternative is pulling the head(s) and measuring valve recession and piston protrusion.
 

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