Failed Rocker Arm

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After looking at those spring pressures it's no wonder the rocker broke... pretty strong spring for a stock rocker.

I usually use a spring that's around 130 on the seat and 335 or so open pressure. That's for a solid lifter deal running up to 7,000 rpm. The springs in my current 383 are 140/425 on a solid cam... about the heftyest I'd run on my W-2 heads.

FWIW...
 
I'll be popping out to the garage this weekend, see what I can find and get some more info and checking all the other rockers.

@nm9stheham, I'll take you up on that offer. Once I get out and get some measurements I'll post back here with what I find.

At this point, there seems to be a lot of recommendations for upgrading the rockers. Either that or downgrading the springs? If I do go that route, does anyone have any suggestions for what to go with? I'm guessing sticking with a stock ratio (1.6 I believe?).

Obviously I could get another stock rocker, install and see what happens. But I'd hate to have another one fail and have a much worse result. I was lucky enough this time that the small chunk that came off the valve didn't make it's way out of the head and down. If I'm at this point, and upgrading rockers is the best idea, I will probably go that route.

@TrailBeast, is there a link or info for which rockers you're referring to?

Once again, thanks everyone for all the info and suggestions, immensely helpful.
 
There is information all over the net about swapping in Chevy rockers onto 3/8 studs on Magnum motors.
I don't have specific numbers, but it is a common swap.
 
on those chevy rockes
arm length is all over the place
some are too short
and new pushrods
I'd ask B3
and rocker arm rebuilders (whatever) in Nor Cal
 
Never got the chance to get out to the garage to look at the situation any more.

@RustyRatRod, ouch...with exchange and shipping and taxes that's close to $1200 for a set of rocker arms....I think at that point I'd swap out the springs to the ones recommended to go with the cam.

@GEO, if only that were the case! With all the issues I've had with this engine I'm wanting to use it as a boat anchor shortly.
 
Let us know when you get an installed valve height..... you don't know what your pressures actually are 'til you get that measured.

BTW it might be worth exploring/thinking about what would happen to the engine if you had another rocker break. I've had a couple break like that with no different result than what you had. The parts are usually too large to go down the drain hole in the head or down the pushrod hole into the valley, from what I have seen. They just sit there. It is not at all like a valve or valve seat dropping. (But others may have seen differently.)
 
JRapley said:
Never got the chance to get out to the garage to look at the situation any more.

@RustyRatRod, ouch...with exchange and shipping and taxes that's close to $1200 for a set of rocker arms....I think at that point I'd swap out the springs to the ones recommended to go with the cam.

@GEO, if only that were the case! With all the issues I've had with this engine I'm wanting to use it as a boat anchor shortly.
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I agree, they are stout. However, they are bulletproof. Very nice. Probably overkill in your instance. A decent quality Chevy rocker is really all you need, but the only problem there is you don't know what you're getting, since you're using one application for another. At least with the Hughes shaft mounts, you're getting rockers designed for Mopar. Even the other pedestal mount rockers Hughes sells, are Chevy rockers, I do believe.
 
question is what chevy rocker? and which have the correct length from center of shaft to center of roller, which cause the pushrod to rub, which work with what ratio, etc
op first check and see if your valves are all thesame height with a straight edge
another person to ask is our resident crower expert pm dart19666
also see if there is a fit for their backset trunion rockers which would give more pushrod clerance and a better shaft sweep- also might work better if a high ratio is desired
in addition to rockerarms.com name now is "rocker arms unlimited"
but IDK if they do stud rockers
lots of bad chevy junk out there
 
Wyrmrider said:
question is what chevy rocker? and which have the correct length from center of shaft to center of roller, which cause the pushrod to rub, which work with what ratio, etc
op first check and see if your valves are all thesame height with a straight edge
another person to ask is our resident crower expert pm dart19666
also see if there is a fit for their backset trunion rockers which would give more pushrod clerance and a better shaft sweep- also might work better if a high ratio is desired
in addition to rockerarms.com name now is "rocker arms unlimited"
but IDK if they do stud rockers
lots of bad chevy junk out there
Click to expand...

Exactly my point. Some guys use the Ford rockers. Whichever.
 
I'm with you rusty
someone had a chart with all the fulcrum lengths measured
handy if using long valves or whatever
some companies sell one size fits all rockers for both chevy and ford, even give different part numbers to the same rocker
 
Howdy, we run a dirt circle track car. Did maybe 5 or 6 motors with magnum heads, as per rules no roller lifters or rockers. First one I did I called dave hughs and ordered a cam and components, asked him about rockers for this class and he said to run stock ones, they are tougher than nails. The cam he sent was like 600 lift, turnered it 6200-6400, 375lb at full lift,ran good.did 1 motor 625 or so lift ran it 7000 1 year. I have never had a valve train problem with stock mag rockers, thousands of laps. Did do one with comp chevy rockers it worked fine, had some money in that deal. Also I haven't seen a mag rocker with actual ratio of under 1.65 or so, get 2 dial indicators and check some, you'll be shocked. I think magnum rocker get a bad rap, geometry is poop but haven't broke one yet. These are claimed motors so nothing exotic.
 
JJ and Rusty are right on. To run a Chevy rocker on the Mag, the ratio needs to be 1.65. I put 1.6 Chevy Comp roller tips on a dirt engine and measured. Geometry was junk and lift was less than that of the factory stamped steel. Measured the factory steel rockers and the ratio was pretty damn close, taking the 59 degree lifter angle into consideration. We ran the stockers, with juice lifters, for a whole season with no issues. Open and closed pressures very close to what Krooser spoke of. One thing we did to the stockers was tig in weld some silica-bronze to close up around the "tang" on the rocker. Keeps more oil down on the spring and valve tips. Now he runs a solid lifter with the Hughes shaft mounts. Those things are bad ***!
 
stixx said:
I cannot picture how a broken rocker arm could have an effect on oil consumption other than it took out/damaged the valve seal or guide in the process.
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Your pulling on a closed system with no intake valve opening so your generating extreme vacuum inside the cylinder. your going to pull oil from the rings..Thats my thinking.

<<<Just read post 11, he said what I was thinking already>>>>>
 
JunkyJimmy said:
Howdy, we run a dirt circle track car. Did maybe 5 or 6 motors with magnum heads, as per rules no roller lifters or rockers. First one I did I called dave hughs and ordered a cam and components, asked him about rockers for this class and he said to run stock ones, they are tougher than nails. The cam he sent was like 600 lift, turnered it 6200-6400, 375lb at full lift,ran good.did 1 motor 625 or so lift ran it 7000 1 year. I have never had a valve train problem with stock mag rockers, thousands of laps. Did do one with comp chevy rockers it worked fine, had some money in that deal. Also I haven't seen a mag rocker with actual ratio of under 1.65 or so, get 2 dial indicators and check some, you'll be shocked. I think magnum rocker get a bad rap, geometry is poop but haven't broke one yet. These are claimed motors so nothing exotic.
Click to expand...

Well, the OP broke one. Bad rap or not. It's broken. So, I don't think he really cares what Dave has to say. I think he just wants a good solution. I've seen quite a few Magnum rockers break, so old Dave might be a little out of touch. He certainly is regarding slant six camshafts.
 
nm9stheham said:
Let us know when you get an installed valve height..... you don't know what your pressures actually are 'til you get that measured.

BTW it might be worth exploring/thinking about what would happen to the engine if you had another rocker break. I've had a couple break like that with no different result than what you had. The parts are usually too large to go down the drain hole in the head or down the pushrod hole into the valley, from what I have seen. They just sit there. It is not at all like a valve or valve seat dropping. (But others may have seen differently.)
Click to expand...

I would just worry about another rocker breaking and pushing down on the retainer instead of the valve. You could lose a keeper and drop the valve.
 
nm9stheham said:
Let us know when you get an installed valve height..... you don't know what your pressures actually are 'til you get that measured.

BTW it might be worth exploring/thinking about what would happen to the engine if you had another rocker break. I've had a couple break like that with no different result than what you had. The parts are usually too large to go down the drain hole in the head or down the pushrod hole into the valley, from what I have seen. They just sit there. It is not at all like a valve or valve seat dropping. (But others may have seen differently.)
Click to expand...

back from the dead! In the process of getting a shop built, so the repair has hit the back burner. Took other valve cover off and inspected all the other rocker arms and nothing seemed abnormal.

Measured height turned out being 1.562”. Which was from top of spring to bottom, on the valve that had the rocker arm break. Hopefully that’s the measurement you were referring to?

Thanks
 
JRapley said:
back from the dead! In the process of getting a shop built, so the repair has hit the back burner. Took other valve cover off and inspected all the other rocker arms and nothing seemed abnormal.

Measured height turned out being 1.562”. Which was from top of spring to bottom, on the valve that had the rocker arm break. Hopefully that’s the measurement you were referring to?

Thanks
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That seems low. Most of the time small blocks set up "around" 1.650, give or take. I think you should compare it to some others.
 
JRapley said:
back from the dead! In the process of getting a shop built, so the repair has hit the back burner. Took other valve cover off and inspected all the other rocker arms and nothing seemed abnormal.

Measured height turned out being 1.562”. Which was from top of spring to bottom, on the valve that had the rocker arm break. Hopefully that’s the measurement you were referring to?

Thanks
Click to expand...
Yes that IS low.... like .090" lower than stock IIRC. Which makes me wonder if the coils are getting reeeeally close to binding.... which maybe broke that rocker if it did. Coil bind looks to be 1.000" on those springs, and with the higher ratio of the magnum rockers and a 1.562 installed height, you're getting very near or perhaps a bit under the usual desired margin to coil bind.

I'd recheck that spring height on several. If true, then you gotta wonder if the retainers or keepers are off. Any shims under the springs?
 
I'll give it another double check tonight and look at some others. Just to be clear, that measurement didn't include the spring cap.

Out of curiosity, if the springs are getting to the point they're close to binding, is the solution different springs, different valves or both?

This engine isn't necessarily high HP & TQ (just shy of 400HP & 415lb-ft). I'm wondering if there would be any issues to just going back to stock springs.

@RAMM, any thoughts on this? I know you're fairly familiar with these EQ heads.

Thanks
 
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