So I broke a rocker arm at RA...

#21

Nothing you’ve written suggests that your head is/was cracked.

When a rocker breakss the valve stays up so there’s no chance of the valve damaging a piston. If you luck is bad, a broken piece of rocker could damage another rocker or the cam. Or could send metal shards down into the oil pan.

Remove the front sheetmetal and rocker arm shaft retaining pin. Then patiently wiggle nudge and push the intake rocker arm shaft forward until you can replace the broken rocker.

If exhaust rocker is damaged then do that one too.

Most likely cause was loose or mis-adjusted rocker eccentrics. 2nd possible cause could be voids in the rocker casting as you described.

I think that it is common to re-adjust valves after a head install. For example…install the head and adjust the valves. Run for a weekend and then check the valves again.

#22

The coolant and oil mixing under the rocker arms is a good sign the head is cracked. Unless coolant can get in from someplace else?

I ran on the street for a few miles, less than 100, didn’t even get one full track day in before I heard a huge bang and had even less power. Never did find all the pieces…

#23

OriginalSterm wrote:

[quote]The coolant and oil mixing under the rocker arms is a good sign the head is cracked. Unless coolant can get in from someplace else?

[/quote]

Ah, I misunderstood that part. Certainly that sounds like there could be a crack in the head’s waterjacket. Might want to drain the oil and check to see what it looks like. Doesn’t take much water to contaminate all the oil.

Hard to understand how a crack would break a rocker unless the crack allowed the cam or rocker arm shaft to bow. Hard to understand how a broken rocker would crack a head.

I’m hoping that it’s only a broken rocker and the head turns out to be otherwise ok.

#24

Ranger wrote:

[quote] Hard to understand how a broken rocker would crack a head.
[/quote]

I’ve heard that when the old style head bolts break it’s possible for the head to be punched into the water jacket by the cam lobes. I have no idea if the same thing could happen with rocker parts floating around, but I’d guess it could.

I’m with Scott in hoping that you can just replace the rocker(s).

Matt

#25

I have the hex head style head bolts. But my theory as to why I may have a cracked head is that when the rocker broke it got wedged between the rocker arm and the valve spring leaving the valve open longer than it should have been. It’s just a guess, but I haven’t found all the pieces of the rocker or eccentric yet, probably in the oil pan…