potential engine damage with broken rocker.

[Jim Comet]

Last year I broke an intake rocker, I believe due to my adjustable rotor coming loose and sending my timing way off. I have now replaced the adjustable rotor with a conventional fixed rotor. I also replaced the broken intake rocker and push rod and the car finished the season running great. My question is, if an exhaust rocker broke, could there possibly be a potential for engine damage? I am considering stepping up from my Comp/Dove rockers to T&D's but am weighting the cost vs the potential damage that could occur if I broke another rocker, especially if it was an exhaust rocker. Jim

[GerryP]

What do you mean by "engine damage"?  Like broken bits dropping into the oil pan and locking up the pump, hitting the cam and gouging out a lobe, hitting the crank and punching out some cast iron?  Or do you mean that if the cylinder has an intake rocker that broke, what are the consequences there, or if an exhaust rocker broke, what are the behavior characteristics?

If it's the former, yeah, debris raining down into the crankcase can kill an engine.  Most of the time, it doesn't get past the cylinder head or cam valley, so it's a very slight risk.  Not zero, but small.

For the latter, many of us have had this occur.  On either the intake or exhaust, if you have a valve that doesn't open, you just get a dead cylinder.  Like a plug misfire.  It doesn't hurt anything.  I once had an intake rocker fail.  But my valve springs were on the weak side, so if I got the engine over 4k RPM, the cylinder would start to fire again.  Vacuum was strong enough to pull the valve open enough to get some air in the hole.

[DEANs427]

Biggest fear with broken rocker, if running pressure fed lifters, is the lifter jumping out of its bore and oil pressure then drops to zero at high rpm, pick up the pieces, ask me how I know

[gregb]

Well, about 30 years ago I broke an exhaust rocker about 90 miles from home, actually the shaft broke.  No where to get parts or fix it so I pulled the spark plug, took out the intake push rod (adjustables, it was easy) and drove it home with about 20 psi of pressure............(yes there was pressure, I'll thank the Ford Power Parts blueprinted HVHP pump for that)
Same bottom end in the car today............not a daily driver or race car though.
(yes, both lifters popped out of the bore, but with a whole lotta patience I got them back in without taking off the intake)

[Jim Comet]

I was mainly thinking if the exhaust rocker broke and the intake allowing an air/fuel charge in, firing it and having no where for the spent gas to go. Would the piston pound it and try and lift the head before the intake opens again and the spent gas reverberates up into the intake tract? I am running solid lifters with a link bar, so I think that is what saved the lifter from jumping out on me when my exhaust rocker broke.

[Nightmist66]

I had an exhaust rocker break cruising down the road. Sounded like a large exhaust leak, so pulled over. Started it for a short time to check for obvious signs and oil pressure remained same. Towed it home, pulled the valve cover and found the broken rocker on the exhaust, bent pushrod on the intake, and tossed lifter on the exhaust(flat tappet).  It will more than likely do what it did to me, just bend the intake pushrod, and/or break the intake rocker also.

Edit: Forgot to mention, the noise was popping back through the carb.

[Tommy-T]

I was mainly thinking if the exhaust rocker broke and the intake allowing an air/fuel charge in, firing it and having no where for the spent gas to go. Would the piston pound it and try and lift the head before the intake opens again and the spent gas reverberates up into the intake tract? I am running solid lifters with a link bar, so I think that is what saved the lifter from jumping out on me when my exhaust rocker broke.

It's scary as hell when an exhaust rocker breaks. Engine missing, popping back through the carb every other revolution it sounds like the whole shittery is blow'n up! Back when I was 19 I decided to drive my '63 Falcon Sprint with a "built" 289 to Springfield Illinois from Los Angeles for the Street Machine Nationals. It was about 2AM and we were about 40 miles west of Albuquerque New Mexico when a screw in rocker stud busted for an exhaust valve. My friend was driving, it was dark, and we were far from home.

He quickly went into panic mode. What do I do he shouted. I tried to keep my composure and said "as long as this thing will drive forward, keep going". We made it to a Super 8 motel on the outskirts of town and slept. The next morning I pulled the valve cover and saw what it was. Luckily there was an auto parts that had some studs. Fixed it in the parking lot and we were off to Illinois. As far as I could tell it did no damage to the motor, but I puckered so hard I think I did damage to myself.