Broke a rocker arm, replace the springs?

[digger]

why a new camshaft if no noticeable wear? jc.

I hope I don't have the same problem with OEM rockers. that would be unfortunate. I think if the same one broke twice I'd for sure be doing a head rebuild.

i've seen the MM ones as well, maybe they're worth a try if the issue repeats itself. that would suck.

"touch wood"... lol

best chance of breaking them in together if rockers and cam are new

[wakeboardr42393]

why a new camshaft if no noticeable wear? jc.

I hope I don't have the same problem with OEM rockers. that would be unfortunate. I think if the same one broke twice I'd for sure be doing a head rebuild.

i've seen the MM ones as well, maybe they're worth a try if the issue repeats itself. that would suck.

"touch wood"... lol

[digger]

It is. Ironically, however, the new rockers seem to be more prone to breakage simply
due to poor quality control. I had an especially hard time with the 2002-
getting a decent set of OEM rockers became an expensive proposition.

But then Ireland came out with the HD's for a very reasonable price...

t

the last two sets ive used are the MM inspected and peened rockers and so far so good..... touch wood

[TobyB]

aluminum is terrible in fatigue.

It is. Ironically, however, the new rockers seem to be more prone to breakage simply
due to poor quality control. I had an especially hard time with the 2002-
getting a decent set of OEM rockers became an expensive proposition.

But then Ireland came out with the HD's for a very reasonable price...

t

[digger]

So you're saying the aluminum just gets old and more prone to cracking over time?

And yeah, I probably should have them all replaced. this one's already ordered and hopefully almost here. if another one breaks I will consider doing them all as well as looking at the springs. i suspect i may have a teeeennnnyyyyy head gasket leak as well, but i'm not sure. if i do i'll noitce at some point. the thing that's making me wary of doing a full rebuild is that if i will be rallying the car, idk how long the thing will last. haha. i'd ranter have money to race and then risk having to repair it then not have enough to race and have a newly working car :P

some of you will like this lol: my gramps said they used to replace springs with the head ON. by connecting compressed air to the end of a compression tester, pressurizing the cylinder and keeping the valves closed.

I haven't taken the head off to replace a rocker. it's not hard with head on.

what would i do with the head rebuild anyways? I assume:

• rockers
• springs (after testing bad)
• valve stem seals
• valve grind
• all related gaskets
• timing belt

what am i missing?
is it reasonable/possible to get the top of the valves machined to get rid of the divot, so i don't have to do cam-side adjustment?

aluminum is terrible in fatigue.

add a new camshaft if all new rockers IMO

[wakeboardr42393]

So you're saying the aluminum just gets old and more prone to cracking over time?

And yeah, I probably should have them all replaced. this one's already ordered and hopefully almost here. if another one breaks I will consider doing them all as well as looking at the springs. i suspect i may have a teeeennnnyyyyy head gasket leak as well, but i'm not sure. if i do i'll noitce at some point. the thing that's making me wary of doing a full rebuild is that if i will be rallying the car, idk how long the thing will last. haha. i'd ranter have money to race and then risk having to repair it then not have enough to race and have a newly working car :P

some of you will like this lol: my gramps said they used to replace springs with the head ON. by connecting compressed air to the end of a compression tester, pressurizing the cylinder and keeping the valves closed.

I haven't taken the head off to replace a rocker. it's not hard with head on.

what would i do with the head rebuild anyways? I assume:

• rockers
• springs (after testing bad)
• valve stem seals
• valve grind
• all related gaskets
• timing belt

what am i missing?
is it reasonable/possible to get the top of the valves machined to get rid of the divot, so i don't have to do cam-side adjustment?

[TobyB]

Intake valves are smaller than the exhaust valves.

Jim got it backwards. I suspect a typo. Intakes are bigger and much heavier,
and the springs are all the same.

Intakes always break first. Only time I EVER broke an exhaust, the sucker had a void
in it the size or Texas. Said BMW on it, too...

If the head's apart, measure the valve springs. Replace the intakes if they're not
at least stock rating. Since, at 180k, you'll want to at least do valve stem seals and
you'll have the valves off anyway.

If the lash pads and cam don't look so good, now's the time to just bite the bullet and
do the head. It's not all that expensive, and it'll go another 150k- you can even stick
it onto another bottom end in a while...

jus' sayin'...

t

[digger]

Intake valves are smaller than the exhaust valves.

From what I've seen, my theory on broken rockers is that they fail due to a history of improper clearance (too loose). The repetitive impacts cause the rocker to eventually fail.

intake valves are 42mm vs 36mm for the exhaust which is a fair % mass. the heavier the valve the more shock (inertia) load you get if the rockers are not adjusted correctly.

[Earendil]

I just don't get why I seem to be the only one having this problem so consistantly (i've only had the car for about 7k km; less then 1 year). I have searched and have found zero cases where people have experienced 4 subsequent rocker arm breakages.

The reason is because standard procedure would be to replace all rockers at the same time. The are inexpensive compared to the labor, and no one want to end up breaking 4 rockers and paying the labor 4 times in a short period of time. Obviously, the equation change some when you are poor and do the work yourself. You have 12 rockers, they will all break given enough time, the question you face after losing 4 is, how long until the last 8 go?

Losing 4 in that short a period of time isn't written about often, but broken rockers in these cars IS for whatever reason. By design or not, given other problems, the rockers will break, and age and stress only serve to break them sooner. If you can spring for it, replace as many rockers as you can.

[plmichal]

I just don't get why I seem to be the only one having this problem so consistantly (i've only had the car for about 7k km; less then 1 year). I have searched and have found zero cases where people have experienced 4 subsequent rocker arm breakages.

I ran my m20 hard and snapped a rocker arm one time. Cylinder #4 intake. I replaced it and took it easy for a week. I slowly began to run the motor hard and within a month of replacing the first broken rocker arm, another one snapped. This time it was Cylinder #5 intake. I had done a valve adjustment prior to both arms snapping. I got tired and swapped in an M50 that month.

Had I kept replacing individual arms, I believe that they would have kept snapping. That M20 was fantastic and I wish I would've refreshed/rebuilt the head. If I were you, buy a rebuilt head or have your current one rebuilt with new parts.

[wakeboardr42393]

my rocker arm pads are pretty badly worn-



Yeah I don't think the previous owner kept the clearances set. It was pretty bad when I got the car.

Intake valves are smaller than the exhaust valves.

unless they are smaller in overall mass, which they may be for all i know lol, intake valves are larger at least in diameter then exhaust valves:

[jlevie]

I am replacing my FOURTH rocker arm on my m20b25. The engine is stock for all I know. The same one has not broken twice so maybe the rockers are just old. But then again, only the intake rockers have broken so far. and I know the intake valves are bigger, therefore heavier, then exhaust valves. are they floating? could they be floating bad enough that the valves would be hitting the piston, sending a shock back to the rocker, breaking it? if so, I don't want to just replace rockers to risk messing up the way the valves seat. like i don't want to ignore the real problem by just replacing rockers.

Intake valves are smaller than the exhaust valves.

From what I've seen, my theory on broken rockers is that they fail due to a history of improper clearance (too loose). The repetitive impacts cause the rocker to eventually fail.

[digger]

Would having excessively worn rocker contact pads do anything negative?

yes, the valve motion wont be controlled as intended which can lead to you know what if bad enough.

[wakeboardr42393]

I wonder how much lower the spring rate is then stock at this point. If it is a significant amount.

I just don't get why I seem to be the only one having this problem so consistantly (i've only had the car for about 7k km; less then 1 year). I have searched and have found zero cases where people have experienced 4 subsequent rocker arm breakages.

If this happens again, maybe I'll get springs for a single valve and have a shop measure differences between old and new spring rates. I'd post results. If pressures are significantly different between new vs old, buy a new set of springs. Valve springs are much cheaper then I thought they would be haha.

I just replaced the timing belt about 3k km ago. Today I double checked the timing, and it was ok. (the mark was like 2mm off but i suspect that's acceptable ;) ) I set the clearances a week before this arm broke to .010" on the valve side. I looked up cam side adjustment and I'm going to try it when this rocker arm comes in. makes plenty of sense. just seems like it'd be more awkward to get a feeler in there haha.

Would having excessively worn rocker contact pads do anything negative?

[CrazyJew89]

I second making sure your valves are adjusted properly. I'm pretty sure when I snapped my rocker arm it was from making them too tight. From the issues your having, and my assumption that you're on a budget, I would suggest getting some used low mileage springs and rockers, and look into cam side valve adjustments. Your valves probably have enough miles that they have developed a dish in the top of the stem making it impossible to get the right adjustment from the valve side.