175whp

[darvo]

Any updates?

[nando]

what valve springs are you using?

The HD rockers are nice castings (internally, they're ugly on the outside) but if you're touching valves/pistons at high RPM, you need stiffer springs.

LOL at the comment of a stock M50 making 175whp...

[CarsSuck]

Did anyone notice this thread in the GD section?

http://www.r3vlimited.com/board/showthread.php?t=236804

You think someone floated a valve in an autobox 325i? It looks like the same failure mode, which was probably fatigue.

•And a broken rocker :/

[nando]

why not? there's nothing that forces an E30 automatic to shift up. if you leave it in 1, 2 or 3, it will be happy to hammer the limiter as long as you keep your foot into it.

[CarsSuck]

sure, its possible. But on a stock cam, with a stock redline? There's a big difference here, yet they broke the same way. HD rockers are definitely a good choice for his build, but I'm skeptical the he floated one valve and break one rocker...

[LJ851]

^ Perhaps that one valve had a little more clearance than the others. There are many variables.

[ForcedFirebird]

Spring age will do it too. Ever put a set of used springs on a spring tester? We have one at the shop, they will vary significantly. If one spring was weak, the valve could make contact on just the one piston.

We have had several broken rocker arms come through the shop, they always break in that same spot and the inside of the casting looks the same as the pics here. The only one I saw break in a different place was when the race car popped the HG and broke a rocker from detonation - that one broke at the shaft boss.

[nando]

sure, its possible. But on a stock cam, with a stock redline? There's a big difference here, yet they broke the same way. HD rockers are definitely a good choice for his build, but I'm skeptical the he floated one valve and break one rocker...

IMO, being stock makes it even more likely. redline really doesn't factor much into a broken rocker, if your spring pressure is adequate. the age of the valvetrain is a bigger technical factor - age of the rockers (aluminum is subject to cycle fatigue), age of the valve springs, maintenance & upkeep, etc.

[Fernflex]

I guess the problem was the rocker broke because of fatigue, my car is from 1987 and using the same rocker for 25 years using new valve, 288 cam ,higher compression, 7300 rpm and new valves springs the rocker didn't hold. Since day one I wanted to changed them but my mechanic didn't want me to spend more money.

My mechanic checked the clearance of each valves twice (first when installing the engine before first start up, second after a couple of month of use)

Before I change to MS my redline was 6,800 rpm

[nando]

oh man, yeah, bone stock rockers, 288 cam, 7000+ rpm? it wasn't a matter of if it would fail, but when.

think of aluminum rockers as having some X number of cycles before they will break. Maybe it's 1,000,000 or 10,000,000, but when it gets close to that limit, it becomes increasingly likely it will break, even if you aren't racing it. after 25 years, most of those cycles will have been used up. And increasing the RPM just uses them up faster.

[jlevie]

I've seen enough broken rockers on cars that I know spent little or no time at high rpm to have formed a theory as to the cause. I think that the primary culprit is a history of poor maintenance. Specifically a lack of timely valve adjustments. Excess clearance increases the impact force as the rocker meets the valve because the slope cam is slightly greater the more clearance there is. Worn valve guides may also be a contributor. Those repetitive impacts eventually cause failure.

Polishing the rockers around the failure zone helps because it removes stress risers. But going no more than 15k between valve adjustments is even more effective.

[nando]

I've seen enough broken rockers on cars that I know spent little or no time at high rpm to have formed a theory as to the cause. I think that the primary culprit is a history of poor maintenance. Specifically a lack of timely valve adjustments. Excess clearance increases the impact force as the rocker meets the valve because the slope cam is slightly greater the more clearance there is. Worn valve guides may also be a contributor. Those repetitive impacts eventually cause failure.

Polishing the rockers around the failure zone helps because it removes stress risers. But going no more than 15k between valve adjustments is even more effective.

definitely a factor overall, but even if perfectly maintained, I wouldn't expect 25 year old used rockers to withstand a schrick 288 at 7300rpm for very long.

[darvo]

Dyno Update?

[Fernflex]

Nothing yet, the idle is a litte high and we have to fix that also Im still waiting for the cam gear and the wasted spark.

[Exodus_2pt0]

Bump for info.