175whp

[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]

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.

[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.

[LJ851]

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

[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...

[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]

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]

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...

[darvo]

Any updates?

[Stephen]

Awesome to see a diy ITB setup done through to the end. Jealous.

[digger]

i cant see 100% but in this particular case that looks like overload failure rather than a small crack propogated by fatigue which sunsequently grew to a size that caused catastrophic failure. This goes away to confirm that valve bounce could be the main factor factor which while an obvious conclusion it shows that peening is not a huge benefit against this mode of failure. The casting quality seems inferior to the original BMW rockers i have with me but it may just be the pics. The MM testing showed some rockers were 30% stronger in a single static test.

[Fernflex]

Stock


HD

[Fernflex]

Ebay Headers, Big Valves, Itbs kit.



HD Rocker Arms

[darvo]

No prob!

Tomorrow they will replaces all rocker arms and installe the new heavy duty with the bigger injector and going to wait for the wasted spark to arrive to go back to the dyno.

Darvo: sorry I didnt call you, my mech planned everything and he didn't told me until the last moment.

[ForcedFirebird]

You ran the stock single coil over 7500RPM? Bet it was real happy with that lol.