Mark D 6900RPM chip vs stock rockers

[funcrew]

Engine is a stock M20B25. What's the likelihood I'll blow up the stock rockers by raising the redline from 6500RPM to 6900RPM? I autocross, so the rev limiter does get used a bit.

If the chances are not favorable, what's the minimum rocker upgrade that will be reliable at that level?

Any other issues I should be thinking about?

Thanks!

[Hallen]

I asked Mard D that question and he wasn't concerned about it at all. That's all I know on the subject.

[nando]

your rockers are more likely to fail just from old age and fatigue, poor adjustment or $shifting than they are from a high redline.

also, for autox I'd rather have a much higher redline and avoid bouncing off the limit, rather than one that forces me to hammer on it for long periods of time. That's part of why I set mine over 7,000.

[Hallen]

Yep...

More info on it. Blipping over the red line and $shifts along with weak springs cause a lot of them. RPM's alone don't always do it. That guy whill really knows what he is talking about, trust me.

http://www.bmwpugetsound.com/vbb/sho...threadid=13671

[e30cbe]

Engine is a stock M20B25. What's the likelihood I'll blow up the stock rockers by raising the redline from 6500RPM to 6900RPM? I autocross, so the rev limiter does get used a bit.

If the chances are not favorable, what's the minimum rocker upgrade that will be reliable at that level?

Any other issues I should be thinking about?

Thanks!

From what i know many pattern rockers do not have the quality of oem rockers - i know a few who have raced pretty wild m20s and oe rockers have not posed problems at much higher rpms than standard - also the cam lift and valve spring pressures have a lot of bearing on the reliability of rockers not to mention usage style - miss shifts etc

[Erick]

your rockers are more likely to fail just from old age and fatigue, poor adjustment or $shifting than they are from a high redline.

also, for autox I'd rather have a much higher redline and avoid bouncing off the limit, rather than one that forces me to hammer on it for long periods of time. That's part of why I set mine over 7,000.

Curious argument, because I never had any luck with going past 6500rpm. My motors were in very good shape, which if you're correct, then my valve adjustments (.010 cold) must have been the problem.

[nando]

what's good shape though?

and a lot of the rockers had poor castings with big holes in them. Worn springs will also contribute (valve float).

[e30 gangsta]

I had the 7100 rpm chip for over 4 years. With multiple track days i never saw a issue.