[AmuroRay]

By changing the N52 to the N55 rockers, I calculated 10mm of lift.

[AmuroRay]

Originally Posted by CobraMarty

Wow, where have I been?

Bnks334 and mikeseli contributions are very helpful.

I have 4 exhaust cams.
Used N52, N54, N55
New 'russian' sourced N52
I sent them out and had than all 'cam doctored'.

From all of this, what I find most interesting is the different part numbers for the N52 and N55 rockers. It would be great of the N55 rockers were higher ratio than the N52.

So if that is the case, I believe there is some merit to these power gains with using the N52 cam in the N55 engine.
This will add +0.3mm lift and +1* duration just from the N55 rockers with more ratio. Add that to the slight increase in the N52 duration, maybe you see +0.3mm exhaust valve lift and ?+5-7* duration.

This additional lift and duration using the N52 cam and N55 rockers would not add much peak power but will extend the powerband. That is exactly what is seen especially above 5000rpm. This makes for more power under the curve and more top end pulling power.

Yeah I call BS on +90-100 hp gains when the 'gain' is when compared to the stock drop off in power above 5000rpm.

If in fact that N55 rockers are 1.72:1 compared to the N52 1.66:1, I might just swap in a set of the N55 rockers into my N52 engine. Costs about $200 for +0.3mm lift and 1* duration on a N52.

I can post all my cam data sheets if need be.

This was said

[Island Road]

Originally Posted by AmuroRay

This was said

Did you ever end up doing this? I have a N52 head going on an N54 and was curious about the rocker arms after putting in S85 springs and hardware.

[AmuroRay]

No, never had a chance. I have an N55 now.