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motorsci

Playing with fire

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Drilling holes in things certainly removes some weight but in the case of rockers you are also removing strength, if those bend or break it could destroy the valve train, some pistons and maybe the cam. Hard to believe the Nissan engineers just threw more weight on the rockers for the hell of it.

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23 hours ago, motorsci said:

This is a old rocker Iam lightening has any one else done this ? It's 10 grams lighter it's not a finished product I just started 

 

I did something more like this:

rockers.thumb.jpg.5e077619092d0696dd5713726e956558.jpg

Edited by TimZ

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17 hours ago, Chickenman said:

^ That looks a lot safer than drilling holes and creasting stress risers. You're actually removing stress risers by polishing. Not that I've ever seen a stock Nissan rocker break in two. The " Forge " be strong with these. 

Yeah I had some time on my hands while the block was at the machine shop :mrgreen:

I'd be a bit leery about drilling holes too - these rockers also weighed significantly less (don't remember the amount offhand - it was several years ago) and have had no issues whatsoever.  To Chickenman's point, I also paid a lot of attention to details like eliminating potential stress risers, trying to get the direction of grinding/polishing aligned down the length of the part, and spent a lot of time polishing them.  Those took me roughly 8 hours each to complete.

Edited by TimZ

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23 hours ago, grannyknot said:

Drilling holes in things certainly removes some weight but in the case of rockers you are also removing strength, if those bend or break it could destroy the valve train, some pistons and maybe the cam. Hard to believe the Nissan engineers just threw more weight on the rockers for the hell of it.

 

It's not really for the hell of it but for manufacturability, i.e. at some point you're adding steps and time to your process for diminishing returns. They can be further optimized for specific applications, as Tim has done. Doesn't mean that the Nissan engineers purposely threw more weight on them, nor does it mean that Tim necessarily knows something the engineers didn't. It's all a matter of application.

 

I also don't see a great case for a broken rocker destroying pistons or the valvetrian. You can nick a cam lobe maybe. E30s break rockers on track all the time, swap the offending rocker and off you go.

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5 hours ago, grannyknot said:

and how much weight did you manage to take off them?

As i said it was several years ago and I don't remember the exact amount.  There was a significant amount of material removed, though.  

 

I went and found the thread where we were discussing this at the time and it appears it was on the order of 3 grams/rocker:

 

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it's all a nice exercise...
Have titanium valves, retainers, spring keepers? Well then lighten that reciprocating end and run a lighter spring, you might be good to 24,000 rpms!

stock nissan rockers on our bonneville engine were stable to 13,000 rpms in our testing. I think valve, spring, and cam profile selection play a much more critical role.

If you note the E-Motive guys polished theirs similar to TimZ. We didn't even do that, though I have in the past on other engines (Yamaha....)

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Thank you all for your input I have titanium retainers locks and DSI valves from Datsun spirt I have a good unmolested. Set of rockers to put in but just enjoying a little time off work and waiting for the machine shop have a press with a tension gauge and was going to make a fixture to measure the deflection at the tip and what it takes to break it compared to a stock rocker here is a pic it ready to polish 66 grams 

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95B96A87-A92B-4E92-996D-359BA290362E.jpeg

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I read the topic That dragon fly started maybe iam simple but my plan was to measure the before and after valve train weight and figure the difference as a % then subtract that from the valve spring tension and order springs 

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I read the topic That dragon fly started maybe iam simple but my plan was to measure the before and after valve train weight and figure the difference as a % then subtract that from the valve spring tension and order springs 

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