rocker arms...

[Purple pit]

Oh wow that is way off. I was getting crazy thoughts about buying some, but not now.

[3400-95-Modified]

Well hot damn... anyone want some 3.9L rockers... LOL

[geldartb]

Well hot damn... anyone want some 3.9L rockers... LOL

lol i was ready to hit the buy it now the other day on the set you bought.. was waiting to see how this thread panned out before i bought them even at $35.

could always make wall decorations out of them or christmas ornaments. lol

[ericjon262]

bummer, thanks for the picture ben.

[Xnke]

I know, long dead thread, but why not just reshape the tip of the rocker for proper geometry...it's not like it hasn't been done before. They're investment cast steel rockers, it would not be hard at all to reshape and re-harden if they weren't through-hardened to start.

I am looking at fitting LS1 1.7 ratio rocker arms to the intake of my engine, just to get the extra bit of lift-I'm not running over 0.500" lift, but the way the cam lift and duration numbers came out I'd like to get a 1.7 ratio rocker onto the intake side of things.

[34blazer]

I know, long dead thread, but why not just reshape the tip of the rocker for proper geometry...it's not like it hasn't been done before. They're investment cast steel rockers, it would not be hard at all to reshape and re-harden if they weren't through-hardened to start.

I am looking at fitting LS1 1.7 ratio rocker arms to the intake of my engine, just to get the extra bit of lift-I'm not running over 0.500" lift, but the way the cam lift and duration numbers came out I'd like to get a 1.7 ratio rocker onto the intake side of things.

The What- Reshaping Rocker tips for better geometry

The How- ?????

[ericjon262]

sure you could reshape the tip, but in doing so you'll probably reduce the ratio. and is there really any gain from using a different rocker?

[Xnke]

The ratio is set by the distance from the contact pad on to the rocker shaft, and the rocker shaft to the pushrod cup. Reshaping the end isn't going to change the ratio, unless you move the entire contact pad left or right.

The advantage is getting to use the 1.7 ratio on an intake coupled with a 1.6 on the exhaust. My build doesn't call for a lot of duration, but to make best use of the cylinder heads I need to get that intake valve kicked up near 0.500" lift. The cam profile I settled on only pushes it to 0.440 with a 1.5 ratio, 0.460 with the stock 1.6, and with the 1.7 ratio (If I can make it work) it would be 0.498...which would be absolutely usable. By using rocker ratio to my advantage I can get my flat-tappet cam profile to approximate the hydraulic roller profile that I would like to run. Doing a hydraulic roller conversion just isn't in the cards on this build, so I'll take my lift anyway I can get it.

Also, it may be that the rocker doesn't need reshaped at all, it may be that the rocker pedestal is just too tall. That's easy enough to fix.

[Guest]

The advantage is getting to use the 1.7 ratio on an intake coupled with a 1.6 on the exhaust. My build doesn't call for a lot of duration, but to make best use of the cylinder heads I need to get that intake valve kicked up near 0.500" lift. The cam profile I settled on only pushes it to 0.440 with a 1.5 ratio, 0.460 with the stock 1.6, and with the 1.7 ratio (If I can make it work) it would be 0.498...which would be absolutely usable. By using rocker ratio to my advantage I can get my flat-tappet cam profile to approximate the hydraulic roller profile that I would like to run. Doing a hydraulic roller conversion just isn't in the cards on this build, so I'll take my lift anyway I can get it.

why not just get a different cam with more lift? these specs are with 1.5 ratio

http://www.summitracing.com/parts/crn-253941/overview/

[ericjon262]

The ratio is set by the distance from the contact pad on to the rocker shaft, and the rocker shaft to the pushrod cup. Reshaping the end isn't going to change the ratio, unless you move the entire contact pad left or right.

The advantage is getting to use the 1.7 ratio on an intake coupled with a 1.6 on the exhaust. My build doesn't call for a lot of duration, but to make best use of the cylinder heads I need to get that intake valve kicked up near 0.500" lift. The cam profile I settled on only pushes it to 0.440 with a 1.5 ratio, 0.460 with the stock 1.6, and with the 1.7 ratio (If I can make it work) it would be 0.498...which would be absolutely usable. By using rocker ratio to my advantage I can get my flat-tappet cam profile to approximate the hydraulic roller profile that I would like to run. Doing a hydraulic roller conversion just isn't in the cards on this build, so I'll take my lift anyway I can get it.

Also, it may be that the rocker doesn't need reshaped at all, it may be that the rocker pedestal is just too tall. That's easy enough to fix.

I understand how a rocker works, have you looked at the picture ben posted on the last page? the geometry is way off, if you're able to reshape the tip to make the geometry work without reducing the ratio, I would be moderately impressed.

[34blazer]

Shortening the pedestals may be an option for those willing to experiment.

Sent from my XT1080 using Tapatalk

[ericjon262]

Shortening the pedestals may be an option for those willing to experiment.

Sent from my XT1080 using Tapatalk

why shorten them, shorter pedestals already exist, the 3900 uses a taller pedestal (or shorter, I don't remember...) than the 3x00. the 3800 and LSx also use a very similar rocker that probably has it's own height as well.

[34blazer]

Well then...

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[ericjon262]

found some pics from another thread...

Whoops, haven't posted/ looked at this whole thread in ages...

[Xnke]

I understand how a rocker works, have you looked at the picture ben posted on the last page? the geometry is way off, if you're able to reshape the tip to make the geometry work without reducing the ratio, I would be moderately impressed.

The shape of the tip is wrong, it that's why it's pushing on the valve edge. That kind of problem is the reason why roller-tip rocker arms were invented to start with.

I've designed rocker arms from scratch before, so reshaping one isn't a big deal. Just a matter of having enough material or working within the limits of the material you already have. The ones I made were in an OHC application so they're a bit different, but valve geometry is valve geometry-if it's wrong, fix it, if it's right, it's right.

As for getting a cam with more lift...

If I retain the same 1.6 rockers I've already got, then adding any more lift is going to add more duration. I do not need or want more duration. Adding duration is what pushes a car from fun to drive every day but makes decent horsepower, to miserable to drive every day but makes a ton of horsepower. I'm also working with a flat tappet cam, which when coupled with the chevy 0.842" lifter diameter puts hard limits on ramp rates. By leveraging the rocker ratio, I can get roller-cam ramp rates at the valve tip, while retaining flat-tappet ramp rates at the lifter interface. Can be hell on valve springs if you take this method too far, though.

The pedestal height is the easy method here, but existing pedestals may or may not have a solution. "Bolt-on" doesn't mean shit to me, if I have to make custom pedestals, that's an afternoon's work, once I have the valve geometry the way I want it.


Um...those are Your photos from THIS thread....