Rocker Arm Soup..... I miss my CA (sorta)
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ImportIntelligence
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912.0turbo
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Onizuka
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Dori Dori wrote:RAS is to prevent valve float people. Rockers are still a suck *** design and can/will break from running at high rpms and/or tons of power.
Thats not their purpose. They prevent the rockers from comming off the hydraulic lash adjusters.
912.0turbo, Im sure your rocker arms broke as a result of your valves smashing into the pistons, pauls broke from excessive revs.
Honestly, this design is not as bad as people play it out to be.
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912.0turbo
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I'm pretty sure I've read somewhere that a dislodged rocker somehow cuased valve float...who knows though, I read so much stuff sometimes I confuse myself. But technically, the RAS is just to prevent the rocker from moving, hence the name. Numerous things can result after the rocker dislodges itself though...
Anyway, the only reason I said that was because some people were under the assumption that the RAS kit keeps rockers from breaking.
And yes, the design of the valve train does suck. Free floating rockers, hydraulic tappets, and a timing chain. Barf. The only other major downfall of the SR is the retarded oil pan and pickup.
Anyway, the only reason I said that was because some people were under the assumption that the RAS kit keeps rockers from breaking.
And yes, the design of the valve train does suck. Free floating rockers, hydraulic tappets, and a timing chain. Barf. The only other major downfall of the SR is the retarded oil pan and pickup.
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Onizuka
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Weak valve springs and high rpms cause valve float. The RAS sits on the opposit side of the cam from the valves, over top of the hydraulic lash adjusters.
And the valve train doesnt suck, pauls pushing over 400hp and he revved it to 8000 rpms, crap breaks when you do that to a motor. Its not the greatest design but it was cheap for nissan to make. Rocker arms breaking is not common, im much more worried about a bad water pump than my rocker arms breaking within the next 10 years.
And the valve train doesnt suck, pauls pushing over 400hp and he revved it to 8000 rpms, crap breaks when you do that to a motor. Its not the greatest design but it was cheap for nissan to make. Rocker arms breaking is not common, im much more worried about a bad water pump than my rocker arms breaking within the next 10 years.
J-Spec Tuner wrote:Weak valve springs and high rpms cause valve float. The RAS sits on the opposit side of the cam from the valves, over top of the hydraulic lash adjusters.
And the valve train doesnt suck, pauls pushing over 400hp and he revved it to 8000 rpms, crap breaks when you do that to a motor. Its not the greatest design but it was cheap for nissan to make. Rocker arms breaking is not common, im much more worried about a bad water pump than my rocker arms breaking within the next 10 years.
Damn right.
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Cyberkreig
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Here here!
Swap your water pump at the first sign of warm weather. I just did mine in a heated garage. Should have heard the old one squeel!
If someone can help clarify this for me.. Rocker arm is Y shaped. One end sits on the lashOther ends sit on the valvespring/retainer assembly.Cam strikes above the spring end. Opening the valves.
So if the rocker arm happens to break, the valves stop opening, closed by the springs, keeping them from damaging themselves & the piston.
Am i right on this? Seems like a good enough design to me?
Swap your water pump at the first sign of warm weather. I just did mine in a heated garage. Should have heard the old one squeel!
If someone can help clarify this for me.. Rocker arm is Y shaped. One end sits on the lashOther ends sit on the valvespring/retainer assembly.Cam strikes above the spring end. Opening the valves.
So if the rocker arm happens to break, the valves stop opening, closed by the springs, keeping them from damaging themselves & the piston.
Am i right on this? Seems like a good enough design to me?
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Hijacker
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J-Spec Tuner wrote:Weak valve springs and high rpms cause valve float. The RAS sits on the opposit side of the cam from the valves, over top of the hydraulic lash adjusters.
And the valve train doesnt suck, pauls pushing over 400hp and he revved it to 8000 rpms, crap breaks when you do that to a motor. Its not the greatest design but it was cheap for nissan to make. Rocker arms breaking is not common, im much more worried about a bad water pump than my rocker arms breaking within the next 10 years.
damm straight!
the only major problem with the rocker arm design is added valvetrain mass. it's not neccessarily a weak design.
Hope you all won't hate me for this but..
Sorry if I gave off the impression I didn't know what valve float was Tuner, but I do. Like I said, my memory got jumbled about the RAS and I basically typed before thinking. :\ I was just hoping to let people know that it won’t keep the rocker from breaking. Your comment about rockers rarely breaking though is funny. I barely have enough fingers to count how many times I've seen or heard of broken rockers in an SR pushing moderate power. One little miss-shift and it can be all over. Then again, most of the people I associate with are racers so the engines see much more high rpm driving and miss-shifting (amongst other things) than a street car. I definitely agree though that the rockers aren’t anything to really worry about on your average person’s street car. High powered SR's for sure. I'd like to question your comment about it being cheaper for Nissan to manufacture the engine with rockers though. In my eyes, the fact that it has more parts would make it more expensive to build. Anyway, where did you get this information from?
As for the discussion about the general design of the valve train...rockers on a ohc engine make no sense to me. One of the purposes of an ohc engine was to have less reciprocating weight (by eliminating rockers and pushrods). By putting free floating rockers on an ohc engine, IMHO, it's just another part to break that serves no obvious positive purpose. Add some hydraulic tappets and a timing chain to the mix and I see a pretty piss poor valve train. The tappets could be fixed though, unfortunately it's expensive. Don't get me wrong, the bottom end is top notch...stout as they come, the SR is a great performing engine; but they should've used a valve train design similar to the FJ, CA, RB, ect. Too bad. I'm sure I'll get flamed for this...the CA guys were ready to kill me when I voiced my opinion about the bottom end of the SR being stronger (at least in stock v stock form). I hope this can remain civil though.
It would be interesting to hear from Paul on this subject as he’s had both the CA and the SR. Which one do you feel has the better valve train design? Also, after a good amount of time with the SR, which do you like better? Last I talked w/ Rock, he said you’ve become quite fond of the SR.
Cyberkreig, maybe a pic will make things even clearer, but there is no end that sits on the valve side of the rocker. It’s more like a spring/knuckle that holds the rocker in place on the tappet side (the side it jumps off of).
As for the discussion about the general design of the valve train...rockers on a ohc engine make no sense to me. One of the purposes of an ohc engine was to have less reciprocating weight (by eliminating rockers and pushrods). By putting free floating rockers on an ohc engine, IMHO, it's just another part to break that serves no obvious positive purpose. Add some hydraulic tappets and a timing chain to the mix and I see a pretty piss poor valve train. The tappets could be fixed though, unfortunately it's expensive. Don't get me wrong, the bottom end is top notch...stout as they come, the SR is a great performing engine; but they should've used a valve train design similar to the FJ, CA, RB, ect. Too bad. I'm sure I'll get flamed for this...the CA guys were ready to kill me when I voiced my opinion about the bottom end of the SR being stronger (at least in stock v stock form). I hope this can remain civil though.
It would be interesting to hear from Paul on this subject as he’s had both the CA and the SR. Which one do you feel has the better valve train design? Also, after a good amount of time with the SR, which do you like better? Last I talked w/ Rock, he said you’ve become quite fond of the SR.
Cyberkreig, maybe a pic will make things even clearer, but there is no end that sits on the valve side of the rocker. It’s more like a spring/knuckle that holds the rocker in place on the tappet side (the side it jumps off of).
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Onizuka
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I have no problem having a discussion about this, im actually very interested in getting to the bottom of it.
When looking at the valve train from a design point of veiw, there has to be advantages and disadvatages. A multi-million dollar corperation isnt going to just throw a valvetrain thats crappy in every way posible into a motor that has been in production for over 13 years now. Catagories might be: performance, durrability, cost of manufacture and ease of assembly. If direct cam on valve is cheaper, more efficient, more durrable and easier to assemble, why would a team of profesional engineers put a rocker arm setup in a motor meant to make power and take abuse?
I already know its easy to take apart and put back together because I did it with a Kmart toolset and a torque wrench fairly quick. The rocker arms amplify the cam profiles onto the valves and allow for one cam lobe to drive 2 valves (more lobes = more expensive camshaft), thus the camshafts are made of less material as well (less reciprocating mass). I find it to be a quite innovative design, just not as durrable as high HP application users would prefer. Ill take that loss of durrablity in the valvetrain with the beefy bottom end, light weight fortified block and overbuilt transmission without complaint
When looking at the valve train from a design point of veiw, there has to be advantages and disadvatages. A multi-million dollar corperation isnt going to just throw a valvetrain thats crappy in every way posible into a motor that has been in production for over 13 years now. Catagories might be: performance, durrability, cost of manufacture and ease of assembly. If direct cam on valve is cheaper, more efficient, more durrable and easier to assemble, why would a team of profesional engineers put a rocker arm setup in a motor meant to make power and take abuse?
I already know its easy to take apart and put back together because I did it with a Kmart toolset and a torque wrench fairly quick. The rocker arms amplify the cam profiles onto the valves and allow for one cam lobe to drive 2 valves (more lobes = more expensive camshaft), thus the camshafts are made of less material as well (less reciprocating mass). I find it to be a quite innovative design, just not as durrable as high HP application users would prefer. Ill take that loss of durrablity in the valvetrain with the beefy bottom end, light weight fortified block and overbuilt transmission without complaint
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Cyberkreig
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Dori Dori - I was referring to the contact point between the RA and the valve (retainer?).
If i had to venture a guess as to the reason for the design. I would guess that Jspec is on the right track with reducing rotational mass. Lighter camshafts mean easier revs. It is a small displacement square motor afterall, quick revs are the design.
If i had to venture a guess as to the reason for the design. I would guess that Jspec is on the right track with reducing rotational mass. Lighter camshafts mean easier revs. It is a small displacement square motor afterall, quick revs are the design.
You're making assumptions at this point and the discussion to me is now basically useless. Why Nissan did what they did is beyond you and I...that’s a fact. To say they are too good/affluent of a corporation to make a mistake is a joke. I'm sure my car's super hicas is awesome too right? I mean, it must be if a multi-million dollar corporation put it there, right (considering it's more expensive, heavier, less durable, and more difficult to assemble)?
You think a rocker on a SR is innovative? You must not realize how long they've been around for. You think it's a smart way to save valve train mass too (you don’t even know if it did save weight b/c you’d have to measure up to something that never existed to know for sure)? Look no further than the current Evo's 4g63 to find out the right way to save valve train mass.
You think a rocker on a SR is innovative? You must not realize how long they've been around for. You think it's a smart way to save valve train mass too (you don’t even know if it did save weight b/c you’d have to measure up to something that never existed to know for sure)? Look no further than the current Evo's 4g63 to find out the right way to save valve train mass.