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pushrods and rockers

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    Senior Member steele211's Avatar
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    Default pushrods and rockers

    Are an .080 wall 3/8 pushrod and crower ss stud mount rocker with a stud girdle up to the task of a .799 lift cam and 800# of open pressure to 8k? Also what is the Rex axle upgrade in the morel lifters. Are they going to work in this same setup?

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    gn7
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    Quote Originally Posted by steele211 View Post
    Are an .080 wall 3/8 pushrod and crower ss stud mount rocker with a stud girdle up to the task of a .799 lift cam and 800# of open pressure to 8k? Also what is the Rex axle upgrade in the morel lifters. Are they going to work in this same setup?
    NO!
    Not even close.
    .120 aren't even up to the job but a far cry better.
    You really need 7/16 X .120

    The ONLY reason for not using 7/16 PRs is cost. There is not other reason. None.



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    Last edited by gn7; 03-31-2013 at 10:49 AM.

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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by gn7 View Post
    NO!
    Not even close.
    .120 aren't even up to the job but a far cry better.
    You really need 7/16 X .120

    The ONLY reason for not using 7/16 PRs is cost. There is not other reason. None.
    I've used the 3/8 .080 wall push rods with TD rockers with a 780 lift cam at 7800 350 lbs on seat and 780 lbs open ,. I guess I was lucky for a couple of years. Since then I cut back on the camshaft lift, I did have to stay on top of the valve adjustment after every day of raceing. now I don't have to. not that much power loss either.
    Last edited by jimclauss; 03-31-2013 at 02:54 PM.

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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by steele211 View Post
    Are an .080 wall 3/8 pushrod and crower ss stud mount rocker with a stud girdle up to the task of a .799 lift cam and 800# of open pressure to 8k? Also what is the Rex axle upgrade in the morel lifters. Are they going to work in this same setup?
    Right or wrong, I've used 3/8" .080 wall push rods, girdles and quality stud mount rockers in most of my drag race type applications up to around .800" lift and 8200 RPM. I do pay pretty close attention to making sure the geometry is as close to perfect as I can get it and check valve train pretty regularly. Works for me....
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

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    Quote Originally Posted by steele211 View Post
    Are an .080 wall 3/8 pushrod and crower ss stud mount rocker with a stud girdle up to the task of a .799 lift cam and 800# of open pressure to 8k? Also what is the Rex axle upgrade in the morel lifters. Are they going to work in this same setup?
    You can get a lesson by calling Manton or Smith Brothers and see what they recommend. Both have lots of years of experience and practical testing. I bet you a nickel both will suggest heavier wall 7/16"

    If you go to 7/16",, might want to mock up heads to verify clearance before doing final assembly, since they may require some grinding.

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    Living in a cage of fear thatguy's Avatar
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    Is there a point where pushrod weight/ momentum becomes a problem when running 7/16 pushrods?

    just wondering as I have heard some engine guys talk about it.
    Tommy
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    gn7
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    We've all done it. Doesn't make it right.
    In think there may have been a reason GM put 7/16 PRs in the L88, ZL1 and LS7s for a reason, and I am gusessing they did it based on testing, not on a hunch.
    Like Barry said, one call to Manton, Smiths or Trend will get you the same answer I gave. Been there, done that.

    Will 3/8 X .080 will work. So will a cast crank, 3/8 rods and TRW pistons. We/ve all done it.

    My point is, if you qant to run big rollers, you should treat the PRs EXACTLY the same way would the springs. Nobody thinks twice going against the RECOMMENDED spring pressure, put the PR gets kicked to the curb to save pennys.

    I have no problem with the rockers and studs. No my personal choice, but I understand using them.

    Amybody want to suggest stock sled ball to save a couple bucks?. Then why not larger PRs. The price diff is much less than stock rockers VS decend rollers.

    The pricew diff on Manton's 3/8 X .080 and a 7/16 X 120 is less than $1.50 per PR. There has to be a better place to save 25.00 on a roller engine build.



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    Last edited by gn7; 03-31-2013 at 04:34 PM.

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    Just because a pushrod doesn't break doesn't mean it's right. A pushrod isn't supposed to be a secondary spring in the valve train, but that's exactly what one becomes when it's too small for the app. Suddenly you find yourself running 800# springs when 600# springs should do the job. Ideally, a pushrod needs to be as rigid as possibel with no flex, and not introduce any secondary dynamic input into the valve train.
    Bottom line is, you really can't put too big of a pushrod in an engine that's running a .700"+ SR with some spring pressure and moderate rpm. The weight on that side of the rocker is far less relevant than the benefit of the bigger pushrod. Also remember, you get more rigidity with cross sectional diameter than you do wall thickness.
    On 7/16 pushrids with stud mount rockers...you'll have to run a straight wall hardened pushrod compatable with guide plates. This can cause clearance issues, and there are only two sources for 7/16 guide plates that I'm aware of: GM, and Comp Cams. The Comp guide plates will probably have to be cut, aligned and re-welded. Converting a stud rocker BBC over to 7/16 pushrods is definitely worth while, but it's a job.
    Last edited by scott foxwell; 03-31-2013 at 04:32 PM.
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    Quote Originally Posted by thatguy View Post
    Is there a point where pushrod weight/ momentum becomes a problem when running 7/16 pushrods?

    just wondering as I have heard some engine guys talk about it.
    Short answer: no.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    gn7
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    Quote Originally Posted by steelcomp View Post
    This can cause clearance issues, and there are only two sources for 7/16 guide plates that I'm aware of: GM, and Comp Cams. The Comp guide plates will probably have to be cut, aligned and re-welded. Converting a stud rocker BBC over to 7/16 pushrods is definitely worth while, but it's a job.
    Manley sells 7/16 giuge plates as well.



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    steelcomp was here
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    Quote Originally Posted by gn7 View Post
    Manley sells 7/16 giuge plates as well.
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    gn7
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    If the effort to make 7/16 work is more than you want to take on, then 3/8 X .120 is the minimum I would consider. Like Steel said, the ridgity comes from the diameter cross , but .120 is still a major improvement over .080.



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    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by steelcomp View Post
    Just because a pushrod doesn't break doesn't mean it's right. A pushrod isn't supposed to be a secondary spring in the valve train, but that's exactly what one becomes when it's too small for the app. Suddenly you find yourself running 800# springs when 600# springs should do the job. Ideally, a pushrod needs to be as rigid as possibel with no flex, and not introduce any secondary dynamic input into the valve train.
    Bottom line is, you really can't put too big of a pushrod in an engine that's running a .700"+ SR with some spring pressure and moderate rpm. The weight on that side of the rocker is far less relevant than the benefit of the bigger pushrod. Also remember, you get more rigidity with cross sectional diameter than you do wall thickness.
    On 7/16 pushrids with stud mount rockers...you'll have to run a straight wall hardened pushrod compatable with guide plates. This can cause clearance issues, and there are only two sources for 7/16 guide plates that I'm aware of: GM, and Comp Cams. The Comp guide plates will probably have to be cut, aligned and re-welded. Converting a stud rocker BBC over to 7/16 pushrods is definitely worth while, but it's a job.
    Quote Originally Posted by steelcomp View Post
    Short answer: no.

    Thanks Scott.

    Many years ago as a machinist in race engine shops I would see some customers and engine builders go with big PR's then add all kinds of rev kits and spring pressure to compensate, while others would scoff at the big push rods. Still others would run the big pushrods and scoff at the rev kits.
    Back then there seemed to be very distinct lines in the sand between the different theories.
    I never had anything myself that required all that, and kind of always wondered what the actual truth was.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

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    gn7
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    Quote Originally Posted by thatguy View Post
    Thanks Scott.

    Many years ago as a machinist in race engine shops I would see some customers and engine builders go with big PR's then add all kinds of rev kits and spring pressure to compensate, while others would scoff at the big push rods. Still others would run the big pushrods and scoff at the rev kits.
    Back then there seemed to be very distinct lines in the sand between the different theories.
    I never had anything myself that required all that, and kind of always wondered what the actual truth was.
    Everything on the pushrod side of the rocker fulcrum has almost no effect on the springs ability to control the valve. In fact the springs size and its own wieght plays a much larger part in the valve trains stability. The springs own weight is counter productive. The benefits of a stiffer pushrod far exceed any down side to the additional wieght of the larger PR.

    Go on Ebay and look at the size of the PRs sold by the NASCAR teams and keep in mind they are running considerably shorter PRs, that by their length are already stiffer. And they are turning 10.000 rpm and no rev kits. Think they are testing this stuff on Spintrons?
    Bet there isn't a single NHRA Pro Stock running a 3/8 PR of any wall thickness. Doubt there are too many holding the diameter to 7/16. 1/2 X 7/16 taper is probably more like it.



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    Last edited by gn7; 04-01-2013 at 04:09 PM.

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