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EFI/N2O JUNKIE
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I noticed during the last race the tach in Ericas car was reading correctly on the burnout, but after that it went back down to 2000 or so and stayed there as usual. Why is that? Do the Pro Stock drivers actually watch the tach for the burnout? The switch that enables the RPM Limiter for the burnout also enables the tach?
 

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I noticed during the last race the tach in Ericas car was reading correctly on the burnout, but after that it went back down to 2000 or so and stayed there as usual. Why is that? Do the Pro Stock drivers actually watch the tach for the burnout? The switch that enables the RPM Limiter for the burnout also enables the tach?
It was discussed in the old PS thread but they switch it off after the burnout so they don't have the added distraction.
 

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Very much its application specific. The beehive and conicals we run tighter. Our typical bracket .900-.950 lift stuff we are about .080 seems to be happy. The 500 depending on the cam design and a few other factors, anywhere from .090 to .145. It also depends on the brand, some brands qc is horrible, and the information on the box about bind height can be off significantly. We crush every spring we use on every motor on our computer spring tester/dyno so we know its actual solid length. Even the sportsman stuff.

I wouldnt run my stuff that close at that rpm BTW. We are normally .080 from theoretical lift with a psi dr1248ml or dr1249ml.

Another interesting tidbit i found the hard way.
Some manufacturers over ratio the rocker to account for flex. Most everything ive seen gets back the lost flex lift with rpm, as the pole vault pole eventually straightens out...lol. So a printed rocker of 1.70 can be as much as a 1.78 actual. Ive seen this destroy a few motors, one a 632 prostock, and one other was a friends 540 blower motor. it went solid and pushed the adjuster up through the alum rocker.



this is just how we do it here. I know others do things differently, but ive had success doing it like that here.
Thank you, appreciate your comments. I do compress the springs to coil bind and measure. Never what the box claims. I think I will add some additional space in there. Thanks again.
 

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Like all have have said, it's application specific. All of the valve train affects the spring coil clearance. Ever watch a slow mo video of a spring? They sure do dance around. Do the Hula sometimes too. Almost have to do a spintron test to see if they bind in one of those dances.
 

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Like all have have said, it's application specific. All of the valve train affects the spring coil clearance. Ever watch a slow mo video of a spring? They sure do dance around. Do the Hula sometimes too. Almost have to do a spintron test to see if they bind in one of those dances.
LOL.....seems I've misplaced my Spintron....
 

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LOL.....seems I've misplaced my Spintron....

I only pull it out to answer questions that don't deserve an answer. If you are smart enough to figure it out without creating a novel on YB just do it. You don't need any fanboys to boost your ego. This is a simple fix.
 

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I'll add one other thing about trying to set up proper coil bind that I don't think was mentioned. First off, NEVER go off your cam card using whats printed as max lift based off of their calculations. Also, you really never should figure out max lift using just math. Meaning, lift times ratio minus lash... That doesn't work!

I'm not trying to say this to bash Bob with his above comment on the two failures and learning the hard way. But if you are truly trying to set up bind to a specific number those two failures would of never happened.

First off, I have never seen any rocker arm (not that I have checked them all) that has the same ratio as stamped. Most and I believe all rocker arms have more ratio than what is stamped. The extra ratio is not included to accommodate flex but is there because of motion loss due to it being exactly what it is called, a "rocker arm". Through physics a rocker arms motion is an arc which has motion loss. If you truly made an arm with a 1.7 ratio and then actually calculated out what the true ratio is, you would get less than 1.7. I believe most manufactures add a half ratio to compensate for that loss of motion. So by adding ratio when you check the arm it's now much closer to a 1.7 ratio.

The true and I feel the only way to set up coil bind is to mock up the system using all the same parts as you would when its going together for the final time. I will use shim instead of trying to crush a head gasket to make that part easier. I will put the cam in, snug down the head using shim stock to replace the head gasket and put the valve train all together. Again, using all the same parts as you would when if goes together for the final time. Meaning, I don't use "soft" springs or mock-up pushrods. Keep in mind to find max lift, you do not need to go through the process of degreeing in the cam. Unless you are also trying to figure out P2V, then you would have to. I've actually made a tool, so all I assemble is a cam, head and valve train with no crank in the block. I can just turn the cam with the tool I made. You also only have to do just one cylinder so don't mock up the entire engine to do this. You can do one side at a time which can make it easier to do. So set the valve lash accordingly and then put he dial indicator on the spring or retainer and make sure it's on a flat spot. Set zero and rotate the cam and physically see what you have for max lift is.

Then to set you installed height, now it's just math. You then take you bind height of the spring plus your gross valve lift plus your desired coil bind clearance and you have now very accurately come up with a "true" installed height for your engine. If you do it that way, you will never have a coil bind issue. The biggest variable is in the spring itself. Like mentioned above, all springs have a spec bind number. Some manufactures are pretty good being within +/- .010 which is still within tolerance. I have seem some be plus .040 which then would affect things if installed to tight. Hopefully everything above made sense and hopefully to some have a better understanding on the process...

Nick
 

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I've actually made a tool, so all I assemble is a cam, head and valve train with no crank in the block. I can just turn the cam with the tool I made.
Nick
Would you be willing to share a pic of this tool?

How do you keep the cam from spinning when the lifter goes "over the nose" and down the closing ramp? Does it have a ratcheting mechanism or one-way bearing?
 

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Nick
Im going to disagree with using the real springs for figuring max lift and ill explain why



Every single spintron trace ive seen, the valve gets back to theoretical lift when the parts "unwind" at rpm. At lower rpm not necessarily, but at higher rpm, it gets to theoretical or beyond as everything lofts and unwinds.


So if you set the springs say .100 from bind, and you had .040 deflection due to the real springs, when everything unwinds up high, you are now .060 (im just pulling numbers out of my ass for demonstration purposes)



this is why we are doing it now with a soft spring and getting the actual real lift at the valve, and the actual true ratio of the rocker, because i want to account for the "pole vault" action of the parts as they unwind. We are probably farther from bind than i think with the sportsman stuff, but its working great.



Again, this is just how i do it, and my rational behind doing it this way. YMMV, but since we have adopted this several years back things seem to be much happier out in the real world.


Carry on
 

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I'll add one other thing about trying to set up proper coil bind that I don't think was mentioned. First off, NEVER go off your cam card using whats printed as max lift based off of their calculations. Also, you really never should figure out max lift using just math. Meaning, lift times ratio minus lash... That doesn't work!

I'm not trying to say this to bash Bob with his above comment on the two failures and learning the hard way. But if you are truly trying to set up bind to a specific number those two failures would of never happened.

First off, I have never seen any rocker arm (not that I have checked them all) that has the same ratio as stamped. Most and I believe all rocker arms have more ratio than what is stamped. The extra ratio is not included to accommodate flex but is there because of motion loss due to it being exactly what it is called, a "rocker arm". Through physics a rocker arms motion is an arc which has motion loss. If you truly made an arm with a 1.7 ratio and then actually calculated out what the true ratio is, you would get less than 1.7. I believe most manufactures add a half ratio to compensate for that loss of motion. So by adding ratio when you check the arm it's now much closer to a 1.7 ratio.

The true and I feel the only way to set up coil bind is to mock up the system using all the same parts as you would when its going together for the final time. I will use shim instead of trying to crush a head gasket to make that part easier. I will put the cam in, snug down the head using shim stock to replace the head gasket and put the valve train all together. Again, using all the same parts as you would when if goes together for the final time. Meaning, I don't use "soft" springs or mock-up pushrods. Keep in mind to find max lift, you do not need to go through the process of degreeing in the cam. Unless you are also trying to figure out P2V, then you would have to. I've actually made a tool, so all I assemble is a cam, head and valve train with no crank in the block. I can just turn the cam with the tool I made. You also only have to do just one cylinder so don't mock up the entire engine to do this. You can do one side at a time which can make it easier to do. So set the valve lash accordingly and then put he dial indicator on the spring or retainer and make sure it's on a flat spot. Set zero and rotate the cam and physically see what you have for max lift is.

Then to set you installed height, now it's just math. You then take you bind height of the spring plus your gross valve lift plus your desired coil bind clearance and you have now very accurately come up with a "true" installed height for your engine. If you do it that way, you will never have a coil bind issue. The biggest variable is in the spring itself. Like mentioned above, all springs have a spec bind number. Some manufactures are pretty good being within +/- .010 which is still within tolerance. I have seem some be plus .040 which then would affect things if installed to tight. Hopefully everything above made sense and hopefully to some have a better understanding on the process...

Nick
I agree!
 

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Nick
Im going to disagree with using the real springs for figuring max lift and ill explain why



Every single spintron trace ive seen, the valve gets back to theoretical lift when the parts "unwind" at rpm. At lower rpm not necessarily, but at higher rpm, it gets to theoretical or beyond as everything lofts and unwinds.


So if you set the springs say .100 from bind, and you had .040 deflection due to the real springs, when everything unwinds up high, you are now .060 (im just pulling numbers out of my ass for demonstration purposes)



this is why we are doing it now with a soft spring and getting the actual real lift at the valve, and the actual true ratio of the rocker, because i want to account for the "pole vault" action of the parts as they unwind. We are probably farther from bind than i think with the sportsman stuff, but its working great.



Again, this is just how i do it, and my rational behind doing it this way. YMMV, but since we have adopted this several years back things seem to be much happier out in the real world.


Carry on
Sorry, I guess we can agree to disagree on this one... I myself have done hundreds of sweeps on the Spin-tron. One thing that is for sure is, you can't always predict what is going to happen and that's with testing just one combination. How in the world can you predict what is going to happen with each and every combination that is out there? There are several "what ifs" in Spin testing and to try and predict what is actually going to happen and set up for it I feel is completely asking for problems ahead. There are hundreds of combinations to test with and each will have it's very own traits. So I feel the best thing to do for most people is to stick with the basis which won't break parts and try and test from there...

Nick
 

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I also meant to say that if you have a system that seems to be working for your applications then that's great too....
 

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Nick
Im going to disagree with using the real springs for figuring max lift and ill explain why



Every single spintron trace ive seen, the valve gets back to theoretical lift when the parts "unwind" at rpm. At lower rpm not necessarily, but at higher rpm, it gets to theoretical or beyond as everything lofts and unwinds.


So if you set the springs say .100 from bind, and you had .040 deflection due to the real springs, when everything unwinds up high, you are now .060 (im just pulling numbers out of my ass for demonstration purposes)



this is why we are doing it now with a soft spring and getting the actual real lift at the valve, and the actual true ratio of the rocker, because i want to account for the "pole vault" action of the parts as they unwind. We are probably farther from bind than i think with the sportsman stuff, but its working great.



Again, this is just how i do it, and my rational behind doing it this way. YMMV, but since we have adopted this several years back things seem to be much happier out in the real world.


Carry on

Agree. We take it a step further and started spinning on our spintron at a low " 250-500 rpm " with a very very light inner spring only to have the laser trace the valve lift curve without deflection in the system affecting it. That's how we figure max lift with actual components being used. Stand installed height, push rod length, adjuster cup height, etc all change the ratio.
 

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Thank you, appreciate your comments. I do compress the springs to coil bind and measure. Never what the box claims. I think I will add some additional space in there. Thanks again.
Sorry I didn't get to respond to your pm soon enough.

I think if you're seeing that much variance in CB.... that is certainly a quality control problem. What exactly could cause the variance if the coils are the same dia spring to spring? Has to be a wire quality issue and that's not a good indicator to the rest of the spring.....

PSI Springs do not vary like that.
 

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Sorry, I guess we can agree to disagree on this one... I myself have done hundreds of sweeps on the Spin-tron. One thing that is for sure is, you can't always predict what is going to happen and that's with testing just one combination. How in the world can you predict what is going to happen with each and every combination that is out there? There are several "what ifs" in Spin testing and to try and predict what is actually going to happen and set up for it I feel is completely asking for problems ahead. There are hundreds of combinations to test with and each will have it's very own traits. So I feel the best thing to do for most people is to stick with the basis which won't break parts and try and test from there...

Nick

I haven't seen anyone mention Loft yet unless I missed it.

I haven't seen a healthy spintron trace that didn't show loft.... at least not with my stuff. I don't believe you can set up a spring without accounting for some kind of theoretical amount of loft even without spin data.

And you certainly don't want the spring to stack.......
 

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TTT



Nick
Im going to disagree with using the real springs for figuring max lift and ill explain why



Every single spintron trace ive seen, the valve gets back to theoretical lift when the parts "unwind" at rpm. At lower rpm not necessarily, but at higher rpm, it gets to theoretical or beyond as everything lofts and unwinds.


So if you set the springs say .100 from bind, and you had .040 deflection due to the real springs, when everything unwinds up high, you are now .060 (im just pulling numbers out of my ass for demonstration purposes)



this is why we are doing it now with a soft spring and getting the actual real lift at the valve, and the actual true ratio of the rocker, because i want to account for the "pole vault" action of the parts as they unwind. We are probably farther from bind than i think with the sportsman stuff, but its working great.



Again, this is just how i do it, and my rational behind doing it this way. YMMV, but since we have adopted this several years back things seem to be much happier out in the real world.


Carry on
 

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This conversation is a great example of the best of these forums. Giants of the industry discussing the hows and whys of the trade. It is fascinating to me that as hugely successful these guys are, they still have some different theories and procedures. Absolutely wonderful stuff guys. I personally can't thank you enough.
 
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