rocker geometry - check all valves?
07-01-2013, 05:25 PM
#1
rocker geometry - check all valves? Hey all,
I'm planning a heads/cam swap with yella terra rockers later this year. I understand the theory behind shimming the rockers and also checking the wipe pattern.
Right now I have fully assembled heads. Should I just put the heads on and use a solid lifter to check/adjust the wipe pattern? I would rather not have to take the dual springs off if I don't have to.
Also, do you guys check every cylinder, or just check one cylinder and set the shim heights all the same? I'm only asking because taking heads on and off 8 times would really suck, but if that's the only "proper" way to do it, I will do so.
Thanks!
I'm planning a heads/cam swap with yella terra rockers later this year. I understand the theory behind shimming the rockers and also checking the wipe pattern.
Right now I have fully assembled heads. Should I just put the heads on and use a solid lifter to check/adjust the wipe pattern? I would rather not have to take the dual springs off if I don't have to.
Also, do you guys check every cylinder, or just check one cylinder and set the shim heights all the same? I'm only asking because taking heads on and off 8 times would really suck, but if that's the only "proper" way to do it, I will do so.
Thanks!
07-01-2013, 10:04 PM
#2
No need to keep taking the heads on and off, this can be done on your bench. If you have checker springs you don't need the cam, lifters, or pushrods to do this. Just so you know - setting the wipe pattern should be done BEFORE you measure for pushrod length / check PTV.
Install checker springs and coat the valve tip with dychem, hi-spot marking fluid, sharpie, etc. Then install the rocker and snug it up. Compress the spring by hand and move the rocker through full travel several times, then remove the rocker and observe the contact patch. Too close to the intake - needs less shim. Too close to the exhaust, needs more shim. Ideally your contact patch is narrow and centered. I think Vettenuts was able to get his set to 0.045" wide or so.
In the YT instructions, it says to set all rockers up the same once you've established what you need to achieve your wiper pattern. The exception to this is if you have heads with some hand work / rework done to them - anything that would cause variation in valve seat depth. If that isn't the case though, I would follow their recommendations and set them all up the same.
Vettenuts had a write up about this, check this out: http://forums.corvetteforum.com/1563994999-post1.html
hope that helps.
Install checker springs and coat the valve tip with dychem, hi-spot marking fluid, sharpie, etc. Then install the rocker and snug it up. Compress the spring by hand and move the rocker through full travel several times, then remove the rocker and observe the contact patch. Too close to the intake - needs less shim. Too close to the exhaust, needs more shim. Ideally your contact patch is narrow and centered. I think Vettenuts was able to get his set to 0.045" wide or so.
In the YT instructions, it says to set all rockers up the same once you've established what you need to achieve your wiper pattern. The exception to this is if you have heads with some hand work / rework done to them - anything that would cause variation in valve seat depth. If that isn't the case though, I would follow their recommendations and set them all up the same.
Vettenuts had a write up about this, check this out: http://forums.corvetteforum.com/1563994999-post1.html
hope that helps.
Last edited by ckpitt55; 07-01-2013 at 10:10 PM.
07-01-2013, 11:02 PM
#4
You could always check for peace of mind, but I doubt it would be more than a few thou difference if any if it was a CNC deal.
Yes, you'll need to remove the dual springs and install lightweight checker springs in their place - you wouldn't be able to manipulate them by hand otherwise (unless you have really really strong hands lol). You can get them from jegs, goodson, etc. These are the ones I have (set of 8).. http://www.goodson.com/VTS-8_-Heavy-...cking_Springs/. Much cheaper than the ones sold at Jegs btw.
-Chuck
Yes, you'll need to remove the dual springs and install lightweight checker springs in their place - you wouldn't be able to manipulate them by hand otherwise (unless you have really really strong hands lol). You can get them from jegs, goodson, etc. These are the ones I have (set of 8).. http://www.goodson.com/VTS-8_-Heavy-...cking_Springs/. Much cheaper than the ones sold at Jegs btw.
-Chuck
07-02-2013, 07:09 AM
#6
OP. If the heads are off I would check a few because the valves have been worked just to ensure they are the same heights. Since you are using YT's, and they install in pairs, if you find the intake and exhaust require different shim heights you may need to compromise because you need to use the same shim under the pair and not put different shims under each side of the rocker pair. Also, if the valves are set deeper, you may not need shims but actually may need to cut the rocker stands to lower the rockers depending on how deep they were set in compared to stock since the YT rockers are designed for stock heights. This isn't to say they won't work, but something to be aware of as you start your project. If the heads are off, as stated above, this work is more easily done on the work bench just make sure to set the heads on some 2X4's or something to allow the valves to open to your cam's lift on the cylinder you are working on.
07-02-2013, 07:12 AM
#7
It is actually the opposite. If too close to the intake side of the valve stem the rocker is raised to push the tip outward and vice versa.
OP. If the heads are off I would check a few because the valves have been worked just to ensure they are the same heights. Since you are using YT's, and they install in pairs, if you find the intake and exhaust require different shim heights you may need to compromise because you need to use the same shim under the pair and not put different shims under each side of the rocker pair. Also, if the valves are set deeper, you may not need shims but actually may need to cut the rocker stands to lower the rockers depending on how deep they were set in compared to stock since the YT rockers are designed for stock heights. This isn't to say they won't work, but something to be aware of as you start your project. If the heads are off, as stated above, this work is more easily done on the work bench just make sure to set the heads on some 2X4's or something to allow the valves to open to your cam's lift on the cylinder you are working on.
OP. If the heads are off I would check a few because the valves have been worked just to ensure they are the same heights. Since you are using YT's, and they install in pairs, if you find the intake and exhaust require different shim heights you may need to compromise because you need to use the same shim under the pair and not put different shims under each side of the rocker pair. Also, if the valves are set deeper, you may not need shims but actually may need to cut the rocker stands to lower the rockers depending on how deep they were set in compared to stock since the YT rockers are designed for stock heights. This isn't to say they won't work, but something to be aware of as you start your project. If the heads are off, as stated above, this work is more easily done on the work bench just make sure to set the heads on some 2X4's or something to allow the valves to open to your cam's lift on the cylinder you are working on.
