how stable is my valvetrain for 7krpm
11-18-2013, 07:49 AM
#1
how stable is my valvetrain for 7krpm so while my motor is out getting a refresh i am replacing my ls7 lifters with btr lifters. just want to get your guys opionions if my combo will hold up and be stable to 7 grand.
replacing ls7s with btr lifters
prc .675 lift springs
yella terra 1.7 rockers
trickflow pushrods
cnc 225 trickflows are on it with whatever valves trickflow puts in them(dont know the material)
cam is a custom ground 240/256 .647/.647 111lsa
this is all on a 383ls
c5r chain, ported oil pump, compstar rotator with diamond pistons
replacing ls7s with btr lifters
prc .675 lift springs
yella terra 1.7 rockers
trickflow pushrods
cnc 225 trickflows are on it with whatever valves trickflow puts in them(dont know the material)
cam is a custom ground 240/256 .647/.647 111lsa
this is all on a 383ls
c5r chain, ported oil pump, compstar rotator with diamond pistons
11-18-2013, 08:03 AM
#2
PRC have a lot of spring pressure compared to other drop in springs. This is good because of the weight of the YT rockers. However, the YT still will never RPM quite as high as a stock lifter due to that weight.
The other thing is the Trickflow pushrods are just 5/16. Put 3/8" in there. The TFS heads will fit them.
I don't know the lobes on the cam, but that will be the single most important thing to determining the stability of the valvetrain. How violent are the lobes?
The valves in the TFS heads are Ferrea stainless. They are 114g or so. Heavier than stock by a good bit.
All in all, you have a lot of heavy components, potentially an aggressive cam, and small diameter pushrods. Will it spin to 7K? Probably. Is it the most stable valvetrain? No.
Replacing the Ferrea valves with hollow-stem, turned-down LS3 valves would save you about 30g in weight ~84g at 2.055". Adding powdered metal guides and running stock rockers would help a lot. Adding the 3/8" pushrod would be fine. And getting a cam with lobes designed for high RPM stability would be beneficial. Then swapping to a short-travel lifter would complete the package. You could probably see well over 7500 with that setup with no valve float issues.
The other thing is the Trickflow pushrods are just 5/16. Put 3/8" in there. The TFS heads will fit them.
I don't know the lobes on the cam, but that will be the single most important thing to determining the stability of the valvetrain. How violent are the lobes?
The valves in the TFS heads are Ferrea stainless. They are 114g or so. Heavier than stock by a good bit.
All in all, you have a lot of heavy components, potentially an aggressive cam, and small diameter pushrods. Will it spin to 7K? Probably. Is it the most stable valvetrain? No.
Replacing the Ferrea valves with hollow-stem, turned-down LS3 valves would save you about 30g in weight ~84g at 2.055". Adding powdered metal guides and running stock rockers would help a lot. Adding the 3/8" pushrod would be fine. And getting a cam with lobes designed for high RPM stability would be beneficial. Then swapping to a short-travel lifter would complete the package. You could probably see well over 7500 with that setup with no valve float issues.
11-18-2013, 08:07 AM
#3
PRC have a lot of spring pressure compared to other drop in springs. This is good because of the weight of the YT rockers. However, the YT still will never RPM quite as high as a stock lifter due to that weight.
The other thing is the Trickflow pushrods are just 5/16. Put 3/8" in there. The TFS heads will fit them.
I don't know the lobes on the cam, but that will be the single most important thing to determining the stability of the valvetrain. How violent are the lobes?
The valves in the TFS heads are Ferrea stainless. They are 114g or so. Heavier than stock by a good bit.
All in all, you have a lot of heavy components, potentially an aggressive cam, and small diameter pushrods. Will it spin to 7K? Probably. Is it the most stable valvetrain? No.
Replacing the Ferrea valves with hollow-stem, turned-down LS3 valves would save you about 30g in weight ~84g at 2.055". Adding powdered metal guides and running stock rockers would help a lot. Adding the 3/8" pushrod would be fine. And getting a cam with lobes designed for high RPM stability would be beneficial. Then swapping to a short-travel lifter would complete the package. You could probably see well over 7500 with that setup with no valve float issues.
The other thing is the Trickflow pushrods are just 5/16. Put 3/8" in there. The TFS heads will fit them.
I don't know the lobes on the cam, but that will be the single most important thing to determining the stability of the valvetrain. How violent are the lobes?
The valves in the TFS heads are Ferrea stainless. They are 114g or so. Heavier than stock by a good bit.
All in all, you have a lot of heavy components, potentially an aggressive cam, and small diameter pushrods. Will it spin to 7K? Probably. Is it the most stable valvetrain? No.
Replacing the Ferrea valves with hollow-stem, turned-down LS3 valves would save you about 30g in weight ~84g at 2.055". Adding powdered metal guides and running stock rockers would help a lot. Adding the 3/8" pushrod would be fine. And getting a cam with lobes designed for high RPM stability would be beneficial. Then swapping to a short-travel lifter would complete the package. You could probably see well over 7500 with that setup with no valve float issues.
11-18-2013, 08:09 AM
#4
EPS lobes will do fine then. I'd seriously look at the rockers and pushrods. If you have the EHT springs, they'll work okay with the stock rockers, but you don't need quite as much open pressure with those (which the EHT have). I also see .647" lift... is that at 1.7? If so, the stock rockers might not be the absolute best option since they seem to scrub the valve at more than .630" lift.
If you already have the TFS heads and the YT rockers, just go to a bigger pushrod. That will help a lot.
If you already have the TFS heads and the YT rockers, just go to a bigger pushrod. That will help a lot.
11-18-2013, 08:15 AM
#5
EPS lobes will do fine then. I'd seriously look at the rockers and pushrods. If you have the EHT springs, they'll work okay with the stock rockers, but you don't need quite as much open pressure with those (which the EHT have). I also see .647" lift... is that at 1.7? If so, the stock rockers might not be the absolute best option since they seem to scrub the valve at more than .630" lift.
If you already have the TFS heads and the YT rockers, just go to a bigger pushrod. That will help a lot.
If you already have the TFS heads and the YT rockers, just go to a bigger pushrod. That will help a lot.
so im thinking the btr lifters, 3/8 pushrods, keep the rockers then how would that do if i change to the btr springs and get the hollow stem ls3s? would the rockers throw it off since thats the heaviest. or just get the pushrods and call it a day.
11-18-2013, 08:25 AM
#6
If you can get the LS3 valves and the pushrods, do that. Keep everything else the same.
The bigger, stiffer pushrod deflects much less. When a pushrod deflects, it acts as a secondary spring, absorbing some of the lift action from the cam before it is transmitted to the valve and can actually try to vault off the lifter, allowing it to loft and come off the cam before everything crashes back together once the pushrod recoils back into place. That's why you have to keep adding more and more spring pressure to keep that from occuring. The problem is your lifter has to be able to withstand that increase.
The lighter valve will help offset the weight of the rocker arm as well and help with that too.
I don't think 7K would be a problem with the LS3 valves and 3/8" pushrods.
The bigger, stiffer pushrod deflects much less. When a pushrod deflects, it acts as a secondary spring, absorbing some of the lift action from the cam before it is transmitted to the valve and can actually try to vault off the lifter, allowing it to loft and come off the cam before everything crashes back together once the pushrod recoils back into place. That's why you have to keep adding more and more spring pressure to keep that from occuring. The problem is your lifter has to be able to withstand that increase.
The lighter valve will help offset the weight of the rocker arm as well and help with that too.
I don't think 7K would be a problem with the LS3 valves and 3/8" pushrods.
11-18-2013, 08:36 AM
#7
If you can get the LS3 valves and the pushrods, do that. Keep everything else the same.
The bigger, stiffer pushrod deflects much less. When a pushrod deflects, it acts as a secondary spring, absorbing some of the lift action from the cam before it is transmitted to the valve and can actually try to vault off the lifter, allowing it to loft and come off the cam before everything crashes back together once the pushrod recoils back into place. That's why you have to keep adding more and more spring pressure to keep that from occuring. The problem is your lifter has to be able to withstand that increase.
The lighter valve will help offset the weight of the rocker arm as well and help with that too.
I don't think 7K would be a problem with the LS3 valves and 3/8" pushrods.
The bigger, stiffer pushrod deflects much less. When a pushrod deflects, it acts as a secondary spring, absorbing some of the lift action from the cam before it is transmitted to the valve and can actually try to vault off the lifter, allowing it to loft and come off the cam before everything crashes back together once the pushrod recoils back into place. That's why you have to keep adding more and more spring pressure to keep that from occuring. The problem is your lifter has to be able to withstand that increase.
The lighter valve will help offset the weight of the rocker arm as well and help with that too.
I don't think 7K would be a problem with the LS3 valves and 3/8" pushrods.
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11-18-2013, 08:42 AM
#8
That's what I did.
I went stock heads to save headaches from geometry issues, went LS3 valves, big stiff pushrods, stock rockers with upgraded trunions, good valvesprings shimmed for more seat pressure, EPS lobes, and short-travel lifters (which act more like a solid roller at higher RPM). Even though my valve events aren't crazy big, I'm hoping I can wind it up to 7400-7500.
I went stock heads to save headaches from geometry issues, went LS3 valves, big stiff pushrods, stock rockers with upgraded trunions, good valvesprings shimmed for more seat pressure, EPS lobes, and short-travel lifters (which act more like a solid roller at higher RPM). Even though my valve events aren't crazy big, I'm hoping I can wind it up to 7400-7500.
11-29-2013, 04:38 PM
#9
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That's what I did.
I went stock heads to save headaches from geometry issues, went LS3 valves, big stiff pushrods, stock rockers with upgraded trunions, good valvesprings shimmed for more seat pressure, EPS lobes, and short-travel lifters (which act more like a solid roller at higher RPM). Even though my valve events aren't crazy big, I'm hoping I can wind it up to 7400-7500.
I went stock heads to save headaches from geometry issues, went LS3 valves, big stiff pushrods, stock rockers with upgraded trunions, good valvesprings shimmed for more seat pressure, EPS lobes, and short-travel lifters (which act more like a solid roller at higher RPM). Even though my valve events aren't crazy big, I'm hoping I can wind it up to 7400-7500.