Good sense or waste of $ to change springs on stock LS6 motor getting ATI D1SC SC
08-09-2005, 04:39 PM
#1
TECH Fanatic
Thread Starter
iTrader: (1)
Join Date: Oct 2002
Location: Elmhurst, IL (Chicago Suburb)
Posts: 1,851
Likes: 0
Received 0 Likes
on
0 Posts
Good sense or waste of $ to change springs on stock LS6 motor getting ATI D1SC SC My bolt on 02 Z (with 20K miles on stock motor) is soon going to be blown by a D1SC Procharger Kit. For durability, liability, and piece of mind, even though my LS6 motor itself will remain stock (no cam change) and i will not spin higher than 6500 rpms, does it make sense to make a valve spring change to something like Patriot dual golds with titanium retainers or is this is a waste of time and $ and should i just stick with the stock LS6 already on the car!! 
THANKS for you helpful insight and experience :thumbs:
PS-If you recommend a spring change which dual makes most sense and has similar seat pressure to stock LS6 single behive, that will not cause too much pressure and may cause other unforseen issues? I know 918s but i spend the time and $ to swap out springs i am going with duals for piece of mind of not dropping a valve, etc.
THANKS for you helpful insight and experience :thumbs:
PS-If you recommend a spring change which dual makes most sense and has similar seat pressure to stock LS6 single behive, that will not cause too much pressure and may cause other unforseen issues? I know 918s but i spend the time and $ to swap out springs i am going with duals for piece of mind of not dropping a valve, etc.
08-09-2005, 06:16 PM
#3
10 Second Club
iTrader: (3)
Join Date: Mar 2004
Location: orlando, fl
Posts: 4,266
Likes: 0
Received 0 Likes
on
0 Posts
here's what vinci says about spring choices when going supercharger.
http://www.vincihighperformance.com/...20PAGE%20.HTML and of course, buy the vinci/crane duals. i use them on the wife's car with stock cam. drop in, no modifications to the head needed.
http://www.vincihighperformance.com/...20PAGE%20.HTML and of course, buy the vinci/crane duals. i use them on the wife's car with stock cam. drop in, no modifications to the head needed.
Originally Posted by VHP tech and tuning page
Is Choosing The Right Valve Springs for Supercharged Engines Critical?
Selecting the proper valve spring for any performance engine is important; but it is critical to proper operation of supercharged engines. Consider the fact that when the engine is in a "boosted" condition, the supercharger (or turbocharger) is trying to blow the intake valve open. The boost pressure actually reduces the intake valve spring seat pressure. This is extremely critical on engines with hydraulic lash adjustment. Proper seat pressure (working through the rocker arm and pushrod) is necessary to keep the hydraulic lifter plunger centered in the lifter body to prevent "pump-up." If an engine has 2.25" dia. intake valves, there is 4 sq. inches of backside valve area. Now add 12 (psi) of boost pressure, and you have reduced your effective seat pressure by 48 lbs. (12 lbs/sq.in. X 4 sq. in.). If you started out with 120 lbs. of seat pressure (static), you now have 72 lbs. of operational seat pressure. There is no way that 72 lbs. of pressure is going to control a 2.25" valve!
Selecting the proper valve spring for any performance engine is important; but it is critical to proper operation of supercharged engines. Consider the fact that when the engine is in a "boosted" condition, the supercharger (or turbocharger) is trying to blow the intake valve open. The boost pressure actually reduces the intake valve spring seat pressure. This is extremely critical on engines with hydraulic lash adjustment. Proper seat pressure (working through the rocker arm and pushrod) is necessary to keep the hydraulic lifter plunger centered in the lifter body to prevent "pump-up." If an engine has 2.25" dia. intake valves, there is 4 sq. inches of backside valve area. Now add 12 (psi) of boost pressure, and you have reduced your effective seat pressure by 48 lbs. (12 lbs/sq.in. X 4 sq. in.). If you started out with 120 lbs. of seat pressure (static), you now have 72 lbs. of operational seat pressure. There is no way that 72 lbs. of pressure is going to control a 2.25" valve!
08-10-2005, 01:21 AM
#5
TECH Senior Member
iTrader: (18)
Join Date: Jun 2002
Location: NW Houston, TX
Posts: 10,036
Likes: 0
Received 0 Likes
on
0 Posts
I agree, I would deff change them. With any type of forced induction the back of the valve sees a lot of presure from the extra air (dont know if I worded that right) but ive seen blower cars stop making power at 4k because the valve springs werent up to the task. A 918 would do you just fine. A dual seems to be a bit over kill, but I dont see how it would hurt.
08-10-2005, 02:32 AM
#6
TECH Senior Member
It all depends on how much boost you run, the more boost, the stiffer the spring should be.
if you're running in the 7psi neighbourhood then 918's would be good uprade, more than that and a set of 921 Comp will do the trick, or Crane duals.
if you're running in the 7psi neighbourhood then 918's would be good uprade, more than that and a set of 921 Comp will do the trick, or Crane duals.
08-10-2005, 03:54 AM
#7
I have been corresponding with the originator of this thread on another forum. I just want to bounce my opinion off of some of the knowledgable people who have responded here. If I were in this situation, I would be concerned about increasing the spring loads too high since the original timing chain is still in place. For that reason, I would lean towards the Crane duals since the seat pressure is a little lower and the spring is not quite as stiff as the 918's. In my research, the timing chain failures I found were those where spring pressures were increased a lot, and for reliability purposes I would try to steer towards lower spring loads.
Comments/thoughts?
Comments/thoughts?
Trending Topics
08-10-2005, 03:59 AM
#8
TECH Senior Member
iTrader: (18)
Join Date: Jun 2002
Location: NW Houston, TX
Posts: 10,036
Likes: 0
Received 0 Likes
on
0 Posts
I forgot about the crane springs. I agree though. You do need a better spring, but not as much as some of the dual springs will give you. I assumed your still running stock compression so I fig your not gona run a lot of boost, and thats why I suggested a spring that wasnt so heavy duty.
08-10-2005, 05:48 PM
#9
10 Second Club
iTrader: (3)
Join Date: Mar 2004
Location: orlando, fl
Posts: 4,266
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by vettenuts
I have been corresponding with the originator of this thread on another forum. I just want to bounce my opinion off of some of the knowledgable people who have responded here. If I were in this situation, I would be concerned about increasing the spring loads too high since the original timing chain is still in place. For that reason, I would lean towards the Crane duals since the seat pressure is a little lower and the spring is not quite as stiff as the 918's. In my research, the timing chain failures I found were those where spring pressures were increased a lot, and for reliability purposes I would try to steer towards lower spring loads.
Comments/thoughts?
Comments/thoughts?
