Lunati Spring recommendations
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Joined: Feb 2012
Posts: 419
Likes: 4
From: Long Beach, MS
Lunati Spring recommendations I'm feeling a little confused by spring specs. Lunati recommends spring kit 73943 for just about all their LT1 camshafts.
On the cam cards is states "installed height 1.750 = 108lbs", which seems a little low for load on the seat for a hydraulic roller, from what I've read.
Then when you actually look at the specs for the spring it reads:
Product Description
Type: Single With Damper
O.D. Outer: 1.260"
I.D. Outer: .876"
I.D. Inner: N/A
Coil Bind: 1.028"
Seat Load: 98 @ 1.750"
Open Load: 330 @ 1.250"
Rate (lbs/in): 462
Quantity: 1
Part Number: 73943-1
98lbs seat pressure for a hydraulic roller with an rpm range of 2800-6400rpm and .565 lift?
Am I missing something here, or is this just way off?
Wouldn't this be letting the valve bounce well before 6400rpm?
Just looking for some insight here. Trying to learn a bit about spring requirements and they just kinda have thrown me for a loop with their recommendations.
Thanks
On the cam cards is states "installed height 1.750 = 108lbs", which seems a little low for load on the seat for a hydraulic roller, from what I've read.
Then when you actually look at the specs for the spring it reads:
Product Description
Type: Single With Damper
O.D. Outer: 1.260"
I.D. Outer: .876"
I.D. Inner: N/A
Coil Bind: 1.028"
Seat Load: 98 @ 1.750"
Open Load: 330 @ 1.250"
Rate (lbs/in): 462
Quantity: 1
Part Number: 73943-1
98lbs seat pressure for a hydraulic roller with an rpm range of 2800-6400rpm and .565 lift?
Am I missing something here, or is this just way off?
Wouldn't this be letting the valve bounce well before 6400rpm?
Just looking for some insight here. Trying to learn a bit about spring requirements and they just kinda have thrown me for a loop with their recommendations.
Thanks
I'm feeling a little confused by spring specs. Lunati recommends spring kit 73943 for just about all their LT1 camshafts.
On the cam cards is states "installed height 1.750 = 108lbs", which seems a little low for load on the seat for a hydraulic roller, from what I've read.
Then when you actually look at the specs for the spring it reads:
Product Description
Type: Single With Damper
O.D. Outer: 1.260"
I.D. Outer: .876"
I.D. Inner: N/A
Coil Bind: 1.028"
Seat Load: 98 @ 1.750"
Open Load: 330 @ 1.250"
Rate (lbs/in): 462
Quantity: 1
Part Number: 73943-1
98lbs seat pressure for a hydraulic roller with an rpm range of 2800-6400rpm and .565 lift?
Am I missing something here, or is this just way off?
Wouldn't this be letting the valve bounce well before 6400rpm?
Just looking for some insight here. Trying to learn a bit about spring requirements and they just kinda have thrown me for a loop with their recommendations.
Thanks
On the cam cards is states "installed height 1.750 = 108lbs", which seems a little low for load on the seat for a hydraulic roller, from what I've read.
Then when you actually look at the specs for the spring it reads:
Product Description
Type: Single With Damper
O.D. Outer: 1.260"
I.D. Outer: .876"
I.D. Inner: N/A
Coil Bind: 1.028"
Seat Load: 98 @ 1.750"
Open Load: 330 @ 1.250"
Rate (lbs/in): 462
Quantity: 1
Part Number: 73943-1
98lbs seat pressure for a hydraulic roller with an rpm range of 2800-6400rpm and .565 lift?
Am I missing something here, or is this just way off?
Wouldn't this be letting the valve bounce well before 6400rpm?
Just looking for some insight here. Trying to learn a bit about spring requirements and they just kinda have thrown me for a loop with their recommendations.
Thanks
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
I'm currently installing that spring kit; 73925K5. Make sure you check the installed height. I came in at 1.710". I ordered Comp cams spring locators, 4682-16. They come in Friday. I'll let you know how they fit if you need.
If you get +.050" locks, you need to make sure they fit the retainer correctly. Crower makes some that fit very nice, but you can't run self aligning rockers with them depending on the valves you have.]
UPDATE: The locators fit perfectly! P/N: CCA-4682-16
If you get +.050" locks, you need to make sure they fit the retainer correctly. Crower makes some that fit very nice, but you can't run self aligning rockers with them depending on the valves you have.]
UPDATE: The locators fit perfectly! P/N: CCA-4682-16
Last edited by hrcslam; Mar 5, 2016 at 11:03 AM.
I would not use the 73943 kit. 100lbs is nowhere near enough, especially with steel retainers and heavy LT1 valves. Even the 10308-1 kit sets up around 130.
160lbs on the seat sounds like a lot. I am only running 170 on the seat in my engine which will ultimately see 10psi from a blower (recommended specs by Lloyd). Lobes are 226/239 .565/.587. My AFR valves are much bigger than stock but weigh roughly the same.
I have a set of LE1s with the Lunati 73925K5 springs on them. A combination of those springs, aggressive lobes (LE grind similar to XFI 467 with a little more lift), and too much pressure for tired 120k stock lifters caused an oiling issue up top resulting in grooved stock valve tips. Locators from the kit were used. Maybe the installed height was too short (like 1.710" mentioned above) and that's what caused the wear?
160lbs on the seat sounds like a lot. I am only running 170 on the seat in my engine which will ultimately see 10psi from a blower (recommended specs by Lloyd). Lobes are 226/239 .565/.587. My AFR valves are much bigger than stock but weigh roughly the same.
I have a set of LE1s with the Lunati 73925K5 springs on them. A combination of those springs, aggressive lobes (LE grind similar to XFI 467 with a little more lift), and too much pressure for tired 120k stock lifters caused an oiling issue up top resulting in grooved stock valve tips. Locators from the kit were used. Maybe the installed height was too short (like 1.710" mentioned above) and that's what caused the wear?
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
LLoyd was the one who specked the Lunati springs for my XFI cam and said to set them up at 1.780. He said seat 155-160 and open was 380. Since my heads have previously had the spring pockets machined down for springs installed at 1.800" I had no problem setting them up at 1.780using .020 shims under the locators.
Catmaigne, if you didn't confirm installed height, how do you know how much open & seat pressure you have? If they were like 1.71x than yeah you would have more seat than the 155-160 I have
Stock heads like hrcslam has give 1.71x to 1.75x" in installed spring height so yeah a shorter installed height will increase seat & open pressure...and in some cases that is to much for a particular cam and can tax lifters
I got 20k mi out of Comp 918's before one broke (or whenever it did break during the 20k mi) but fortunately I had no engine damage as a result. That spring break was under the retainer so the retainer held the spring together, fortunately.
Catmaigne, if you didn't confirm installed height, how do you know how much open & seat pressure you have? If they were like 1.71x than yeah you would have more seat than the 155-160 I have
Stock heads like hrcslam has give 1.71x to 1.75x" in installed spring height so yeah a shorter installed height will increase seat & open pressure...and in some cases that is to much for a particular cam and can tax lifters
I got 20k mi out of Comp 918's before one broke (or whenever it did break during the 20k mi) but fortunately I had no engine damage as a result. That spring break was under the retainer so the retainer held the spring together, fortunately.
I bought the LE1s used for my Roadmaster knowing all of the valves needed to be replaced. I didn't bother checking the installed height on the Lunati duals because I'm not reusing them, they are total overkill for the wimpy cam that'll be going in. Car gets the crap beat out of it and will be an occasional tow rig so I didn't want something aggressive.
