LT4 spring help (install height)
04-06-2007, 04:32 PM
#1
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Location: Commerce, MI
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LT4 spring help (install height)
I just talked to my head guy and he said with the LT4 springs on the LT1 head he gets an installed height of 1.78 without the shims! and the shims are forty thousandths. He is worried that with the shims the installed spring pressure will be to high for the hotcam. With the shims the installed height will be between 1.745 and 1.73. Will this be okay? the pressure may be around 110-125. thanks
04-06-2007, 05:59 PM
#2
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Location: Saginaw, Michigan
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They are designed for the Hotcam with 1.6 RR's on stock heads. You are using the seats and retainers that go with the LT4 springs right? If so, you are all set.
The hotcam is .525" lift with 1.6 RR's.
Dan
The hotcam is .525" lift with 1.6 RR's.
Dan
04-06-2007, 07:48 PM
#3
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And the LT4 springs are too weak for the HOT cam, they work marginally well with the LT4's lighter valves though but that doesn't help you does it?
I would recommend gettung better springs before going any further. Those LT4 springs are prefect for a stock cam/1.6 rocker setup.
I would recommend gettung better springs before going any further. Those LT4 springs are prefect for a stock cam/1.6 rocker setup.
04-07-2007, 12:03 PM
#4
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And the LT4 springs are too weak for the HOT cam, they work marginally well with the LT4's lighter valves though but that doesn't help you does it?
I would recommend gettung better springs before going any further. Those LT4 springs are prefect for a stock cam/1.6 rocker setup.
I would recommend gettung better springs before going any further. Those LT4 springs are prefect for a stock cam/1.6 rocker setup.
Dan
04-07-2007, 12:59 PM
#5
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Valvefloat is much more common that people realize, I am basing my comments on reality rather than what "should" work.
04-07-2007, 08:39 PM
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Dan
04-07-2007, 09:39 PM
#9
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I agree with both of you but, why take a chance on a so-so spring? As 96 said, the LT4 had lighter valves. And who knows how long those springs will be efficient once they go through many heat cycles? I'd like to see some dyno charts of the same car with new springs (Hotcam) and then one with maybe 10k on them. Like I said, why take a chance, and or, have to do the springs again down the road?
04-09-2007, 08:07 PM
#13
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I agree, the LT4 springs are junk...based on many engine dyno runs.
Your machinist needs to familiarize himself with roller cam spring pressures, if anything, those pressures are too low for a performance application. I do at minimum 125# seat and 295# open. Make sure he checks for distance to coil bind after max lift too.
You should get this information at minimum when a set of heads are built:
Valve sizing
Guide clearance
Spring installed height
Seated pressure
Open pressure
Distance to coil bind
Retainer to seal clearance
Your machinist needs to familiarize himself with roller cam spring pressures, if anything, those pressures are too low for a performance application. I do at minimum 125# seat and 295# open. Make sure he checks for distance to coil bind after max lift too.
You should get this information at minimum when a set of heads are built:
Valve sizing
Guide clearance
Spring installed height
Seated pressure
Open pressure
Distance to coil bind
Retainer to seal clearance
Last edited by MachinistOne; 04-09-2007 at 08:09 PM.
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