what height do you set your gt40 valve springs to - Ford Mustang Forums : Corral.net Mustang Forum

 
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post #1 of 9 Old 09-11-2011, 03:02 PM Thread Starter
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Lightbulb what height do you set your gt40 valve springs to

So I have gt40 heads and new valve spring kit from Alex Parts that I want to install. I have been reading a lot about install height, coil bind, and all sort.

I have stock cam with 1.72 rockers so my lift will be around .477

The springs install height @ 1.78 is 120lbs
----------------coil bind @ 1.100
----------------max lift @ .600

So if I install it at 1.78 with my .477 lift I will have .203 before coil bind...

I have the hardened shim kit so am I going to want to bring the install height down to 1.7-1.71 to be closer to .130 before coil bind

or

bring the intall height down more to be closer to .60 range... I have read multiple posts and threads and each one says something different so I would like to get an opinion on here.

I plan on going turbo with these heads in the future so I want to get this right the first time.

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post #2 of 9 Old 09-12-2011, 07:49 AM
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worry more about open and closed pressures, when you get the proper closed pressure on the seat then what ever intalled height it took to get that, so be it...and it may fall within what spec says, but you must check that and have proper stuff to do such, after that coil bind can be checked ,ect ect , knowing the cam to be used is important as well.

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post #3 of 9 Old 09-12-2011, 09:34 AM
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what is spring rate.

2007 BMW 335i
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post #4 of 9 Old 09-13-2011, 01:25 PM Thread Starter
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Its a 120lbs at 1.78" for the seat pressure.
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post #5 of 9 Old 09-13-2011, 01:40 PM
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Quote:
Originally Posted by dirty2003 View Post
Its a 120lbs at 1.78" for the seat pressure.
Spring rate?
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post #6 of 9 Old 09-13-2011, 10:21 PM Thread Starter
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sorry about that here are all the specs i have for the springs.

Spring Specifications:

•1.460" Outside Diameter

•.980" Inside Diameter

•120 Lbs @ 1.780" Valve Closed Installed Height

•280 Lbs @ .500" Lift
•310 Lbs @ .600" Lift
•No spring seat machining required
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post #7 of 9 Old 09-14-2011, 09:39 AM
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Here is what I would do.. Some one please check my math....

coil bind-----1.100
Lift----------0.477
clearance----0.123
----------------------
Installed height 1.700

At 1.700 145lbs (seat)

At 1.223 297lbs (at lift)

320lb rate.
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post #8 of 9 Old 09-15-2011, 11:56 PM Thread Starter
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Bump.... that sounds about right. Anybody else have some input
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post #9 of 9 Old 09-16-2011, 05:10 AM
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You dead set on those springs? The open rates on those Alex springs looks pretty weak, considering stock springs are at 230lbs open..i think the stock rate is like 315lbs/in if my math is correct...i wouldnt run those...i would run from those...

ive been using:
Crane 44308-1
adv. specs:
118Lbs @ 1.950
Coil bind- 1.320"
Open- 375lbs @ 1.380"
457 lb/in rate

Install @ 1.880" will put you .083" from coil bind
~150 on the seat and ~370 at lift

1987 Notch - N/A stock 302, TFS heads, Holley Systemax, FTI cam, Astro A5
Best so far: 10.92 @ 123mph with a 1.49 60ft

Last edited by tripleblackvert; 09-16-2011 at 08:13 AM.
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