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1995 Cadillac Fleetwood Brougham
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Discussion Starter #1
I am looking for information on the LT4 valve springs, specifically with regard to our iron heads.

On more than one occasion, I have read that the LT4 springs do not fit our heads without machining. However, I have a friend who has been running these springs for several years with no apparent issues. What gives?

Also, what are the installed pressure and max lift for the LT4 springs?

Thanks,

Matt
 

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The issue with using LT4 springs on iron heads is the valves are not hollow sodium filled valves like LT4 thus the LT1 solid valves are heavier so new LT4 springs are not really any improvement. Crane 10309-1 are for iron heads. What I put on

The LT4 springs otherwise "fit" and cheap but not a good upgrade let alone as good as new stock iron head valve springs
 

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Discussion Starter #4
At 132#, doesn't that make them significantly beefier than both the stock springs and the Edelbrock 5703's? Or is that not how it works?
 

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do you have a camshaft in mind?
pressures with the edelbrocks; 110# @ 1.7 and 285# @ .490 lift
 

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Discussion Starter #6
I'm not planning to use the LT4 springs, I'm just trying to clarify for academic reasons.

I'm confused because everything that I've read about the LT4 springs is that they either don't work or aren't an upgrade. Meanwhile, I consistently hear good things about the Edelbrock springs as a budget option for our cars. How can this be if the LT4 springs are 132# and the Edelbrock springs are 110#?
 

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Discussion Starter #8

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FWIW, I would not use the LT4 spring at an install height of 1.70"
+1 on dunno if O.D. is a problem.
 

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I was looking at cams last year, talked to somebody at comp about valve springs for a 07-500-8.
I was told that the 981-16 springs would not work but that the 26918 beehives (1.31" od) were a drop in on iron heads.....
Also, accd. to their own web site the 981-16 is ok for the 08-408-8 cam but not the 07-500-8. These are the same lobes ground on different centers...
 

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The OD is the problem. They do not fit in the seat (my experience). I attempted to use on a 1.6 rocker only upgrade (which is their best use IMO on an aluminum head). I had Howards 98215’s ready to go and used those without the dampener for fitment.
 

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Discussion Starter #12
My friend sent me these pictures just now. Are the springs supposed to all be slightly off center like that?
 

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Here are stock LT1 springs and retainers:
F394D0D7-E557-48BD-A37A-E17CBB4F071C.jpeg DB60EC32-A857-4BC1-9EA6-6129975ED5B3.jpeg

Here are LT4 springs and LT4 retainers:
955BC813-64F2-4758-9093-FB14E31A19E1.jpeg FF8AD7F2-5A0A-4E51-84F3-F94A8ACBD9D9.jpeg C7137D14-3118-4A42-9059-CB7F7C8B8BD3.jpeg

Sorry these are sideways...

While the pics of his (and mine IMO) retainer fit looks off, that appears to be the way it is. I know mine fit fine and no concern when it went together. I weighed retainers and were identical in weight to stock. They appeared the same in fit as well but were only ~$20 so no loss.

I guess I should add if the springs are not sitting in the seat right on his heads (I have aluminum heads) that could be an issue but have no experience putting something like that together as it was a no-go for me.
 

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I will concede it may be an illusion because the tapered end is making the spring look offset.
As long the retainer step is close or tight fitting to the inside of the spring, then the actual spring is centered even though the ground end makes it look offset.
Sorry for being an alarmist.
 

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It doesn’t look right to me either... That and the larger OD of an LT4 spring in an iron head caught my attention- I pulled a VC and took the pics because I was alarmed at what I saw! 😂
I tried LT4 springs on an iron head when I had my wagon and was no bueno for me. I was a little surprised how my aluminum head set-up looked as well, probably not quite as off as they appear in the pics though.
 

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Discussion Starter #18
Okay, so...

The diameter of the LT4 springs is slightly greater than the diameter of the spring seats on the iron heads. How big of an issue is this? Could a person argue that the springs still locate and function just fine, or is this a definite problem?
 

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I don’t think it would be something most in the know would try. It’s possibly close enough in a stock application to live but could create premature wear. As long as a valve doesn’t drop, you’d think there would eventually be signs of issues (possibly around guide or seat wear) resulting in oil consumption or some performance degradation/gradual loss of compression. All speculation on my part but thats why getting the right springs are cheap insurance and peace of mind. Just my $.02c...
 

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they might work with .050 offset retainers (1.75" install) on a mild cam but unless one had a set sitting around I wouldn't even try. + $0.02

cheaper to use the edelbrock 'z28' springs and stock retainers. Tested mine recently, after 10k miles (stock B cam) they checked out at 105-108# @ 1.7 and (IIRC) around 270# at .460 lift.
 
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