Valve Spring Coil Bind Question for Injuneer, Wolfman

[jbs4radio]

Hey guys,

I'm trying to research the valve spring coil bind specs onthe valve springs GM P/N 12551483 that come in the LT4 hot cam kit. The cam itself with 1.6 roller rockers gives a .525 lift on intake and exhaust. The only info I can find is the 101# @ 1.78" with 332 the average rate of pounds. Nothing mentioned about the coil bind? Sallee Chevrolet's parts department gave me a .539 but nothing in writing. What's you advice, knowledge about them?

Jared

[bn_bullet]

Jared,

The LT-4 valve spring, Part number 12551483 (1 ea.) has a listed solid height of 1.22" and an installed height of 1.78" @101#. This means that there is .560" from installed height to solid height. The LT-4 Hotcam achieves .525" max lift with the 1.6 rocker so I would say that is about as much lift as I would trust these springs to. This only allows 0.035" before reaching coil bind and I really wouldn't push these springs any more than that. Hope this helped.

Brian

p.s. You can also find this spring under part number 12495494. It is the same spring just 16 each of the 12551483 part number.

[wolfdogs]

i kept my ol spec sheet on the cam and kit.. ill see if i can dig it up. brians answer seems to do it though.

[jbs4radio]

Thanks for the advice guys. I'd appreciate a copy of that spec sheet if you find it Wolfman. The guy that's putting my heads back together at Motorworks said something about needing .090 . I do not know quite enough yet about it. I just figured I'd take the 1.78 and subtract the amount of lift .525 and pray there was more than 1.22 left over. I'm confused as to if it is 1 and 7/8 inch or 1.78 inches. The difference being 1.875 and 1.78 of course. The math I did comes up to the same as Brian .035 for the 1.78. A little more for the 1.875 leaves .13 What's the standard clearance that is recommended?

Jared

[bn_bullet]

Jared,

The Lt-4 spring is indeed listed as 1.78" (not 1.875"). IMO, the max lift should be no less than .050" from coil bind. Of course, the Hotcam already violates this as it only leaves .035". I cannot dispute the LT-4 springs success when used with the Hotcam but I wouldn't want to push the spring any harder. I believe that GM maxed out the capabilities of these springs when they chose them for the Hotcam kit. I speculate that they were primarily limited by the small valve spring pockets on the LT-1 and LT-4 cylinder heads and chose the spring to fit.

You may want to ask your machine shop if they have a Rimac spring tester (or equivalent) and see if they can check your springs. This would be the best way to ensure the integrity of your valvetrain. Just my 2 cents...

Brian