Which valve springs?
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 1,132
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Which valve springs?
I bought fast burn heads fully assembled - these come with the LT4-ZZ4 valve springs. I also bought the crane camponents kit / melonized distributor gear to do a retro hydraulic roller setup for my LT4 hotcam. The crane camponents kit came with dual springs. Should I swap the valve springs just for good measure, or am I okay running the ZZ4 springs? I have a TH-400 transmission with stock gears (stock for a 71) and I'll be running 1.6 roller rockers.
GM # 12551483 Valve Spring "LT4-ZZ4"
This single valve spring is use on 1996 LT4 Production Corvettes and ZZ4 crate engines.
Technical Notes: Single spring with 1.32" O.D. and 1.22" solid height. The pressure at installed height IS 101# @ 1.78" with 332# the average rate of pounds per inch.
# 270-99838-16 Crane Dual Valve Springs
Outer Spring, Outer Diameter: 1.465''
Outer Spring, Inner Diameter: 1.091''
Inner Spring, Inner Diameter: .807''
Damper: NO
Seat Pressure @ Installed Height: 110# @ 1.688''
Open Pressure and Height: 320# @ 1.208''
Coil Bind: .950''
Average Spring Rate: 438 #/IN
GM # 12551483 Valve Spring "LT4-ZZ4"
This single valve spring is use on 1996 LT4 Production Corvettes and ZZ4 crate engines.
Technical Notes: Single spring with 1.32" O.D. and 1.22" solid height. The pressure at installed height IS 101# @ 1.78" with 332# the average rate of pounds per inch.
# 270-99838-16 Crane Dual Valve Springs
Outer Spring, Outer Diameter: 1.465''
Outer Spring, Inner Diameter: 1.091''
Inner Spring, Inner Diameter: .807''
Damper: NO
Seat Pressure @ Installed Height: 110# @ 1.688''
Open Pressure and Height: 320# @ 1.208''
Coil Bind: .950''
Average Spring Rate: 438 #/IN
Last edited by majic1984; Jan 13, 2006 at 11:21 AM.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Run the springs that came with the cam, no brainer. You have to set the springs up correctly too, regarding installed height etc. Othe complications might arise if the heads are not machined for double spring diameter 
Last edited by MotorHead; Jan 14, 2006 at 01:06 PM.
Burning Brakes
Joined: Aug 2002
Posts: 1,146
Likes: 10
From: Scottsboro Alabama
The Lt4 springs will work fine with the hot cam, .525 lift w/ 1.6 rockers. Leave your assembled heads as they are. The Crane springs wont work with the fast burns unless you machine out the spring pockets. If you ever decide to upgrade the hot cam to a higher lift cam you will need to change the lt4 springs. Comp Cams makes a beehive spring .625 lift that is a direct drop in replacement for the fast burns (no machine work). I dont see a need for you to keep the Crane springs. 
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 1,132
Likes: 0
Thanks guys for all your responses. I was in the garage all day today stripping my engine - I learned a good bit about it since it was a non-original motor that had been put there by the previous owner (however, for some reason, he had no idea what his builder had done to it). I did have one very good surprise when I pulled the heads tonight... the cylinders are punched out 60 over and it looks to have been rebuilt less than 1000 miles ago. 
