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post #33 of (permalink) Old 09-10-2005, 11:57 AM
Join Date: Aug 2005
Posts: 3,943
Q: What should I look for when upgrading my valvetrain?


- For any cam swap you MUST change out valve springs. The stock springs are only good enough for the stock cam and barely at that.

- As far as springs go you have a few but not limited to the following choices:

1. Comp 918?s: A few years back they had some problems with non-blue stripe springs breaking but they have seemed to rectified the problem. The beehive design is also a superior setup. Your stock steel retainers can be reused with the 918?s but titanium retainers are recommended for lightening up the valvetrain and for strength.

Outside Diameter (O.D.): 1.290"/1.060"
Inside Diameter (I.D.): .885"/.656"
Installed Pressure: 130 lbs @ 1.800"
Open Pressure: 318 lbs @ 1.200''
Coil Bind: 1.085"
Maximum Lift: 0.625"
Rate (lbs/in): 313 lbs/in

2. Manley Nextek: Also a single spring like the 918?s but not of the beehive variety. They are a good spring and come in a package deal from SDPC for 178 and that includes titanium retainers. The springs are rated for up to .600 lift.

Max Valve Lift : .600"
O.D. : 1.255"
I.D. : .830
Installed Pressure : [email protected]"
Open Pressure : [email protected]"
Coil Bind : 1.100"

3. Crane Duals: A dual spring setup rated for up to .650 lift. When buying duals you?ll need the dual springs (obviously), titanium retainers, new dual spring seats, and new valve stem seals.

The installed seat pressure is 112 lbs @ 1.800'' with a maximum recommended lift of .650'' at the valve with an accompanying open pressure of 352 lbs. The 1.275'' O.D.

112lbs @ 1.800
352lbs @ 1.150
will handle .650 lift with .045 coil clearance


4. Comp 921?s: Also a dual spring like the Cranes above and come as a kit with everything you need for installation, rated for up to .650 lift

O.D: 1.300
I.D: .870 (outer spring)
I.D: .655 (inner spring)
135 LBS @ 1.770
400 LBS @ 1.220
COIL BIND @ 1.040

5. Patriot Gold Duals: See Crane and 921?s. The PP Golds are currently the best direct drop in spring, they are the stand set for the new AFR heads and come on all PP heads. PP are the only genIII spring setup to use the super 7 locks.

O.D 1.29
135lbs @ 1.800
385lbs open
coil bind @ 1.08
.650 lift

jrp's Personal Indepedently tested PP golds:

seat: 143 lbs @ 1.800
open: 363 @ 1.200
coil bind: 1.060
Clearance: .140
spring rate: 367

6. PRC Dual Spring Kit: Kit comes with Dual springs, tit. retainers (using stock locks), seats, valve stem seals. good for up to .660 lift

seat : 140lbs
open: 390lbs
install : 1.800
coil bind: 1.07
1.290 O.D.
max lift : .660
matl : super pure chrome silicone

Comp 977's: dual spring (requires machining of spring pockets)

O.D: 1.46
I.D: .700
seat pressure: 155 @ 1.850
open presure: 419 @ 1.250
coil bind: 1.195
spring rate: 441

Comp 978's: Dual springs (requires machining of spring pockets)

O.D: 1.46
I.D: .697
seat pressure: 126 @ 1.850
open presure: 368 @ 1.250
coil bind: 1.195
spring rate: 403

Comp 987's: Dual Springs (require maching of spring pockets)

O.D: 1.430
I.D: .697
seat pressure: 121 @ 1.800
open presure: 388 @ 1.200
coil bind: 1.150
spring rate: 344


What they are:

What they do: transfer the motion of the cam to the rockers

What to look for:

- New pushrods aren?t absolutely necessary but they are highly recommended.

- The pushrod was never designed to be a fusible link in the valvetrain. Several years ago we even had a member (might have been in the old days) that was an engineer from Jesel (don't recall his ID) and he was adamantly opposed to the notion that the LS1 pushrods were designed to break in the event of a mechanical over-rev. The job of the pushrod is to accurately transmit the motion of the cam lobe (via the rocker arm) to the valve. If it?s flexing under load, then its simply not doing its job.

Look at it this way; you CAN mechanically over-rev any engine - pushrod, OHC, rotary, or otherwise - and cause damage. There is nothing unique or special about the LS1 pushrods making them fusible.

This is like saying that you broke your ring gear on a missed shift so therefore everybody should continue using the weak 10-bolt rear ends. Just a silly, backwards argument IMO - especially when you're considered an aggressive cam with heavier valve springs (Fulton 1)
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