What type of rocker arms do we have...
Thread Starter
Registered User
Joined: Feb 2001
Posts: 3,068
From: Cincinnati, Ohio
What type of rocker arms do we have...
I was looking at some Comp stuff, specifically the hi-tech 1.65 and 1.7 roller rockers.
Found 7/16th stud, NSA, for SBC.
Says "Not for late model rail type rockers"
What in the world is that? Basically i want to know if they are going to work on an lt1.
Found 7/16th stud, NSA, for SBC.
Says "Not for late model rail type rockers"
What in the world is that? Basically i want to know if they are going to work on an lt1.
Registered User
Joined: Feb 2004
Posts: 123
From: Houston, TX
The stock LT1 rockers are stamped steel, 1:5 ratio, 3/8" stud, self aligning.
For stock valve cover use with 1:6 roller rockers, which is the rocker you really want, you will need "Narrow" bodied rockers. Otherwise, you will need aftermarket valve covers, or need to modify the stock ones.
For stock valve cover use with 1:6 roller rockers, which is the rocker you really want, you will need "Narrow" bodied rockers. Otherwise, you will need aftermarket valve covers, or need to modify the stock ones.
Thread Starter
Registered User
Joined: Feb 2001
Posts: 3,068
From: Cincinnati, Ohio
I already have the 1.6 pro mags, NSA, with the bigger 7/16 studs.
My question was more...do we have the "late model rail type rocker" which will not work with the comp hi-tech larger ratio rockers.
My question was more...do we have the "late model rail type rocker" which will not work with the comp hi-tech larger ratio rockers.
Registered User
Joined: Oct 2003
Posts: 2,140
From: DOVER DE
Our heads use the rail type rockers. You can use non-rail typr rockers but you would have to install hardened pushrods and guide plates. To use your rockers you would also have to install 7/16 studs and possibly new valve covers. Be careful, as you can't install just any centerbolt valve cover. The LT1 uses a special RH valve cover with a recessed area to clear the alternator.
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Joined: Jan 2004
Posts: 1,406
From: Downey, CA
I'm not sure what "rail type" means. I always thought
that our options were SA and NSA, where the latter
require hardened pushrods and guideplates. I would
use a Comp Pro Magnum 1.6:1 NSA for 7/16" studs as
a guide and measure it up. Then compare to the specs
of the other rockers.
Or to better answer your question. I have no idea.
that our options were SA and NSA, where the latter
require hardened pushrods and guideplates. I would
use a Comp Pro Magnum 1.6:1 NSA for 7/16" studs as
a guide and measure it up. Then compare to the specs
of the other rockers.
Or to better answer your question. I have no idea.
Last edited by truedualws6; Mar 3, 2004 at 07:38 AM.
Registered User
Joined: Apr 2002
Posts: 465
From: AL
RE and C got it right, the rail type means self aligning.
Rail-type rocker arm with loose fit pushrod hole
289 engines built after mid-1966 and 302 engines use a rail-type rocker arm. These rocker arms have ears that extend downward, forming a rail or channel over the valve stem. This rail maintains proper alignment. The pushrod passes through a loose tolerance hole in the cylinder head, resulting in a cheaper assembly. At high RPM, however, these rockers can jump the track, loosing alignment with the valve stem and resulting in potentially serious engine damage. These engines do not require hardened pushrods. This scheme was fully adjustable until 1970 when the studs were changed to incorporate a positive stop. The rocker arm nut is no longer used to adjust the valve clearance. Rather it is simply tightened down. Longer or shorter pushrods are selected to adjust the clearance. Since these are non-adjustable they can not be used with mechanical cams.
Rail-type rocker arm with loose fit pushrod hole
289 engines built after mid-1966 and 302 engines use a rail-type rocker arm. These rocker arms have ears that extend downward, forming a rail or channel over the valve stem. This rail maintains proper alignment. The pushrod passes through a loose tolerance hole in the cylinder head, resulting in a cheaper assembly. At high RPM, however, these rockers can jump the track, loosing alignment with the valve stem and resulting in potentially serious engine damage. These engines do not require hardened pushrods. This scheme was fully adjustable until 1970 when the studs were changed to incorporate a positive stop. The rocker arm nut is no longer used to adjust the valve clearance. Rather it is simply tightened down. Longer or shorter pushrods are selected to adjust the clearance. Since these are non-adjustable they can not be used with mechanical cams.
Registered User
Joined: Dec 1969
Posts: 27,727
From: Little Rock, AR
Originally posted by Transamdriver
RE and C got it right, the rail type means self aligning.
Rail-type rocker arm with loose fit pushrod hole
289 engines built after mid-1966 and 302 engines use a rail-type rocker arm. These rocker arms have ears that extend downward, forming a rail or channel over the valve stem. This rail maintains proper alignment. The pushrod passes through a loose tolerance hole in the cylinder head, resulting in a cheaper assembly. At high RPM, however, these rockers can jump the track, loosing alignment with the valve stem and resulting in potentially serious engine damage. These engines do not require hardened pushrods. This scheme was fully adjustable until 1970 when the studs were changed to incorporate a positive stop. The rocker arm nut is no longer used to adjust the valve clearance. Rather it is simply tightened down. Longer or shorter pushrods are selected to adjust the clearance. Since these are non-adjustable they can not be used with mechanical cams.
RE and C got it right, the rail type means self aligning.
Rail-type rocker arm with loose fit pushrod hole
289 engines built after mid-1966 and 302 engines use a rail-type rocker arm. These rocker arms have ears that extend downward, forming a rail or channel over the valve stem. This rail maintains proper alignment. The pushrod passes through a loose tolerance hole in the cylinder head, resulting in a cheaper assembly. At high RPM, however, these rockers can jump the track, loosing alignment with the valve stem and resulting in potentially serious engine damage. These engines do not require hardened pushrods. This scheme was fully adjustable until 1970 when the studs were changed to incorporate a positive stop. The rocker arm nut is no longer used to adjust the valve clearance. Rather it is simply tightened down. Longer or shorter pushrods are selected to adjust the clearance. Since these are non-adjustable they can not be used with mechanical cams.
I have never heard of SBC stuff referred to as "rail" anything. Our stock rocker are self-aligned by virtue of the ball arrangement and not like self-aligning aftermarket roller rockers with the "ears" on them.
I think they might be referring to LS1 style as they are merely tightened down to a particular torque value and not adjusted like the SBC/LT1 ones are.
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Joined: Mar 2000
Posts: 1,955
From: Point Pleasant, NJ... USA
'Real' LT4 heads [on LT4motors] with the 10mm shouldered studs are also tightened to a specific torque, and not 'adjusted' in the usual manner..
The replacement LT4 heads have 'LT1' studs though, and require adjustment...
The replacement LT4 heads have 'LT1' studs though, and require adjustment...
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Joined: Oct 2003
Posts: 2,140
From: DOVER DE
So much bad info in such a small tread.
NSA=non self aligning. These are standard equipment on every smallblock built from 1955 to 1987.
SA=self aligning or rail type. GM started using them in 1987 on car engines and a few years later in the trucks. As stated earlier there is a notch in the rocker tip to keep it centered on the tip of the valve. You can use non self aligning rockers on these heads but you will have to install push rod guide plates and with them hardened pushrods.
Note: Chevy has never to my knowledge used a nonadjustable one size fits all rocker arm set up in any of the small blocks. This includes the LT4 which had stock the very same roller rockers that come in the Hot cam kit.
NSA=non self aligning. These are standard equipment on every smallblock built from 1955 to 1987.
SA=self aligning or rail type. GM started using them in 1987 on car engines and a few years later in the trucks. As stated earlier there is a notch in the rocker tip to keep it centered on the tip of the valve. You can use non self aligning rockers on these heads but you will have to install push rod guide plates and with them hardened pushrods.
Note: Chevy has never to my knowledge used a nonadjustable one size fits all rocker arm set up in any of the small blocks. This includes the LT4 which had stock the very same roller rockers that come in the Hot cam kit.
Registered User
Joined: Dec 1969
Posts: 27,727
From: Little Rock, AR
Originally posted by RE AND CHERYL
So much bad info in such a small tread.
NSA=non self aligning. These are standard equipment on every smallblock built from 1955 to 1987.
SA=self aligning or rail type. GM started using them in 1987 on car engines and a few years later in the trucks. As stated earlier there is a notch in the rocker tip to keep it centered on the tip of the valve. You can use non self aligning rockers on these heads but you will have to install push rod guide plates and with them hardened pushrods.
Note: Chevy has never to my knowledge used a nonadjustable one size fits all rocker arm set up in any of the small blocks. This includes the LT4 which had stock the very same roller rockers that come in the Hot cam kit.
So much bad info in such a small tread.
NSA=non self aligning. These are standard equipment on every smallblock built from 1955 to 1987.
SA=self aligning or rail type. GM started using them in 1987 on car engines and a few years later in the trucks. As stated earlier there is a notch in the rocker tip to keep it centered on the tip of the valve. You can use non self aligning rockers on these heads but you will have to install push rod guide plates and with them hardened pushrods.
Note: Chevy has never to my knowledge used a nonadjustable one size fits all rocker arm set up in any of the small blocks. This includes the LT4 which had stock the very same roller rockers that come in the Hot cam kit.
I also think Charlie is correct about the factory LT4 rockers being different than what was offered in the popular Hot Cam Kit.
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Joined: Mar 2000
Posts: 1,955
From: Point Pleasant, NJ... USA
LT4 heads from LT4 motors have a 7/16" shouldered rocker stud with a 10mm nut.. no adjustment needed they are torqued down..
The Crane rockers while similar to the 'hoitcam' rockers are modified for the larger LT4 stud..
When you buy LT4 'replacement heads' from GM however, they come with LT1 studs[not shouldered..]and specifically mention that fact in the GM ads.. see:
http://www.sdpc2000.com/cart.asp?act...id=277&pid=145
"Supplied with 3/8" rocker studs for use with LT1 engines, instead of the 10mm studs that came on the LT4."
Note here:
http://www.malcams.com/legacy/misc/lt1lt4.html
This paragraph specifically[7th paragraph about 1/3 way down the page]:
"The 1.6:1 roller fulcrum, roller-tipped rocker arms are a modified version of Crane's design. By using these extruded aluminum rocker arms, the engine effectively increases the lift with the added advantage of less engine friction and a smoother idle than the LT1. The rocker arms sit on special shouldered 10mm studs, and are tightened down until they bottom out. This design eliminates the need for any kind of adjustment. "
Also see pics near the bottom of the page of LT1 [pic A]and LT4[pic B] head comparison[NOTE in that pic the 7/16" SHOULDERED LT4 stud]:
http://www.malcams.com/legacy/misc/LT4.htm
Little known but true fact about the LT4..
The Crane rockers while similar to the 'hoitcam' rockers are modified for the larger LT4 stud..
When you buy LT4 'replacement heads' from GM however, they come with LT1 studs[not shouldered..]and specifically mention that fact in the GM ads.. see:
http://www.sdpc2000.com/cart.asp?act...id=277&pid=145
"Supplied with 3/8" rocker studs for use with LT1 engines, instead of the 10mm studs that came on the LT4."
Note here:
http://www.malcams.com/legacy/misc/lt1lt4.html
This paragraph specifically[7th paragraph about 1/3 way down the page]:
"The 1.6:1 roller fulcrum, roller-tipped rocker arms are a modified version of Crane's design. By using these extruded aluminum rocker arms, the engine effectively increases the lift with the added advantage of less engine friction and a smoother idle than the LT1. The rocker arms sit on special shouldered 10mm studs, and are tightened down until they bottom out. This design eliminates the need for any kind of adjustment. "
Also see pics near the bottom of the page of LT1 [pic A]and LT4[pic B] head comparison[NOTE in that pic the 7/16" SHOULDERED LT4 stud]:
http://www.malcams.com/legacy/misc/LT4.htm
Little known but true fact about the LT4..
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