When Do You Need Screw In Rocker Studs
Thread Starter
Pro
Joined: Feb 2007
Posts: 548
Likes: 1
From: Victoria VA
When Do You Need Screw In Rocker Studs
I want some info from you all on when you would need screw in rocker studs. I was thinking that when in a hi valve spring tenisin and hi rpms they will be neded. But in a engine build where the rpms will be under 6000 are they needed?
Racer
Joined: Dec 2006
Posts: 417
Likes: 40
From: Swansea IL
Screw-in studs were used in high performance engines (Hi RPM). The factory started that in the SBC in 1970 on the LT1 I believe.
Prior to that, even the hi horse, hi RPM SBCs were pressed in studs. When valve spring seat pressures started to climb, people drilled the head boss and stud and pinned them in.
Up to 6K or below, they probably are not necessary.
Bob
Prior to that, even the hi horse, hi RPM SBCs were pressed in studs. When valve spring seat pressures started to climb, people drilled the head boss and stud and pinned them in.
Up to 6K or below, they probably are not necessary.
Bob
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
your valve spring pressure determines it.....i don't recall off hand what the threshold is but its not a secret and is widely published
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
All SB Chevies had same valve springs. GM went to screw in studs after many warranty problems with 1969 Z/28 engines. So I would say if under 6000RPM and light vale springs then, press-in studs are OK but if HIGH RPM even with weak springs, go with screw-ins. If you upgrade to "Z/28 springs" they are in fact designed for #140 "off-road" cam listed in Z/28 racing manual for SCCA Trans-Am and I would run screw-in studs. Thats just me talking, I don't like to drop valves into my motors after I spent all that money on them.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Crane cams recomends screw in studs if valve spring open
pressure goes over 280. I would want screw in studs as
an insurance policy but having said that I have not seen
anyone come on the forum with the vortech head and a flat
tappit hydraulic complaining of a pulled stud.
pressure goes over 280. I would want screw in studs as
an insurance policy but having said that I have not seen
anyone come on the forum with the vortech head and a flat
tappit hydraulic complaining of a pulled stud.
Last edited by Little Mouse; Mar 30, 2007 at 12:35 AM.
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
If the L-82 needed them, you can pretty much say that yes, you do need them if you have a performance cam in there. GM did not put them in there because they look cool with the valve covers off. Money was spent where it was required. The loads come from the RPM, spring rate, camshaft lift rate, etc.
-Mark.
-Mark.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
I've always heard 300 lbs over the nose was the point where you needed to convert.
How can you drop a valve when a stud pulls out? That valve stays shut and quits moving. Valves drop when they bend and get stuck open, break a spring or have problems with the spring/retainer setup.
How can you drop a valve when a stud pulls out? That valve stays shut and quits moving. Valves drop when they bend and get stuck open, break a spring or have problems with the spring/retainer setup.
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Race Director
Joined: Jan 2003
Posts: 15,176
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From: State of Confusion
I had same thing happen w/ L79 cam and matching valve-springs:
from that time forward, if the heads come-off the block, screw-in studs are in them when they go back!
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
A good general rule of thumb for screw in studs is the valve lift. Anthing over .450 lift in a SB needs studs. A) Because you need more spring for more lift, B) Cams with with .450 lift rarely rev over 5500.
I have ran an old isky 280/.480 cam in the past with pressed in with no problems but it was on a budget(ie. junk) motor.
On my dad's 358" I just built, we went with the XE 268 wtih .474/.490 lift and I had the machine shop install screw in studs in the stock double hump heads. It will rarely spin over 5k rpms but I didn't want to chance it.
I have ran an old isky 280/.480 cam in the past with pressed in with no problems but it was on a budget(ie. junk) motor.
On my dad's 358" I just built, we went with the XE 268 wtih .474/.490 lift and I had the machine shop install screw in studs in the stock double hump heads. It will rarely spin over 5k rpms but I didn't want to chance it.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Also, I have a crane blueprint cam of the old 327/350hp(L79) and it has .447 lift and I am using the stock studs and have been with this cam for 40k miles. But this thing can BARELY rev to 5k rpms so rpms are not an issue for my studs.
