Safe lift with press in studs?
03-23-2008 | 06:26 PM
#1
Thread Starter
Junior Member
Joined: Dec 2007
Posts: 14
Likes: 0
Safe lift with press in studs?
hello. I have my vortec heads at the machine shop. What is the safe lift with press in studs? I realy don't want to spend an extra $200.00 if it will work with my .480 lift cam. Thanks. Bryan
03-23-2008 | 06:33 PM
#2
Moderator
Joined: Jul 1999
Posts: 17,171
Likes: 138
From: 51°N 114°W, 3500'
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: Safe lift with press in studs?
There is no "safe lift" with press in studs. Stamped steel rockers only have so much travel before they hit the stud but using roller rockers or long slot rockers solve that problem. Factory rockers are usually safe to around .500 lift.
The problem with press in studs is spring pressure. Typical factory spring pressure is 80-100 pounds seat pressure. If spring pressure is too high, it can pull the studs out of the head as the rocker is trying to open the valve. Having open pressure in the 250+ range really needs screw in studs.
The problem with press in studs is spring pressure. Typical factory spring pressure is 80-100 pounds seat pressure. If spring pressure is too high, it can pull the studs out of the head as the rocker is trying to open the valve. Having open pressure in the 250+ range really needs screw in studs.
03-23-2008 | 06:39 PM
#3
Member
Joined: Jan 2008
Posts: 274
Likes: 0
From: Kitchener, ONT
Car: 2000 SS, M6
Engine: Modified LS1
Transmission: T-56
Axle/Gears: 3.42
Re: Safe lift with press in studs?
Good answer Stephen
In addition to that, even a low spring pressure can cause issues with press
in studs at high RPM.
The faster the opening velocity, the more stress placed on the stud.
Therefore even a stock spring type pressure can be too much for a quick
opening valve at 5000+ RPM.
Spend the money and do it right if you plan to buzz this motor to the moon
frequently.
In addition to that, even a low spring pressure can cause issues with press
in studs at high RPM.
The faster the opening velocity, the more stress placed on the stud.
Therefore even a stock spring type pressure can be too much for a quick
opening valve at 5000+ RPM.
Spend the money and do it right if you plan to buzz this motor to the moon
frequently.
03-23-2008 | 06:52 PM
#4
Supreme Member
Joined: Sep 2001
Posts: 6,111
Likes: 52
From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
Re: Safe lift with press in studs?
You can drill and roll pin the rocker studs yourself for a few $$$s
03-24-2008 | 09:31 AM
#5
Member
Joined: Jul 2006
Posts: 167
Likes: 0
From: upstate NY
Car: 88 GTA
Engine: 355
Transmission: TH350
Axle/Gears: 3.42 Auburn Pro
Re: Safe lift with press in studs?
I think if the heads are already at the machine shop it would be silly not to have it done. Even if they are fine with your current cam you will be limited in the future.
Thread
Thread Starter
Forum
Replies
Last Post
355tpipickup
Tech / General Engine
9
09-13-2015 11:35 PM
