Cam limits for stock setup?
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Joined: Apr 2008
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From: Stockton California
Cam limits for stock setup?
I am in the market for a new camshaft for my 77 l48. I was told by a speed shop that my limits for a cam without changing pistons and what not was 268 adv. duration. I looked this up and it was an exhaust lift of .504, and i thought i remembered hearing someone say that the max lift for stock springs was .5
can anyone shed some light on this for me?
thanks
can anyone shed some light on this for me?
thanks
Drifting
Joined: Feb 2005
Posts: 1,738
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From: San diego ca
like Matt said, higher lift cams / more agressive cams will require higher strength springs both open and seat pressure...your L-48 heads have press in studs which can be an issue with higher spring loads.
In any case, you will want to match a set of springs to the cam you purchase, the cam card will tell you the seat pressure/open pressures the cam requires.
In any case, you will want to match a set of springs to the cam you purchase, the cam card will tell you the seat pressure/open pressures the cam requires.
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From: Stockton California
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
The heads are the biggest hold on how much air you can get in and out of that engine. Even with the exhaust, intake, and cam, you'll be limited.
If you're already buying an intake, plan for a set of cheap used heads that flow better, and will really make use of the rest of the upgrades.
I'm referring to Vortec heads, found in salvage yards all over for around $70 - $100 each. They come from trucks and vans with 5.7L engines from '96 - '00. They can be bolted on with little to no machine work depending on cam. They do require a specific intake, but it seems as though you are already planning to get one of those.
Thread Starter
Advanced
Joined: Apr 2008
Posts: 91
Likes: 0
From: Stockton California
The heads are the biggest hold on how much air you can get in and out of that engine. Even with the exhaust, intake, and cam, you'll be limited.
If you're already buying an intake, plan for a set of cheap used heads that flow better, and will really make use of the rest of the upgrades.
I'm referring to Vortec heads, found in salvage yards all over for around $70 - $100 each. They come from trucks and vans with 5.7L engines from '96 - '00. They can be bolted on with little to no machine work depending on cam. They do require a specific intake, but it seems as though you are already planning to get one of those.
If you're already buying an intake, plan for a set of cheap used heads that flow better, and will really make use of the rest of the upgrades.
I'm referring to Vortec heads, found in salvage yards all over for around $70 - $100 each. They come from trucks and vans with 5.7L engines from '96 - '00. They can be bolted on with little to no machine work depending on cam. They do require a specific intake, but it seems as though you are already planning to get one of those.
An overly-aggressive cam?
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
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Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Depending on how aggressive the cam is the spring pads may need machining to accept higher lift springs and with higher pressures you'll want screw in studs. On top of that, if you won't be using self aligning rockers you'll want the stud bosses machined down for guide plates.
Like I said though, if your can choice doesn't exceed .470" lift you won't need any machine work...assuming the guides and seals are in good shape.
Le Mans Master
Joined: May 2002
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From: Lebanon Township New Jersey
Depending on how aggressive the cam is the spring pads may need machining to accept higher lift springs and with higher pressures you'll want screw in studs. On top of that, if you won't be using self aligning rockers you'll want the stud bosses machined down for guide plates.
Like I said though, if your can choice doesn't exceed .470" lift you won't need any machine work...assuming the guides and seals are in good shape.
Like I said though, if your can choice doesn't exceed .470" lift you won't need any machine work...assuming the guides and seals are in good shape.
Le Mans Master
Joined: Mar 2004
Posts: 7,465
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From: Little Rock AR
There seems to be some confusion about this.The underside of the retainers will hit the tops of the valve guide bosses with too much lift on an unmodified Vortec head. The fix is to cut the top of the guide down a bit for clearance.
Old school production heads would frequently be modified for larger diameter spring pockets as part of a head upgrade. This was done to allow larger diameter springs. The larger diameters were needed to avoid coil bind at higher lifts and still control the valvetrain at high RPM.
Both issues involve machining the heads but for 2 totaly different operations.
I hope this helps.
-Mark.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
That's what I meant I just keep saying spring pads instead of guide bosses. I knew what I meant but failed to say it properly.
Last edited by Durango_Boy; Jul 3, 2008 at 04:18 PM.
