Stock head differences
02-10-2002, 02:08 PM
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Stock head differences Where can I get info on the diferences between the LS1/LS6 5.7 heads and the 4.8/5.3 and 6.0 truck heads. Just doing some homework for future mods. I have a set of 4.8/5.3 heads that I want to play with. I'm thinking P/P for starters. What kind of valve, spring and rocker upgradesare posible ? I've heard of some puting LS6 springs in and P/P but not much else.
02-10-2002, 03:32 PM
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Re: Stock head differences The LS1/Truck heads have the same port design. The truck heads have a smaller combustion chamber for higher compression ratios. (good) The LS6 has a slightly smaller chamber than the LS1, but not as small as the truck heads. The LS6 and newer 6.0L heads are said to have the same exaust port. But the 6.0L heads have even larger chamber than the LS1, so compression ratio can suffer.
Once ported, the LS6 can be made to flow considerably more than the other castings because of their thickness. On a 346ci LS1, I don't see the need for it. The LS1/Truck heads can easily outflow the limits of the LS6 intake manifold, so the benefit of higher flowing LS6 heads is minimized by the intake manifold. The easiest way to gain horsepower (from one head to another) is with compression. So I think the truck heads are the best way to go.
2.02 1.57 are the largest valve sizes that will fit on the stock valve seats. There is no need on a standard bore LS1 to go any bigger (shrouding) unless money isn't a concern and you want every last cfm you can get out of it. Stock valve sizes are 2.00 and 1.55 on the LS1. The new 2002 LS6 valves are sodium filled and would be the best route but are too darn expensive. The LS6 springs are an upgrade over LS1, but with any good size cams, you want an aftermarket spring with more open/closed pressure. The Comp 918's are becoming popular. Everyone seems to use titanium retainers to lighten up the valvetrain. Comp Cams/REV make a comparable set.
The valve guides are often ok to reuse, but should be checked. Use new GM seals or other Viton valve seals. Always use new Locks, and they have to be 8mm locks. Chevy is the only one I know of that has them. (LS1 specific). You need 8mm valves, Ferrea, Rev, Manley etc are the most popular. Definately go with aftermarket valves and a good valve job. The valve shape makes a significant difference in flow aside from the size. Reuse the stock rocker arms there is no need to upgrade.
And if you port the truck heads, unshroud the valves in the combustion chamber.
Hope that helps,
Scott
Once ported, the LS6 can be made to flow considerably more than the other castings because of their thickness. On a 346ci LS1, I don't see the need for it. The LS1/Truck heads can easily outflow the limits of the LS6 intake manifold, so the benefit of higher flowing LS6 heads is minimized by the intake manifold. The easiest way to gain horsepower (from one head to another) is with compression. So I think the truck heads are the best way to go.
2.02 1.57 are the largest valve sizes that will fit on the stock valve seats. There is no need on a standard bore LS1 to go any bigger (shrouding) unless money isn't a concern and you want every last cfm you can get out of it. Stock valve sizes are 2.00 and 1.55 on the LS1. The new 2002 LS6 valves are sodium filled and would be the best route but are too darn expensive. The LS6 springs are an upgrade over LS1, but with any good size cams, you want an aftermarket spring with more open/closed pressure. The Comp 918's are becoming popular. Everyone seems to use titanium retainers to lighten up the valvetrain. Comp Cams/REV make a comparable set.
The valve guides are often ok to reuse, but should be checked. Use new GM seals or other Viton valve seals. Always use new Locks, and they have to be 8mm locks. Chevy is the only one I know of that has them. (LS1 specific). You need 8mm valves, Ferrea, Rev, Manley etc are the most popular. Definately go with aftermarket valves and a good valve job. The valve shape makes a significant difference in flow aside from the size. Reuse the stock rocker arms there is no need to upgrade.
And if you port the truck heads, unshroud the valves in the combustion chamber.
Hope that helps,
Scott
