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5.3 and 243's

This is a discussion on 5.3 and 243's within the Internal Engine forums, part of the LSx Technical Help Section category; Sorry to ask this but I have been looking at a lot of post and this is really confusing but ...

  1. #1
    Member Speeddemon24_7's Avatar
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    5.3 and 243's

    Sorry to ask this but I have been looking at a lot of post and this is really confusing but here's my questions. I have a 98 Z28 mods in sig. A friend of mine say's he has a set of 243's off of a 2002 5.3L Silverado for $300 dollars. I though 243's and 5.3L heads were two different heads. But if they are not is the only difference between the 243's from the 5.3L and the LS6 243's the light weight valves? Are they the same size valves and CC? How much of a gain would I see from bolting this straight on? and Also If I get them worked what all work would you do and what cam would you go with to have a nice street car like to get 450-500 hp? I have know clue on the best cams for LS1's there is just so much out there? I know there is some other stuff I've got to do to see these type of numbers. Thanks and any help will be greatly appreciated.

    [B]1998 Camaro Z28 [B]M6 SLP Air Lid, K&N, SLP Smooth Bellow, SLP Loudmouth exhaust, MSD wires, NGK Plugs, LS6 Clutch, Pressure Plate, Flywheel, Hurst Short Throw Shifter, Skip-Shift, Clear Corner & Side Markers, White Face Gauges, 15% tint & 18" Chrome Y2K's with 285's

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    Member km346's Avatar
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    5.3's and 243 are two totally different heads. Difference in CC size and valve size. FWIW people have made good power using either set up on ls1 engines. 5.3's have 61cc combustion chambers, and smaller valves whereas 243's have 64cc combustion chambers with larger valves.
    Last edited by km346; 07-16-2010 at 06:26 PM.

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    243 didn't come on 5.3s.look for the casting number on the head.get some 243s for $400 at the ls corvette forums.do a good valve job and install good springs,comp918 etc..if you have the money and know a good head porter ,port the heads.the 243s will add 20 hp .450 rwhp takes great heads and intake,a lot of supporting mods ,and the right cam.it can be done ,whats your budget.

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    Member BKHgto04's Avatar
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    Quote Originally Posted by garygnu65 View Post
    243 didn't come on 5.3s.look for the casting number on the head.get some 243s for $400 at the ls corvette forums.do a good valve job and install good springs,comp918 etc..if you have the money and know a good head porter ,port the heads.the 243s will add 20 hp .450 rwhp takes great heads and intake,a lot of supporting mods ,and the right cam.it can be done ,whats your budget.
    Actually,the 5.3's in the Grand Prix GXP's and in the Monte SS's did come with 243 casting heads,but,those are the only ones.

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    Member Speeddemon24_7's Avatar
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    not sure what I want to spend yet still looking. The guy said that it has 243 on the head and he said that he is pulling them off of his silverado that has a 5.3L. Im still confussed lol.

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    Member Speed_kills_WS6's Avatar
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    They did come on some silverado's with the 5.3L. I've seen them myself. The 6.0's came with 317's.

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    Member rkvette's Avatar
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    actually the 5.3 heads, casting #243, came on all 2006>2009 ss v8 impalas ss. i know i drive a 2008 SS one ,daily!!. i also owned a 2004 zo6 ,with that same number, on its heads.!! rkvette

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