5.3 heads
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The 5.3L heads have the same valve seats as the 241's and the 243's so in My opinion You can do better by leaving the 1.89's and the 1.55's and just cutting the inner diameter of the seats a little larger . They can be cut to the same as a 1.94 leaving the 1.89's in without as much shrouding by the valve or the side of the combustion chamber . And the exhaust 1's can be cut to the same as a 1.6 . So think about it and take You're pick .
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The 5.3L heads have the same valve seats as the 241's and the 243's so in My opinion You can do better by leaving the 1.89's and the 1.55's and just cutting the inner diameter of the seats a little larger . They can be cut to the same as a 1.94 leaving the 1.89's in without as much shrouding by the valve or the side of the combustion chamber . And the exhaust 1's can be cut to the same as a 1.6 . So think about it and take You're pick .
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I just did this to my 5.3 but didnt have $ for a flow test. I am about to see dyno differences soon, but it wont be a measurement of just the larger valves because i also milled .030" and home ported them.
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i have some ported ls1 heads on my car right now but i would also like to see how big of a differnce the bigger valves and more compresiion will do let me know when you get those dyno numbers back
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Here is what my 2.02/1.60 5.3's did on the flow bench. Can't tell you how they ran because they've never been installed. Project is getting canceled and they are actually for sale in the classifieds.
![](http://i75.photobucket.com/albums/i290/b_shizzle_photos/Engine/CCI12152012_00000.jpg)
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Sale link:
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The 5.3L heads have the same valve seats as the 241's and the 243's so in My opinion You can do better by leaving the 1.89's and the 1.55's and just cutting the inner diameter of the seats a little larger . They can be cut to the same as a 1.94 leaving the 1.89's in without as much shrouding by the valve or the side of the combustion chamber . And the exhaust 1's can be cut to the same as a 1.6 . So think about it and take You're pick .
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I understand ,I have considered doing 1.94 Intake and 1.59 Exhaust on 5.3s and get them ported. The cheapest route would be just do the the Intake side and swap your LS1 2" over , and run with the 1.55 .The 5.3 already has 1.55 on the exhaust side. Get a performance VJ and some light hand port and call it a day.
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To answer the orignal question, I dont think you'd see much if any gain from just the 5.3 to LS1 intake valve swap. They flow the same as they are in stock form. But like others have said with a port job and a cam that needs to breath you will see a difference.
I finally got my 2" valve, .030" mill and home port 5.3 with LS6 cam through a 80e dyno'd. 329 rwhp and 334 tq.
Now itching for a larger cam and stall...
I finally got my 2" valve, .030" mill and home port 5.3 with LS6 cam through a 80e dyno'd. 329 rwhp and 334 tq.
Now itching for a larger cam and stall...