823 with 821

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09-28-2020, 03:40 PM

Dr1rrrr

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823 with 821

I'm rebuilding a gen 4 ls and I only have one 823 head and the only ones I can find used for a reasonable price is 821 can these be used together? I know some cathedral port heads can so I was wondering if these can

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09-28-2020, 04:18 PM

G Atsma

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You should be OK with that. The 821 came on the LS3 with different valves (same sizes) and seat grind configuration.

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09-28-2020, 05:59 PM

low2001gmc

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I'm picky and don't like the idea of running an 821 with lighter hollow stem intake valves and an 823 with heavier intake valves, but to each their own.