05-12-2025, 10:11 AM

oldman66gto oldman66gto is offline

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Join Date: May 2025

Location: St. Augustine Fl

Posts: 71

Exhaust Manifold Performance Stock vs HO

Does anyone know of what advantages the "HO" exhaust manifolds have over "Stock" exhaust manifolds?

I have the 9777646 (left) HO manifolds on my '66 GTO, which has a 428 in it.

I am curious if there is much gain over "stock"?

Thanks in advance for your input & knowledge.

Just an ol man trying to learn

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