
02-02-2018, 06:49 PM
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CC Member
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Join Date: May 2006
Location: St. Louisville,
Oh
Cobra Make, Engine: A&C 67 427 cobra SB
Posts: 2,445
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Not Ranked
I assume flat tappet mechanical lifters. I have very similar cam specs in a SB only it is hydraulic roller lifters. I can idle it down to 800, but I have EFI. If memory serves it idles about 11"Hg. I would expect more vacuum out of the larger displacement.
From everything you have said, I think it would be worth checking the valve lash.
Take everything I say with a grain of salt. I'm just an armchair enthusiast that owned a 390 FE in 1975. In short, I don't know much.
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