360, idles great stumbles uptop

'79 360 flat tappet cam engine.

Is that the original cam and lifters yet?

Original heads... kind of sounds like valve float. Original weak, lost tension valve springs. Cams start to wear rounding the peaks off not fully opening the valves at rpm.

Take a heat temp gun and check header exhaust temp at the head exhaust ports. Should be 400° or so.

If running cooler, probably needs more fuel.


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