3-second answer: A tick that gets louder under load and smells like exhaust = leaking manifold (cracked, or a rusted-off stud). The cheap test: feel for puffs of exhaust at the manifold flange with the engine idling (gloved hand) or watch for soot. Fix: replace the manifold or do the BBK header upgrade — headers fix the tick AND add power, and the BBK shorties bolt on without cutting.
Why they fail
The cast-iron manifolds crack (especially 5.8s) and the studs rust until they snap. The classic "tick at startup that fades" is the manifold sealing once it warms and expands.
The fix options
- Replacement manifold — cheap, stock, but same weakness.
- Headers (BBK shorties) — the community favorite: bolt-on, no floor-pan cutting, fixes leaks for good, ~10-15 hp on a 5.0/5.8. Do it with new exhaust gaskets and copper anti-seize on EVERYTHING.
- Broken studs — the nightmare: they snap flush with the head. Drilling them out is the standard (or leave the broken stud and run a header gasket that covers it — shade-tree but common).
When you're in there
- New gaskets (Fel-Pro)
- Copper anti-seize on all studs/bolts (the single best prevention)
- Check the O2 sensor wiring (the manifolds/headers sit right next to it)
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- FTE search: exhaust manifold · headers