You did say what’s the best. ARP is the best there is. Their exhaust manifold bolts are chromoly. But of course not just any chromoly:
ARP manufactures fasteners from a wide assortment of materials ranging from popular stainless steel and 8740 chrome moly to exotic alloys that have been developed to handle space travel.
You should also know that there are grades within specific alloys. For example, 8740 is available in four grades:
- SDF (guaranteed seamless and defect free).
- CHQ (cold head quality).
- Aircraft.
- Commercial.
ARP uses only the first two (SDF and CHQ), even though they cost more than double “Aircraft” quality.
https://www.summitracing.com/parts/arp-134-1102
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