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Quote the bolt Size as 9/16-18 X 1-3/4”, this is not the bolt head, and the early 144 is 55lb-ft bolt toque, and the later 170/200 engines were 85-95lb-ft
From page 25 to 33 of
http://www.melvinsclassicfordparts.com/ ... _25-33.pdf
Stock early SBF Windsors before the serpentine belt balancer were 5/8-18 threads per inch X 1-3/4” 15/16” Hex Bolt that is U$ 4.00 for AMK1191, Same as any SBF 221-260-289-351w, to BB 332-352-360-361-390-391-406-427-428, and 385 series 370-429-460 (
except the SBF 351C)
Stock I6's were 9/16-18 X 1-3/4” U$ 4.50 for AMK281
The bolt is an "ARP #150-2501 balancer bolt and washer fits ford v8
except 351C and inline 6". Its a 5/8-18 RH Thread Underhead Length (in): 2.050 in, Overall Length (in):2.87 (for 79-95 5.0L Windsors)
The ARP #150-2503 also doesn't fit, it fits ford v8
except 351C and inline 6 and others not listed. Its a 5/8-18 RH Thread, Underhead Length (in): 1.880 in (for 70-83 302C/351C)
The answer is simple...I'd say Ford changed the front bolt not at all, and the front balancer bolt was accidently wrong from Mike
because of a mistake by ARP. The missing ARP #150-2502 balancer bolt is what it should be, but ARP don't make one.....