302 pulley bolt holes

[fordman]

what year did for change from 3 bolt holes to 4 on the 302 or small block engine damper? was it 1970? so the early ones have three bolt holes or is it the other way around?

[BobbyFord]

It looks like 3 bolt dampers were available in both 28 and 50 oz. imbalance...
http://www.damperdoctor.com/Merchant2/m ... y_Code=FOR

[FORDification]

Ford 302s used a 3-bolt harmonic balancer on '68-'69 cars and '69-'72 trucks and vans, while the '70 and newer cars use a 4-bolt balancer. The two styles do not readily interchange. The belt offsets are slightly different (not much) but the pulley combo's are way off. The 4-bolt balancers use a wider belt on the PS setup than earlier cars do. In come cases they can be made to work, but in many cases it will cause excess belt wear or shucked belts due to the mismatches.

[Hawkrod]

It looks like 3 bolt dampers were available in both 28 and 50 oz. imbalance...
http://www.damperdoctor.com/Merchant2/m ... y_Code=FOR

3 bolt balancers were never originally avaialable in 50 oz, those are modern balancers made so that you can use newer engines in older vehicles. The 50 oz engine weight did not come out until long after Ford stopped using the 3 bolt pulleys. Hawkrod