Re: Frod 21A vs 91
I am no engine guy, but big/small end dimensions and length were the same on 48’s. 92a’s and 21a’s. The 21a became the service replacement for the two former. In a letter sent to Ford certified rebuilders that I have a copy of somewhere I believe the 21a’s were designed to be stronger. However as mentioned 91a’s look identical. Would be interesting to weigh a NOS of each
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