MTFCA Forum

Apologies if this topic has been answered before, I searched and did not find this question already discussed.

I am in the gathering parts stage of an engine rebuild. I will be using a Scat stroker crank with the larger than stock main bearing diameters. Different vendors sell various main caps for use with A and Scat stroker cranks. One vendor sells different main caps for A cranks than for Scat stroker cranks. What is the difference in main bearing dimensions between an A crank conversion and a Scat stroker crank?

The Scat crank is made in different main journal diameters, and so you might find caps made to fit each different size. The A cranks are NOT a direct fit into a T, so the main saddles in the block must be trimmed to fit. This A crank main caps have this same treatment

Specifically regarding main caps- because of journal length differences between an A crankshaft and a Scat (or T crank for that matter) the front and rear main cap length for each application is different. You could modify a set of caps intended for a Scat crank for use with an A crankshaft but the rear cap of an A crank set would be too short, requiring thrust surfaces to be very thick. The A crank front cap is shorter on the rear side of the cap for similar reasons.

Is it fact that Scat A and T crankshafts are all machined from the same base forging? If so, might the A sized journals be machined on a T machined crankshaft to get around the variations in main bearing length? That way all that would be needed is a set of replacement caps of standard T width.

Allan from down under.

The Scat large and small journal crankshafts for use in a T block are all machined to the same journal lengths and are the same as a Ford T crankshaft. As above, only when installing an original Ford A crankshaft in a T block are the main cap lengths different from the caps that would be used to install a Scat "T " crank (large or small journal. With that said, the heavy duty caps (large or small journal) made for use with Scat cranks do differ slightly from one another due to the different journal diameters.