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#1
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Quote:
This was the first outing of the new 4 inch stroke 421. SY disliked the 3.25 main bearing size because it had a tendency to heat the oil more than the 3 inch mains. Smokey then started the stroker trend we use commonly now by turning 4 inch stroke 3.25 mains down to 3 inches so they could be used in a 389 block. He felt the 3.25 mains were excessive and lobbied the engineers to reduce the size. He wasn't successful in getting the engineers to reduce the main bearing size, and then built the successive engines to his own specs, 4 inch stroke crank with 3 inch main journals used in a 389 block. From my recollection, the starter brace wasn't used until 1964 when Pontiac started using the block to mount the starters. Without the brace the starter bolts have a tendency over time to break the block casting where the starter bolts are tapped into it. The earlier starter mounted either on the bellhousing or the transmission with 7/16 x1" bolts and used lock washers. The block mounted starters used 3/8 x 4 inch bolts. There is much more leverage when the starter engages on a block mounted application, than the early transmission mounted applications, having the tendency to shear things at the weakest link. Below is an example of what can happen to the block without the starter brace on later blocks.
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Brad Yost 1973 T/A (SOLD) 2005 GTO 1984 Grand Prix 100% Pontiacs in my driveway!!! What's in your driveway? If you don't take some of the RACETRACK home with you, Ya got cheated ![]() ![]() ![]()
Last edited by Sirrotica; 02-11-2017 at 12:22 PM. |
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#2
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Thought 61 Pontiac's were still running 389 because 421 was not offered in a production car ( NASCAR Rules ) I know Cotton Owens 61 Pontiac was a 389 for sure.
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