Quote:
Originally Posted by Stan Weiss
If under square was the way to go why did Pontiac use the Olds 403 - 4.351" x 3.385"?
Stan
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Simple. 403 came out in 77, replaced applications that used the 455. They needed 400ci +/-, and all small block olds cranks were all 3.385. Only way to get it big enough as a small block was to take the bore out huge. A friend in FL just stuffed an aftermarket 4.00 crank in his 403, its 484" if memory serves. My 350 diesel with 4.00 425 crank and 0.197" overbore ended up 454ci. Still small block.
The olds motor from 1968 to 1976 only had two different combustion chamber sizes, and two different piston dish sizes. They were durable, inexpensive, and did the job. That meant 442s, land barges, jet boats, irrigation pumps, etc. Eight years of production with few changes (besides w-30 specific parts) means that they're quite plentiful, unlike the 455 Pontiac.
I'd love to see two cars of similar weight and gear, one with 428 Poncho and one with 425 Olds, and let them go at it. I'd bet theyd be close.