At what point do i overbore a 401 block

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   You can still buy 0.020" over in cast:https://www.ebay.com/itm/142993900497?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D257838%26meid%3D44ee5a9466674addb9b953910ed808f0%26pid%3D101195%26rk%3D3%26rkt%3D12%26sd%3D154449245104%26itm%3D142993900497%26pmt%3D1%26noa%3D0%26pg%3D4429486%26algv%3DSimplAMLv11WebTrimmedV3MskuWithLambda85KnnRecallV1V2V4ItemNrtInQueryAndCassiniVisualRankerAndBertRecallWithVMEV3CPCAuto&_trksid=p4429486.c101195.m1851&amdata=cksum%3A14299390049744ee5a9466674addb9b953910ed808f0%7Cenc%3AAQAIAAABUObhgc4Nk8%252BdtAwOww4FKLaj%252FQ5qqgDlQCuqZA43WcPFUWDERCUugbbOk7XQv0JXlBfqCg2xKF3WcPghxGMFw2oSlXvfExEaMYr7I7LmrHcP6czY1wIMt0ORyKiCWt95xldincyyBx3g%252BNDW%252B%252FhWUgTaBhK6xAm%252BJIbCOMehu%252BdwjaUbUHW4CB3CdN%252B0sBPp9%252BG0CTcyEdsMii6hprdQGEfEDEUUZgzDOkq86nOVzlwktB5qU2VF%252FF0UmGode8FHT%252Bp5hAQE4k0Q1KxF8sKgRxJGckviPDovh3TFcuFBbjwAtTVJ7ypMiaTeVsmlaecvGoQnINqy4QpjN9HhGDBS57z7GA1eDH0uv%252ByPeF3iIa7leDhSS5Xe2h7dggj%252BuldEn1IB6AjxtPEU%252FdLsIwANOnG4nSWXGH4aCrDzMTAkHVQNGvWuidN81uSc1Ll3EvJk7w%253D%253D%7Campid%3APL_CLK%7Cclp%3A4429486
Local person has a 401 built with these and dyno 426 HP on these cast pistons 91 octane fuel.
Builder stated that forged were not required for this HP peaking below 5000 RPM.
Engine still runs well, but just used for the street.

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Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6909	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Dec/05/2023 at 1:41pm
	You can still buy 0.020" over in cast: https://www.ebay.com/itm/142993900497?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D257838%26meid%3D44ee5a9466674addb9b953910ed808f0%26pid%3D101195%26rk%3D3%26rkt%3D12%26sd%3D154449245104%26itm%3D142993900497%26pmt%3D1%26noa%3D0%26pg%3D4429486%26algv%3DSimplAMLv11WebTrimmedV3MskuWithLambda85KnnRecallV1V2V4ItemNrtInQueryAndCassiniVisualRankerAndBertRecallWithVMEV3CPCAuto&_trksid=p4429486.c101195.m1851&amdata=cksum%3A14299390049744ee5a9466674addb9b953910ed808f0%7Cenc%3AAQAIAAABUObhgc4Nk8%252BdtAwOww4FKLaj%252FQ5qqgDlQCuqZA43WcPFUWDERCUugbbOk7XQv0JXlBfqCg2xKF3WcPghxGMFw2oSlXvfExEaMYr7I7LmrHcP6czY1wIMt0ORyKiCWt95xldincyyBx3g%252BNDW%252B%252FhWUgTaBhK6xAm%252BJIbCOMehu%252BdwjaUbUHW4CB3CdN%252B0sBPp9%252BG0CTcyEdsMii6hprdQGEfEDEUUZgzDOkq86nOVzlwktB5qU2VF%252FF0UmGode8FHT%252Bp5hAQE4k0Q1KxF8sKgRxJGckviPDovh3TFcuFBbjwAtTVJ7ypMiaTeVsmlaecvGoQnINqy4QpjN9HhGDBS57z7GA1eDH0uv%252ByPeF3iIa7leDhSS5Xe2h7dggj%252BuldEn1IB6AjxtPEU%252FdLsIwANOnG4nSWXGH4aCrDzMTAkHVQNGvWuidN81uSc1Ll3EvJk7w%253D%253D%7Campid%3APL_CLK%7Cclp%3A4429486 Local person has a 401 built with these and dyno 426 HP on these cast pistons 91 octane fuel. Builder stated that forged were not required for this HP peaking below 5000 RPM. Engine still runs well, but just used for the street.

Jeff Lee Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: May/14/2023 Location: Anthem AZ Status: Offline Points: 159	Post Options Post Reply Quote Jeff Lee Report Post Thanks(0) Quote Reply Posted: Dec/06/2023 at 8:41am
	Just an FYI - you can get custom pistons at ANY bore size. And considering the cost of 390 /401 standard bore blocks, this may actually pencil out economically. Believe it or not, I just had a set of pistons built that weee only .003” larger than the set I replaced. I had two bad pistons and wanted to change the ring configurations. I’m also limited to the amount I can overbore by class rules. Yes, I realize that’s not for everyone but maybe you have a block that was cheap or even free and finding something “better” is now $1500+. I use Gibtech pistons and 8 new pistons and pins were $1,450 w/ shipping and 6-week turnaround (depending on engineering changes you may have; custom domes, etc). And that’s a 433 gram 2618 material piston with perfect tolerances.