4.320" pistons?

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4.320" pistons?

Post  Galaxie427 on December 27th 2016, 2:42 pm

Just got a free set of pistons, Speed-Pro hypereutectic H535CP "STD". Compression height and pin diameter equate to 460 Ford, but the bore size is only 4.320". What engine would have the ~1.752" CH and ~1.043" pin, but the tiny little bore? Guy I got 'em from claims he used them in his 500" Caddy, but the pistons were too far down in the hole.

Just wonderin'.

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Re: 4.320" pistons?

Post  dfree383 on December 27th 2016, 4:13 pm

You measuring right?
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Re: 4.320" pistons?

Post  DFI429 on December 27th 2016, 4:26 pm

dfree383 wrote:You measuring right?

..Like possibly measuring the very top of the piston?  Google came up with Summit which says stock 460 bore (4.360):

https://www.summitracing.com/parts/slp-h535cp
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Re: 4.320" pistons?

Post  Galaxie427 on December 28th 2016, 3:19 pm

Yeah, above the top ring land. Is that not the best spot? Please go easy on the flaming if I did it wrong.......also, using a cheap digital caliper so it's not TOO accurate..........

Thanks!!
Pete

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Re: 4.320" pistons?

Post  dfree383 on December 28th 2016, 3:41 pm

Wrong place to measure, measure the skirts
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Re: 4.320" pistons?

Post  Galaxie427 on December 29th 2016, 11:31 am

Aha!! 4.357" with my crappy digital caliper on the skirt. Sounds better for an "STD" piston.

Thanks for the lesson!!
Pete

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Re: 4.320" pistons?

Post  gt350hr on December 29th 2016, 2:28 pm

Galaxie427 wrote:Aha!!  4.357" with my crappy digital caliper on the skirt.  Sounds better for an "STD" piston.

Thanks for the lesson!!
Pete


Pete,
As an FYI , the ring land area is undercut from .030-.040 ( manufacturer and bore size dependent) because that area has the highest temperature and therefore most expansion. The skirts are turned "slightly" smaller than the bore because they are flexible and run at much cooler temperatures than the top. this can be as small as .0015 or as big as .010 , again material and manufacturer dependent.

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Re: 4.320" pistons?

Post  Galaxie427 on December 30th 2016, 11:42 am

Thanks! Makes sense to me, now.

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