Help me choose a Piston PLEASE

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Mar 12, 2012 | 08:52 PM

Uncle Grumpy

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Junior User

Joined: Sep 2008

Posts: 67

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Help me choose a Piston PLEASE

hi,

I am tearing down my '90 5.8l motor. I am putting together my shopping list but am stuck with the pistons.

The stock pistons have the oval shaped dish that is .110 deep. Looking at Summit & Jegs the only ones like this are the expensive forged type. All the hyper or cast either are .140 or .190 deep.

I t is a sd efi motor am I not doing a radical rebuild so What do I do?

cheers

Mar 12, 2012 | 10:11 PM

restoringmy46

Elder User

Joined: Nov 2004

Posts: 874

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From: Ashland, KY

Get the hypher tech pistons. They are a flat top piston with the 4 valve relief. If your not building a race motor then I'd leave the forged pistons alone.

Mar 12, 2012 | 10:34 PM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

Likes: 1,499

From: Ottawa, Ontario

Nominal CR on a stock '90 5.8 was only about 8.8:1 which means the motor will run without detonation on the cheapest crap gas you can find, so you have some room to bump it up a little without risking the need for higher octane. My 5.8 has those flattops with 4 valve reliefs and it ran great.

Mar 13, 2012 | 07:25 AM

baddad457

Hotshot

Joined: May 2003

Posts: 11,141

Likes: 25

From: south louisiana

The cast replacement pistons usually have a slightly deeper dish to keep the compression ratio at or near the same with an oversize piston. The .14 dish will be fine.