Time critical question!!!

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Jul 11, 2018 | 02:55 PM

braol

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Joined: Jan 2018

Posts: 116

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From: Kenosha, WI

Time critical question!!!

I have a neighbor who has what he says is a 390 in his garage. He said I could have it for cheap, but he gave me till Friday to make a decision or it is going to his brother-in-law. How do I definitively test to see if it is a 390 vs. a 360?? I remember somewhere that you pull a plug and measure the stroke from BDC to TDC, I think. What measurement am I looking for????

If I can't figure it out, I might just get it anyways. It would at least give me a spare engine to goof around with...maybe make it a 390, or just rebuild it in stock form if it's a 360 and then replace my 49 year-old motor with a fresh one.

Jul 11, 2018 | 03:09 PM

Freightrain

Lead Driver

Joined: Jan 2003

Posts: 9,893

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From: Ohio

352/360 is 3 1/2" stroke
390 is 3 3/4" stroke.

Should be easy enough to tell the difference. Pull a plug and stick a coat hanger down. When at BDC, mark it. Roll it up and mark it.

Jul 11, 2018 | 07:14 PM

Thipdar

Laughing Gas

Joined: Mar 2010

Posts: 1,028

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From: San Francisco East Bay

Quote:

Originally Posted by braol

Regardless of actual CID, take it, tear it down and (if it's worthwhile) rebuild it so it's ready and waiting... You can check the piston stroke length when it's in YOUR garage

(wish I had one waiting in my garage!)

Jul 11, 2018 | 07:22 PM

JEFFFAFA

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Joined: Mar 2013

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From: Phoenix, Az.

With the crank set at TDC ( Top Dead Center) you measure #1 and #4.

Jul 11, 2018 | 07:42 PM

mrpotatohead

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Joined: Apr 2006

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From: NAMPA, ID.

I've never understood the feeling that a 360 or 352 is a less than desirable engine. There isn't that much difference in them and a 390. My 67 352 was torquey as hell, bone stock.