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03-04-2021, 02:16 PM | #1 |
Junior Member
Join Date: Mar 2021
Posts: 2
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Flat head pistons
I have the 4 ring FH v8 pistons. Can I leave off the bottom oil ring and run them with 3 rings?
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03-04-2021, 02:47 PM | #2 |
Senior Member
Join Date: May 2010
Location: Oshkosh, Wi
Posts: 4,525
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Re: Flat head pistons
Leave it off. I don't use the 4th ring on any of my builds.
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03-04-2021, 02:48 PM | #3 |
Senior Member
Join Date: May 2017
Location: Arkansas
Posts: 611
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Re: Flat head pistons
I saw the replies over on the other forum, there are some differing opinions over here. After a lot of reading, I've left that bottom ring out of two engines and am getting ready to on a third. Experts will be along soon.
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03-04-2021, 02:54 PM | #4 |
Senior Member
Join Date: May 2010
Location: Charlotte NC KiWi-L100 available here
Posts: 2,954
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Re: Flat head pistons
What FlatJack says you can’t go wrong.
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03-04-2021, 03:22 PM | #5 |
Senior Member
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 10,302
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Re: Flat head pistons
I left 'em off my last build with no ill effects. I did have the assembly balanced that way to make sure.
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03-04-2021, 03:24 PM | #6 |
Senior Member
Join Date: May 2010
Location: albany
Posts: 465
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Re: Flat head pistons
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03-04-2021, 03:31 PM | #7 |
Senior Member
Join Date: May 2010
Location: Under A Clean V8
Posts: 228
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Re: Flat head pistons
It's been done for years, 4 ring pistons with only 3 rings,
You are not breaking new ground or forging new territory here. moe |
03-04-2021, 03:40 PM | #8 |
Senior Member
Join Date: May 2010
Location: Chester Vt
Posts: 8,855
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Re: Flat head pistons
I also chop off the bottom of the piston as well. But, You have to be carful here. Most of these pistons are "Auto -thermic" and have a steel strut in them. I make a clamp for the ring area to clamp in the lathe as not to hurt the ring stack. This brings the weight down to to an Egge piston . Now you say "What about balancing" IF ( BIG IF) your using the original crank and rods, not to worry. If not, you have to have it balanced any way.
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03-04-2021, 05:58 PM | #9 |
Member Emeritus
Join Date: May 2010
Location: Fitzgerald, Georgia
Posts: 2,204
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Re: Flat head pistons
Again it is time for some real facts--it depends on the rings you are using. If you are using the dual scraper oil ring with expander, omitting the 4th ring is completely acceptable or even preferred. If you are using the original type, one piece oil rings it is better to install all 4 of the rings.
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03-04-2021, 07:12 PM | #10 |
Senior Member
Join Date: Oct 2019
Location: Carthage , Tennessee
Posts: 199
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Re: Flat head pistons
JWL,,,,,thank you for the info.
It always helps to have detailed reasoning with the answers . Makes complete sense to me ! Tommy |
03-06-2021, 04:41 PM | #11 |
Junior Member
Join Date: Mar 2021
Posts: 2
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Re: Flat head pistons
Thanks everyone for your repies! I couldn't see any reason that they couldn't be run with 3 rings, just needed a little reasurance. Deen
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