Pulling a piston, 300 I6
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Junior User
Joined: Sep 2010
Posts: 89
Likes: 1
From: California
Pulling a piston, 300 I6
May sound like a ridiculous question folks but is there any reason I couldn't (or shouldn't) remove a piston thru the bottom. Just don't want to remove the head if I don't have to. After pulling my engine because of a bad knock, I found the #3 rod bearing obliterated. The rest, other than normal wear, check out fine (including out-of-round). Going to install a 10/10 crank kit but #3 is WAY past out of round and needs to be replaced. I've worked as a Ford tech at numerous dealers and independents most of 40+ years but never as a "heavy line" tech. Always as a tune and emissions and don't want to seem like a moron but never been in the bottom end of a 300. Just seemed to be "Gospel" that you pull the pistons thru the top.
Thanks in advance.
Thanks in advance.
Post Fiend
Joined: Jan 2007
Posts: 7,021
Likes: 4
From: Almost Heaven
Hello! Welcome to FTE. You will get the answer to your question shortly. AbandonedBronco or Harte should be coming along shortly.
I really wanted to suggest that you bite the bullet and have the engine gone over with a basic re-build. Sounds like it's time. I think you would be happier that way.
I really wanted to suggest that you bite the bullet and have the engine gone over with a basic re-build. Sounds like it's time. I think you would be happier that way.
Elder User
Joined: Nov 2004
Posts: 666
Likes: 5
I have never done it myself, but I don't think the piston will clear out of the bottom. I could be wrong. However, how would you get the new one back in? You need a flat surface, like the top deck, to make the ring compressor work. I don't see how you would ever be able to compress the rings and put the piston in from the bottom.
Elder User
Joined: Aug 2010
Posts: 567
Likes: 1
From: Vancouver, WA
I doubt you could get a piston out of the bottom without damage to your piston and cylinder. If you can't afford to do it right the first time, how can you afford to redo it corrrectly the second time?
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
A picture I took of the inside of my engine from underneath.
I've never removed a piston, so I don't know what's entailed in the job, but just looking at the picture, it doesn't look like it could be removed without dropping the whole crankshaft out from underneath the engine to make room for it.
Elder User
Joined: Apr 2004
Posts: 970
Likes: 3
Sorry to say you won't get it out,the webs which support the mainsare narrower than the piston diameter. If you were able too get it out how are you going to get it back into the bore? No straight surface to guide the compressed rings back into it. Kotzy
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Senior User
Joined: Jun 2009
Posts: 480
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From: Hudson,Michigan
I would at least pull the head and check the top end,you already have the engine out.I don't know the mileage,but maybe it could use a mild rebuild,your already investing in a bottom end,why not make her good to go?Be sure and check the oil pan for rust and throw a new Melling oil pump in there,nothing like changing a pump after it's in the truck.
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Elder User
Joined: Mar 2008
Posts: 563
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X2,It will come out of the bore,But not out of the block.You would have a very hard time getting it back in if you did.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
I totally concur. Besides, if you are putting new bearings in the bottom end, might as well get a valve job done on the head and replace the rings on all 6 pistons.
New User
Joined: Jul 2010
Posts: 22
Likes: 0
Yep! Gotta pull the head. I just did a complete rebuild. My pop asked me the same question out of curiosity. The last rebuild he did was a flathead in a '51 Merc - about 52 years ago.
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
May sound like a ridiculous question folks but is there any reason I couldn't (or shouldn't) remove a piston thru the bottom. Just don't want to remove the head if I don't have to. After pulling my engine because of a bad knock, I found the #3 rod bearing obliterated. The rest, other than normal wear, check out fine (including out-of-round). Going to install a 10/10 crank kit but #3 is WAY past out of round and needs to be replaced. I've worked as a Ford tech at numerous dealers and independents most of 40+ years but never as a "heavy line" tech. Always as a tune and emissions and don't want to seem like a moron but never been in the bottom end of a 300. Just seemed to be "Gospel" that you pull the pistons thru the top.
Thanks in advance.
Thanks in advance.
Pistons have to come out through the top on most engines, the 300 is no exception. There is only about 3" of space between the main bearing webs.