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.

 

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 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.

 

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?

 

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.

 

And really, taking the head off isn't that big of a deal...

 

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

 

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.

 

Ya you would have to pull the crank to get a piston out the bottom.

 

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.

 

What little trouble you go to to pull the head may save you much grief later and it gives you an opportunity to check the upper end of things, do a valve job while you are at it, etc.

 

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.

 

It would be great to pull the piston out the bottom, but it won't go past the main webs. You'll have to pull the head.

 

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.

 

By 10/10 crank kit do you mean just the bearings, or are you replacing the crankshaft? If one bearing was completely gone, and the journal out of round, the crank will have to be turned or replaced, most likely more than .010". If the other journals are within specs, then a .010" undersize bearing will be way too tight and will cause damage if you can even get the engine started.
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.