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Unread 02-12-2012, 10:43 AM   #1
slumley1
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Engine Rebuild - How far should I go?

I posted this in the FSJ section but I always get such great support in here for my CJ7 that I decided to post it in here as well. An AMC360/401 is the same regardless of which section it is in. If anyone minds this being posted in here, please remove.

I started with a stock 82 Cherokee with 85k miles. I'm not a mechanic at all and planned to learn as I go. It had an old gummed up 2 barrel carb that I wanted to replace. I decided on an Edelbrock 4 barrel 600 cfm carb. I found that I needed to install a 4 barrel intake manifold so I got an Edelbrock performer Intake. In the process of putting these new parts on I found that there were several cracks in the head and there was so much burnt oil that you could barely even see the valve springs or rockers. I was fortunate to get another set of heads from someone and just picked them up from having them rebuilt. I will have it all the way down to the block before I begin putting the parts back on. Am I making a big mistake by installing the new heads, intake manifold, and carb without rebuilding the block? I was thinking of getting a new block and tehn just slowly build it out of the engine. Perhaps a 401 block. What could I reuse from my 360 and what would I need to replace? Crank, rods, etc? Thoughts?

Any guidance would be greatly appreciated.

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Unread 02-12-2012, 10:44 AM   #2
slumley1
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The block that I'm considering is a 401 block that needs one new sleeve and will need the rest bored. It will also need new crank shaft, rods, cam, etc... The block only is $250. Is that smart or should I just stick with my 360 motor. How much would I be looking at to have the machining done, sleeve, buy pistons, crank shaft (assuming I can't use my 360 crank shaft), and everything else I'd need in order to build this up. The exception is that I don't need to do anything for the heads, intake, carb...just the bottom.
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Unread 02-12-2012, 01:46 PM   #3
slumley1
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I'm also considering just rebuilding my 360 and forgetting the idea of a 401.

Most important question is should I rebuild the bottom while I'm in there?
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Unread 02-12-2012, 02:28 PM   #4
mopar346
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The risk of putting a tight/fresh top end on an older/miled up bottom end is that it MAY cause the rings to start by-passing badly due to the fact that their is now no pressure/compression escape from the top forcing it by the rings. If the bottom is not miled up and tight, you may be fine. I haven't shopped for a 401, but $250 for a junk block doesn't sound like a good deal. I would get a good rebuildable short block, whether it be a 360 or a 401 and start with that. If down time isn't a factor I would pull your and go through it.

A lot of people use the term rebuild for a rering and/or gasket job. A true rebuild includes verifying the cylinder bore and line bores are within tolerance or bore them. Verify the pistons are in tolerance (ring lands) or replacing them. Verifying or machining the crank. Verifying, reconditioning or replacing the rods. I would use a performance cam shaft in as well as a TRU-roller chain while I was at it. If you had the heads at the shop hopefully they checked the springs and set the proper installed pressure and did a minimum of a 3 angle valve job, preferably a 5 angle and in performance applications an 8 angle (as well as some pocket or maybe even some runner porting by a skilled hand WITH a flow bench). In most stock builds the last 20 years I have just used a quality machine shop that offers engine remanufacturing (fancier word for rebuild). They offer a warranty and usely end up cheaper then I can have the machine work done and buy the parts, never mind my time, but I have some guys I trust. I just find it easier. On serious performance I take another approach but that's another story.
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Unread 02-12-2012, 03:22 PM   #5
brownbagg
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it would be nothing to re ring, installed new crank bearing , oil pump and gaskets. about a days work. then it be all nice and fresh and leak free.
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Unread 02-12-2012, 04:08 PM   #6
slumley1
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Thanks guys for the answers so far. Although I've never done this before, I can follow a manual fairly well for some of the work. You guys are great answering questions that up along the way. I'm not in a rush so that's not an issue. My biggest concern is taking the block out. Once I have that out, I can work on it at my own leisure based on time and finances. I'm also a bit concerned about putting it all back once I've built it. How hard is that part? I'm working in my car port.
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Unread 02-12-2012, 08:16 PM   #7
mopar346
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It's pretty basic, one of the beauties of a CJ is it is mechanically simple. Becareful taking it apart and mark everything or take detailed photo and reassemble should be a snap. Set up and adjustments in some cases can be a bear, but between the FSM and here you should be fine. Besides there's only like 10 wires to the engine in the first place.
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Unread 02-16-2012, 07:33 AM   #8
slumley1
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Quote:
Originally Posted by brownbagg
it would be nothing to re ring, installed new crank bearing , oil pump and gaskets. about a days work. then it be all nice and fresh and leak free.
Could I do any of these things without removing the block?
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Unread 02-16-2012, 08:01 AM   #9
hutch1200
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A 401 that needs a sleeve is worth .17 cents/pound. W/o crank etc...forget it. Time is no big deal, good. You may want to buy a short block, w/warranty and put your new heads/intake/carb on it. Take lots of pictures, bag & tag every part. And it doesn't hurt to have a buddy, no matter their mechanical level help w/the removal/installation. It's not neccessarily the hands that you WILL need, it's the EYES that will come in handy when guiding the engine back in, or when you can't figure out where something goes. Good luck!
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Unread 02-16-2012, 11:51 AM   #10
roadhog304
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[QUOTE=hutch1200;13063109]A 401 that needs a sleeve is worth .17 cents/pound.

I am afraid i am going to have to disagree. Not too long ago my engine builder would install a sleeve for $75. These blocks are getting harder and harder to find. I have had several offers to buy my 401's that i have setting in the shop and one is going to need bored 40 or 60 over and guys still want to buy it and take the risk of overboring it. and no they are not for sale.
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Unread 02-17-2012, 07:30 AM   #11
hutch1200
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Really

[quote=roadhog304;13064570]
Quote:
Originally Posted by hutch1200 View Post
A 401 that needs a sleeve is worth .17 cents/pound.

I am afraid i am going to have to disagree. Not too long ago my engine builder would install a sleeve for $75. These blocks are getting harder and harder to find. I have had several offers to buy my 401's that i have setting in the shop and one is going to need bored 40 or 60 over and guys still want to buy it and take the risk of overboring it. and no they are not for sale.
Not doubting you, but ppl still want them w/o crank/heads etc? And for our puroses of low rpm power, a sleeve would not bother me.
I know the 401 bore is the same as the 360 @ 4.165... but the 401 is a stroked to 3.68 vs the 360s' 3.574. So, if I understand, a 401 is just a "stroked" 360. So buying a 401 block you'd need a 401 crank. Or use a 360 crank and you'd have a 360.
I gotta hit the boneyards a LOT harder!
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