Engine Curiosities - JeepForum.com
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post #1 of 18 Old 10-24-2017, 08:21 PM Thread Starter
jeeptastic75
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Cj Engine Curiosities

Ok guys & gals, first off, I'd like to thank EVERYONE who has posted on here in the past. This forum has become my go-to for overall learning, answering questions I haven't thought to ask yet, and just great information in general. I bought a 1975 CJ5 (my first jeep) a little while ago and have enjoyed it thoroughly this summer! However, as part of a christmas/birthday/new years present to myself, I'm beginning the restoration process for this little beauty! I've come across a couple of things, however, that I would like to see if the fine people here could perhaps clear up for me.

1) The engine stamp on the side of the block shows serial # 703A23, which according to a breakdown of that number I found on this site, equates to the following: 7=1974; 03=March; A=258 1bbl; 23=23rd of March.

However, if this is a 1975 VIN Jeep, could this be a replaced motor, or would the manufacturer have just used an engine that was made in 1974? I ask this not only since I'm a newbie at this whole Jeep restoration thing, but also because I understand that most (if not all) car models come out a year before the year model they actually are (as in, a 2018 Ford is actually released in 2017).

2) When attempting to perform my first oil change, I bought a replacement oil filter from my auto store only to get home and find that it did not evenly remotely fit, nor did the shape of the two filters look the same. Strange indeed. After cross-referencing the original oil filter to one on the k&n site, it seems that the oil filter is an HP-1007, which is designed to fit in a 1983 Jeep CJ5 4.2L engine???

So my question is, if the engine serial number says its made in 1974, then how the heck can neither the 1974 nor 1975 oil filters fit, but a 1983 one does??

I appreciate any feedback and knowledge that you men and/or ladies are able to offer! I've attached a few photos of the engine for reference in case it would help. Thanks in advance!!

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IMG_20171024_210935.jpg   IMG_20171024_211009.jpg   IMG_20171024_211024.jpg  
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post #2 of 18 Old 10-25-2017, 12:56 PM
GreasyJeeper
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As we all know, AMC was well known for using parts from all over the place. That would probably include using engines from the previous year. I would think that is a common practice. Why throw out a perfectly good engine just because the model year changes. Although, somewhat of a horror story to gear heads, back in the 70's, my dad and I serviced equipment for AMC in Kenosha, WI. My dad could not believe his eyes when he came upon a worker cracking the blocks on brand new engines with a sledge hammer! When he asked him why, the worker told him that they were surplus engines, and had to be destroyed before going to the scrap yard so that they could not be resold! Go figure!
As for the oil filter, I know that some vehicles have less room where the oil filter is located depending on options, etc. So, the same vehicle with the same engine might require different oil filters depending what is installed under the hood.
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post #3 of 18 Old 10-25-2017, 01:42 PM
Dngrs1
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What filter did the auto parts store sell you? The 258 in my CJ ('79) takes a KN HP 2003, Fram PH11 or PH25 (one is shorter), STP S25 or Mobil M1-203. Your engine should also take one of these. Maybe the PO had the wrong filter on there to begin with. As far as the date of build, I think the engines were built in the spring to be installed in the fall for the next years models.

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post #4 of 18 Old 10-25-2017, 01:44 PM
bob4703
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If you still have the VIN decal on the dash it will tell you the month of production--at least the 74 on did. You may find that the gap between engine production and vehicle production is closer than you think.

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post #5 of 18 Old 10-25-2017, 02:15 PM
james04si
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the engine looks to be older. By 81 the intake was aluminum and did not bolt directly to the exhaust like your pictures show. also somewhere after the 70's they changed the paint to black from the amc blue. Sometimes the correct oil filter doesnt fit because the motor mounts have moved/flattened some and the original sized one is a tight fit.
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post #6 of 18 Old 10-25-2017, 02:47 PM
bob4703
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Engine looks appropriate for an intermediate Jeep. Valve cove and engine was painted AMC blue at one time.

If memory serves me correctly the number on the block is the casting date and not the assembly date.

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post #7 of 18 Old 10-25-2017, 02:56 PM
Matt1981CJ7
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Yeah, I'd say that's a '74 engine in a '75 model year CJ. It's pretty common for the engine to be a year older than the model year.

I'm not sure what happened with your oil filter, but I'm guessing some parts flunky gave you the wrong one.

Matt


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post #8 of 18 Old 10-25-2017, 02:57 PM Thread Starter
jeeptastic75
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The original filter I had was the K&N HP 2003, but that didn't remotely fit, nor did it look the same (physically) as the one that was already on there.
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post #9 of 18 Old 10-25-2017, 03:02 PM Thread Starter
jeeptastic75
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Thanks for all the info, everyone!! I'm primarily in the research phase of my restore and I don't want to waste time buying the wrong parts just in case I've missed something dealing with the engine. I'm also still on the fence of rebuilding the engine vs buying a replacement. Like I said, I'm new to this, so I'm trying to do as much research as possible beforehand to help mitigate any lengthy lessons that can only be learned through the pain of failure haha.
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post #10 of 18 Old 10-25-2017, 09:00 PM
LumpyGrits
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My 85 uses a Fram PH3675 oil filter and specs Wix(OEM)NAPA 1522.
When did the oil filters change in PN's?
LG

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post #11 of 18 Old 10-26-2017, 09:37 AM
pedal2themetai
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Hi, All 258's would take the same type oil filter.. So you may have got the wrong one from the parts store.. the 258 is a 4.2 litter. Your motor is factory stock for that year. Don't worry about building and selling before they actually year of the jeep.. that is taken into consideration when building from the factory.. it does NOT matter if the motor is for a 74 or an 83 they would all take the same filter..
your over thinking this.
good luck
tim
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post #12 of 18 Old 10-26-2017, 11:03 AM
skizriz
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Quote:
Originally Posted by pedal2themetai View Post
Hi, All 258's would take the same type oil filter.. So you may have got the wrong one from the parts store.. the 258 is a 4.2 litter. Your motor is factory stock for that year. Don't worry about building and selling before they actually year of the jeep.. that is taken into consideration when building from the factory.. it does NOT matter if the motor is for a 74 or an 83 they would all take the same filter..
your over thinking this.
good luck
tim
My 78 actually took a bigger outside diameter filter. I ran one from a newer year though, as it was smaller diameter and didn't get dented from the motor mount.

They are interchangable, newer years are just a lot smaller than older years.
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post #13 of 18 Old 10-27-2017, 12:37 PM
BushPusher77
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Also looks like you have a prestolite distributor and ignition setup for future reference
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post #14 of 18 Old 10-27-2017, 12:51 PM
LumpyGrits
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The date on the block is the casting date.
Most iron block makers let the blocks sit for a year or so as the iron will age harden during this time.
My '85 I bought new in March of '85, has a late 83 date stamp on the block.
LG

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post #15 of 18 Old 10-27-2017, 09:25 PM
whollsee
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Quote:
Originally Posted by LumpyGrits View Post
The date on the block is the casting date.
Most iron block makers let the blocks sit for a year or so as the iron will age harden during this time.
My '85 I bought new in March of '85, has a late 83 date stamp on the block.
LG
yep one of my 258's , both are original, has an 85 head and an 82 block . The casting number on my 82 engine block indicates it is newer by 10 days or so than the block on the 85.

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