amc engines

[81j10honcho]

well for the last 2 nites i discovered that amc used a 400 engine in the 81 j10s as an option but used a 360 block which used a chev crank and pistons which makes me think i have a 400 engine when i searched my vin it came up as a 6.6L and was only tell a couple days ago that was aware of just the 401. ive kinda put all the peices together why i was having a lil trouble finding the rite size of rings for it. please help if any of my info is false i need more education on this. oh and the engine was pulled from a honcho

[Elliott]

That info is false, but it may be a 401. Look under where the engine mounts bolt onto the block and the cast numbers will indicate the CI unless it was a service block. Service blocks will not have a CI under the mounts and it could have been bored to a 401.

[joe]

As Elliott said you learned wrong. FSJ's did have a 401 avail from 74-78 but that's it and it's no relatiion to a Chev in any respect.
Your 81's VIN's 4th digit will read either "C" for the 258 I-6 or "N" for the 360 V8. If it reads anything other than that the VIN plate/title whatever is bogus.

Also as Elliott siad look at the block behind the motor mounts 360/401 etc will be cast into the block. If it is a 401 in your rig it's "been swapped in" and with a good possibility it's already been rebored once.

[waggy401]

As far as I know, the AMC 401s were in production only from 74-78. I'm not quite sure where you got your info, but it's a little off. If you have a 401, it's either not an 81 or is a swapped engine. The 401 is the same as a 360 externally, but internally has a larger bore and other small differences to accomodate the increased stroke. The easiest way to determine the size of your engine is to look at the block from underneath, under the motor mount. It's cast right into the block.

The crank is most certainly not a Chevy part - it's unique to AMC. Some Chevy pistons will interchange, as they are available in almost any size and valve relief design. However, most good parts suppliers have stuff listed specifically for AMC engines.

[joe]

It's also not a 360 bored to 401. Max factory recommended overbore on a 360 is 0.045" which gets you to about 367 CID. Try boring one to 401 and you're drilling for warter.

[FSJ Guy]

There are a lot of morons out there that think the AMC motor is based on Chevy, Ford, etc. I recently had one guy tell me that it was a Buick (or something, I didn't really remember! LOL) patent that the motor was based on. Since I was a guest at his place, I just said "Well, the chevy pushrods will swap over!" and left it at that.

Had he been visiting MY place, it would have been a different story.

Like the others have said, look under (inside, really) the motor mounts with a flashlight and the displacement is cast into the block.

[janie]

Yup, like my brothers have already said. Crawl underneath. When we bought our 79 J-10 (Peso) back in 03, I kinda got my hopes up when we saw a stock 401 air breather sittin up top.

Only way to find out for sure was to throw on a pair of my hubby's coverall's, grab a putty knife and start busting thru 25 + yrs of sludge that had built up on the block.

Sure enough, the numbers read 360.

[fulsizjeep]

The only GM V8 ever installed in a FSJ by whatever company owned Jeep at the time was the Buick Dauntless 350 during the 68 model year up to sometime in the 71 year model.

Some people are not worth debating with on this topic because they are just so dang smart. :banghead:

Here is a REAL 401 for ya:
http://frontier.net/~mystkblu/401part1/images/401part119_JPG.jpg

looking underneath to see the stamp:
http://www.frontier.net/~mystkblu/401part3/images/IMG00085_jpg.jpg

[Rande]

I thought these were Chrysler engines?

[bigun]

I thought these were Chrysler engines?
They aren't?!!!:funny::alc::alc::alc:

[waggy401]

I thought these were Chrysler engines?
When I saw this in my e-mail I immediately went to the forum to say, "You have got to be kidding me!!" Then I saw you have almost 5000 posts. . .:o :rolleyes:

Whew!:p

[bigun]

When I saw this in my e-mail I immediately went to the forum to say, "You have got to be kidding me!!" Then I saw you have almost 5000 posts. . .:o :rolleyes:

Whew!:p
( Best Fog Horn Leghorn voice) IT's a joke son!

[Gambler68]

I did hear that real AMC guys all knew that a 454 crank can be turned down to make a 390/401 stroker...

[Menace]

As far as I know, the AMC 401s were in production only from 74-78. I'm not quite sure where you got your info, but it's a little off.

That's close, but the 401 was actually produced from 1971-78. It just wasn't used in the Jeeps until 1974.
:cool:
Dennis