Engine Question

[hannaganscr]

I have a 1976 J20 and it has the auto trans. It was a 401 engine but someone has replaced it with a 304. I am wondering is there any engines that are not AMC that I can do a direct bolt in? Like a GM or Ford engine? Any help would be great and thanks. BTW I am new to the FSJ world I have only had mine 6 months.

[BGW]

Nope, the AMC bellhousing pattern is entirely unique. If you're looking for more power, your best bet is to get a 360, build it up, and then swap it for the 304 when you're ready. With a little bit of work, these AMC engines can be absolute monsters. The blocks are very stout, they're made of high grade metal, and they're very easy to "wake up". A new RV cam, 4BBL intake, and 4BBL carb will go a long way, and it's much cheaper than converting to a different type of engine.

[blazer3664]

Can be done, but not financially worth it IMHO.


Motor mount kits are available for a couple different engines here

http://www.bjsoffroad.com/ProdList.asp?scat=79

Say you so GM small block. $195
GM swap radiator http://www.bjsoffroad.com/prod-1079.htm
Can be done cheaper, but say $300

The trans should be a th400, but as BGW mentioned

the AMC bellhousing pattern is entirely unique

So you swap in a GM th400..........but wait....... the tailshaft is also unique.
So you also need to swap the tailshaft from your Jeeps th400 into the GM th400 to mate it to the transfer case. May as well rebuild it while its apart.
.....Lets say you do it all yourself with a master kit like this (cheap on from Summit)http://www.summitracing.com/parts/atp-jms9/overview/
$100
Or you could swap the t-case too, but thats a whole other can of worms.

So just that quick, you are already at $600 by the time you get the little misc stuff to do those.
Add the cost of a GM engine and trans (probably about the same as you could buy a 360 from someone here) and you could do just as BGW mentioned

get a 360, build it up, and then swap it for the 304 when you're ready. With a little bit of work, these AMC engines can be absolute monsters.

Of coarse, if I took my own advice, I wouldn't be putting in a OD trans and doubler. Way more cost than fixing what was there, but its what I want for what I plan to do with it.

So if you WANT a GM/Ford/Dodge engine, go for it, just know it wont be cheaper than getting another AMC V8 in there.

Jim

[joe]

Drop-n bolt-up? No.

[gsmikie]

put your trans guts in a gm th400 case and a set of motor mounts and bolt that 8.1 right in there

[BGW]

put your trans guts in a gm th400 case and a set of motor mounts and bolt that 8.1 right in there

And enjoy burning oil. Far worthier engines to swap than one of those.

[hannaganscr]

Engine swap

I guess you all gave me answer I was looking for. I will start looking for a 401 to put back in it. Thanks for all your help for the noobie..

[Mike D]

you'll have alot more luck finding a 360/390

[mdill]

you'll have alot more luck finding a 360/390

A 390 is going to have some issues, (deck height difference messes up accessory mounting) but any 304, 360, 401 will drop in (with correct flex-plate and dampener) and be form fit compatible , 360 is likely the easiest to find cheap.

[FSJunkie]

Sorry. Chevy engines don't just drop in.

Gee, what a shame...







AMC 360 is a better engine anyway.

[Mike D]

I put in a SBC 283 -- but because i had it and i thought at the time that it would run higher rev's with no ill effects ... (due to the lower gearing)

It was fun making all the changes for it to sit in there ...

it sits still 8 years now -- for other reasons ... (wife, kids -- new house -- the works !!!)

[tgreese]

Realize that the TH400 is an old design, and has a high parasitic load compared to modern lock-up overdrive automatics. And the Quadratrac transfer case has become problematic now due to lack of quality replacement parts ... Even the quality drive chain wears out in about 60K-70K miles, and the import chains wear out much sooner. I expect knowledgeable owners are making plans for a transfer case swap sometime in the future...

Finding a good 401 with a virgin block could be an expensive and time consuming quest. The 401 cannot be overbored much, so a block that has already been bored once may have to be sleeved to be usable. This costs about $100 per hole, IIRC. Check old posts - there's a lot of discussion of this issue with the 401.

So your factory drivetrain has a lot of issues.

What's wrong with the 304? It can power a FSJ just fine. Jeep offered the 304 in the truck and Wagon in '71 and '72, and I expect they dropped the option becasue there was not that much difference between the 304 and 360 2V equipped vehicles.

IMO ... if you don't like the 304, you would be better off to do a complete swap of a modern GM engine, overdrive automatic transmission and modern transfer case. If you pick your components right, all this stuff bolts together and you replace it all. Then all you have to figure out is the mounts, driveshafts, wiring and plumbing.

[hannaganscr]

Engine

I have done some homework and I am thinking about doing a cam swap and aluminum intake with a 4barrel carb. I was told the 304 was rebuilt when I bought the truck so don't really know what all the engine has for specs now. Meaning if its been bored or already has a cam in it. I do know it has a Mallory ignition in it. http://www.youtube.com/watch?v=NJraXikINkk here is a link to a video I done of the truck there are 3 total video's of the truck. I gave $2000 for the truck.

[joe]

Does the 304 "need" rebuilding or you just want more power? Granted in a heavy FSJ a stock 304 isn't a fire breather but it's a solid reliable small V8 and adequate for normal use. But we're talking your money and labor not mine. Vroom Vroom.

[hannaganscr]

Engine

The engine was rebuilt at least that's what I was told anyhow.