232 Vs 258

Earlier engines likely have higher compression, which makes a big difference in HP. Ratings changed from gross to net HP in '70-71, causing a meaningless drop in rated HP for all engines. AMC raised the deck and increased the stroke of these engines by 16 thou to increase displacement and make the 304/360/401 engines. A 304 has nearly 5% larger displacement than a 290, and a longer stroke moves the torque peak down in RPM. The new heads are also better than the 290/343/390 heads... so I would expect the actual HP to at least stay the same if not increase. In '72 and '73, we thought the 304 was pretty hot for the CJ-5.

All that said, I'm sure the 290 would be plenty powerful for this Jeep if the OP were happy with it. These engines respond well to some mild hop-ups like free flowing exhaust, 4V manifold and larger carburetor, and a hotter cam. The easiest way to get more power from these engines is to go up in displacement, however.... though finding a 343 (or 390) seems difficult or impossible considering where the OP and his Jeep are located.

 

Awesome, thanks so much for that!!!

 

The 290 that’s in it according to the casting numbers is out of a 67 rambler, high compression 4 barrel. I’d imagine it’s a rare engine, definitely for Australia anyway.... it runs ok so I’ll definitely be keeping it for a future project....
So just to confirm, the engine/ bell housing pattern on the 290 is an early AMC pattern, different to the 71 and up???
Thank you everyone so far for your advice/ opinions

 

Interesting view under the hood. When I look at that, it looks like a factory V8 installation except for two things: the open-element air cleaner, and the high-mount reservoir for the power steering. A factory installation would have used the later can-of-ham power steering reservoir. Otherwise it's just another AMC 304 Jeep in appearance. The battery placement has to move to accommodate RHD. The high-mount oil filter is also correct for a RHD vehicle. That filter setup was available in the USA as service parts for RHD Matadors delivered to the US Postal Service. It was offered to owners in the day as a remote filter kit. When introduced in 1972, the CJ with a V8 could suffer an impact between the front axle housing and the oil pump cover (!!) To prevent this, Jeep would put an extra spacer between the frame and the right axle bumper ... or you could install this kit. Jeep later redesigned the oil pump cover to avoid this issue.

I wonder how the original seats were mounted for RHD. Apparently the tool box is still on the right. The right-side fold and tumble seat that allows access to the back and the toolbox in domestic vehicles would have been blocked by the steering wheel.

 

Nice to see another RHD CJ6 on the road, mine seems to be very similar in spec originally, 232,T14,Dana 20, 4.27 diffs

Mine however has been changed now to an AMC360, T18, Dana20

 

The vote seems to be going towards keeping the 290, so if I were to keep it, what transmission will bolt up to it?
At the moment it has a 5 speed out of a truck. I can only presume it used to be a linkage style shifting transmission that has been converted to a top mount as the shifting pattern is back to front. Example
1 3 5
R 2 4
I used to have a few acres and it’s just weird to drive.
So what transmission would you use?
I would prefer something that’s Jeep with a low 1st gear...

 

Use the T18 you have, all you need is the bellhousing. I've just put one on my CJ6 with a 360, the box came out of and I6 J20 so had the shorter shaft. Great box and easy to work on.

 

Yep, I agree. The T-18 is an excellent choice, though it's not clear whether the CJ V8s ever came with a T-18. Maybe, in that '77-79 period. Same bell we covered earlier - from 1971 on, all the AMC engines have the "unified" pattern developed for the 290/343/390. It will be stock-ish, since the T-18 was a popular option with the 232 and 258 in the '70s.

 

AFAIK the Jeep AMC sixes and V8s were identical to the automobile engines during the years they were offered in both platforms. However, the 290 was never offered in a Jeep, and if it were I would expect it would have been a 2V and 8.4:1 compression (like the '71 304).

 

No. The bell housing pattern is the same as the 232/258/304/360/401. My understanding is the 290/343/390 have a different crankshaft flange from the '72 and up engines. The crankshaft should only matter in terms of the flywheel (which you have) and pilot bushing (which you can modify as needed).

The main difference between the 290 and 304 is the deck height, the stroke, and different heads. No personal experience with the low-deck AMC engines (290/343/390) but I believe they are bolt-in compatible with the high-deck engines (304/360/401). If you have doubts, I suggest you seek confirmation by searching or asking on one of the AMC car sites, like this one The AMC Forum

The sixes change quite a lot across the 1970-71 boundary. Prior to 1971, there was a 199 and a 232. These had the "Rambler six" bolt pattern inherited from the 1950s Nash/AMC 196 engine, with the starter on the left. Like the V8s, in 1971 the deck height and stroke was changed and the 199 became a 232, and the 232 a 258, adopting the same bolt pattern as the current V8s, with the starter on the right. The first generation AMC V8s (250/287/327) are entirely incompatible with any of the other AMC sixes or V8s.

 

This topic 304-290 flywheel differences indicates that they will just bolt together. Note that the poster here wants to use the AX-15 from a 4.0L Jeep, so that's not relevant to what you want. Should just bolt up with the bell I referenced earlier, the T-18 and your 290 with a manual transmission flywheel. You may have to modify or make a pilot bushing to fit in the crank pocket and match the transmission pilot tip - that should be easy.

 

Thank you, I was getting confused with the in-line 6’s different bell housing in the early models.... it certainly would be easier to run what I’ve already got...
The 290 seems to run really well... might be worth giving it a compression test, might not even need a rebuild...
Thanks again for your input
Cheers Danny

 

Do they reproduce the factory air cleaner? I presume the factory air cleaner is to suit a 2100 carb?
My 290 has a 4 barrel manifold and an adapter to a 2100 carb.
Cheers Danny

 

Not sure what came in the 4V passenger cars. Jeep used the Motorcraft 4300 4V carburetor in the '70-74 360s and '74 401s so equipped. That's a Holley square pattern carburetor. If you have an iron manifold, then it's near certain that a PO put the adapter and 2100 on the factory manifold at some point. Your engine has a tag on the valve cover with the build date, and the AMC car guys will know what it came with originally.

The 2V and 4V Holleys and Motorcrafts all have the same diameter air horn, so whatever air cleaner you get is going to fit on all of them.

There's no source for reproduction factory air cleaners AFAIK. However, it should be easy to find a discarded factory-style air cleaner if that's what you want. The car guys seem to value their parts quite highly, so I'd look for sources on the Wagoneer/J-truck forums, www.ifsja.org and www.fsjnetwork.com and also on the generic Jeep sites like JeepForum. The Wagoneer sites have quite a lot of action in parts and parts cars, and you may find what you want there. There are Jeep junkyards too, but an air cleaner should be easy to find private party.

Cheers - glad we could help.