V8 Swap

Forgive me if this has been discussed many times before, but I didn't seem to find anything in my searches. My 75 came with a 258, and had a 232 swapped in at some point. I was going to run that until a buddy told me he had a complete and running (when it pulled it last summer) 304. What do I need to do to get it to mount between the frame rails? Do I need to replace the motor mounts, or will the inline 6 mounts bolt up?

Also, the guy I got the Jeep from swore up and down it had a T15, but somehow I wouldn't be suprised if it was a T14. Will the motor bolt up to a T14 and can I use it for the short term to move it around the yard under its own power?

Are there any other issues that I should be aware of, or is it pretty much bolt in?

 

There will always be issues. The fuel will need to be switched to the other frame rail.
If you can score the under hood engine wire harness that will help you. It plugs into the left side of the wiring block on the firewall. Where I have my bare spades plugged into.



I believe the passenger frame tower has to be replaced. this is a complete CJ/AMC V8 set up.

 

Thanks for the info. Can I just use the I6 wiring harness plug and splice new wires on to it for the engine?

At this point, I'm not trying to get it to run (although that would be nice). I just physically want it bolted in under the hood.

 

Yes you can, it just would make it easier.

 

JMO - if you are going to do a swap, do the best swap you can.

You can do the 304, but there will be many little things to change. And a 304 is a compromise if you are doing a swap, because a 360 will fit identically (except for a different flywheel) and will give you significantly more power for cheap. The 304 is fine, but it does not make much sense to use it anywhere except the chassis it came in.

One of the two frame brackets for the engine mounts changes. You need the 304 engine brackets for the same era CJ.

The driveshafts are different lengths. The position of the cross member will be different. The clutch linkage is different. TC shifter length is different IIRC.

Personally I think you would be much better off with a 4.0L than a 304. The gas mileage will be much better, the 4.0L sits on the 258 mounts with no changes, and the excellent Mopar TBI can be used without any retuning.

The T-14 won't hold up long to the 304 or a 4.0L. The factory 4.0L makes close to the HP of a 360.

If I were buying this Jeep, and it had a VIN that said 258 and it had a 304, I'd probably pass. Most likely I would be buying somebody else's problems. JMO.

 

Don't guess - get under the Jeep and read the numbers CAST IN TO THE CASE.

Unlikely you have a T-15, since it is a slightly different length from a T-14 and would cause engine change issues.

PO's are notoriously clueless, unless they are enthusiasts.

 

The guy I got it from is a pretty hard core Jeeper. And looking at this Jeep, nothing would surprise me. I know it's a 3 speed. Now if it's a T14, T15, or a T150 is beyond me. I was reading that because the T14 is shorter, it uses the front set of crossmember bolt holes and the T15 uses the rear ones. For that reason, I assumed the plane of the Engine/Bellhousing mounting surface was in the same spot for both transmissions.

As for the Jeep, I traded a 231J for it, so I'm not in much. The carb is seized and by the looks of it, somebody converted it to points. Engine turns free and cranks. Going over the cost to get the engine running, it seems cheaper to get the 304 and have something that actually starts.

In any event, the 304 is cheap enough that I could turn it around for a profit if it looks like it's too much of a hassle.

I've got a spare 4.0 in the garage, but that was planned for a stroker build for the XJ. Originally I got the CJ just for the 258, then discovered the casting numbers say it's a 232.

 

So you can read the casting numbers on the engine but not on the transmission? Just get under there and read 13-07 or T15 for a T15 and 13-02 or T14A for a T14. Big letters on the side of the case. Easy.

Anyway, the casting numbers don't tell you if it's a 232 or a 258. Both engines use the same castings... same bore, different stroke. The engine code is stamped into the side of the block - that will tell you the displacement. The code is "YMMXDD" where Y M and D are the year, month and day of production, and X is the engine type, either A or B (258) or E or F (232).

 

I meant the engine code.

I believe when I looked it up, that came out to be a 1977 232.

 

There you go. June 22, 1977. E = 1V 232 with the standard 8:1 compression.

Sloppy stamping job by AMC!

 

I swaped a 304 in a 79 that threw a rod on the 258. It was simple, only one motor mount needs changed and it bolts on, the fuel lines run down the opposite frame rail because the carb fuel inlet is on the opposite side than the 258 carb. For the wiring though, mine had electronic ignition and the module must have went out during the swap as we had no spark. I had a points dist and we wired it up, started and ran great. drove it for about 10 yrs. The 360 only has 25 more horse than the 304, and I wouldn't want to change a flywheel for that.

 

Well, depends on what years you compare. Certainly the HP for both engines is different by about the ratio of displacement difference. So about 20% more power with the 360.

Certainly the cheapest per HP hop-up you can do to a 304 is to replace it with a 360. Add a cam and better induction and the 360 will be way ahead - it has better heads and a more favorable bore:stroke ratio. And the 304 is a rarity compared to the 360 today - there are a lot more 360s out there than 304s.

The 304 is no slouch. It has good performance for its displacement and its age. But you can do much better by going newer or bigger.

 

Agree with tim about hopping up the 360 over the 304. displacement rules when building power.