I need help fast. My 258 in my 1989 YJ is dying quick. I have access to a 304 with carb, hedders, starter, flywhell and possibly a bellhousing if needed to plop in.
Seached both this site high and low as well as the net for a writeup on the swap to no avail. Only found vague bits of, " I think..." or "it should...".
I need info on the swap, engine mounts, what will fit and what won't. Overall how to do it and what to expect. I have a new triple core rad so I'll be running a an electric fan (either single or duallie). Alternator will be the 258 one for now. Not sure if my rad entrance/exit line up with the 304. Steering pump will be the stock 258 one for now. Should suffice. AX-15 is staying in place as well.
Please help as the swap will be done shortly.
Cheers
I was looking into something similar for my 89 YJ.
You can get weld in motor mounts from Advance Adapters. I have not found a bolt in swap for mounts yet.
The 304/360/401 blocks have the same bellhousing bolt pattern as the 258 so it will bolt to your AX-15 bellhousing.
I believe the clutch from the 258 will bolt to the 304 flywheel. You will need to get a pilot bushing that fits in the 304 crank. I believe the same one that you have in the 258 now will work.
So far all I have found about the exhaust is most people say use the stock manifolds instead of headers. The headers leak and are hard to fit without cutting things up.
The fuel line is on the wrong side and has to be switched to the other side.
I have yet to find a writeup on the net for this swap. If you do end up doing this swap, please do a write up so we can share info.
If you can I would try to find a 360. The 304 does not have any more low end power the the 258. 360 has a lot more and if you are going to go v8 go big . But I do not know how well you tranny will hold up. But it should bolt up to either v8 And you clutch will bolt up to the 304 flywheel. And you can take your pilot bushing out of the 258 if you need to it will fit into the 304.
For what it's worth. I put a 360 in my 88. Bought mounts from AA for 2 bills, put a edelbrock performer manifold and carb on top. I used a t-15 tranny but a buddy left his AX-15 in place and blew his within 3 weeks. He drives like me, big on the stupid pedal. I think you should seriously consider a new pilot bushing and resurface the flywheel. I didn't and got wicked chatter. In retrospect a pretty easy swap but I went the long way. Try to get a 360 or 304 steering pump, My 258 pump hated 33's, 360 spins them fine thru the yj steering box. Fuel lines are a non-issue as long as you keep them away from the manifold and use a soft line with inline filter to the carb ( but thats with the edbrk). It's worth the headache though, gobs of power and potential. If you do it get a competent welder to put in your mounts and if you sling it low enough you have room for a torker later. Exhaust is kinda a pain in the ass but get a new y pipe and run it passenger side. also use the ECU from the donor and shit can your computer if you can (smog) I'm in alaska so it don't sweat me. I am fairly inexperienced at the mods game but I did it? If you have a specific question about something pm me. hope that helped. late
I switched from a 258 in a CJ to a 304 because I found one for next to nothing. The stock 304 engine mounts bolted right up to my frame. I used the stock bellhousing and 258 clutch. I used the 304 flywheel and had to add a lockwashers to the clutch plate bolts. I don't know if the flywheel was machined too much or if it uses a different clutch and/or bolts. It has worked for some time with the lock washers and my centerforce clutch. I was already running a t-18 tranny so that was not a problem. I have had really good luck with the 304 in comparison to the 258. My jeep is older and there was always a constant intake manifold leak. I know it might have been fixed by some machine work to the cyl head and intake. I have had the 304 in place for 2 years and it runs great. I idles up stuff where the 258 used to shut down.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Pirate 4x4
18.7M posts
366.4K members
Since 2000
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!