Re: 258 to 360 swap
The following is the information I collected as I ws preparing for this swap two years ago... can also be found in the tech section of shortwheelbase.com
Swapping an AMC 360 into a CJ7
1) Bell Housing:
- All AMC/Jeep V8s and all 1972 and later 258 I-6s have the same bell housing pattern and share the same mounting bases.
2) V8 Crankshafts:
- 1966-1971 cranks can be used with torqueflites using a slip-in adapter.
Most cranks are drilled for a pilot bushing, but check to be sure.
- TH400s handle just about anything you throw at it, but then I've also heard that a built 727 will handle hard downshifts better (like for mud bogging).
After 1974 (all CJ7s) the TH400 bolts to the AMC block, but a 0.040-inch spacer is needed, or the front pump will grenade.
- 904/999 OK for 304 or a mild 360... be sure to get the kick down linkage with the 360.
- 727s from wagoneers can be swapped in for bigger engines, but the clocking is slightly different and the pan is bigger. To clear the front drive shaft from hitting the transmission pan you will need to either; 1) have a lift of 4" or more, 2) install a two-piece front drive shaft, or 3) modify the pan.
- 1972-1975 T-15 3-spd will easily handle V8 power.
- 1972-1979 T-18 4-spd will easily handle V8 power.
- 1980-1986 T-176 is barely strong enough to handle 304/360 power.
- T-4, T-5, and SR5 boxes are not suitable to V8 power.
- AMC V8s are externally balanced, so use matching components for vibration dampers, flywheels, and flex plates. If your having trouble finding a 360 flywheel, a 258 flywheel can be rebalanced and used. PartsMike.com can supply new flywheels for both 360 and 401's (late style) for $139.00 and new bellhousings for $179.00 (8/02 prices).
- Up to 1979 also did not have the markings for install a slave cylinder, but 1980 - 1986 does, PartsMike.com has a kit to hydraulic.
4) Engine Mounts:
- The right chassis engine mount must be changed for a CJ piece with a 304 V8 (left mount can be retained).
- The mounting brackets on the engine must be changed to 1972-1981 CJ pieces for a 304 V8.
- Neoprene mounts must be changed as well and can be found at any local parts house (look for 1981 CJ7 with a 304 V8).
- An alternative to the above is MORE's bombproof motor mounts.
5) Cooling System:
- I6 radiator outlets match the V8's.
- If you have a I6 heavy-duty radiator (3 core) you can reuse.
- A CJ V8 fan shroud must be used, application is for a 1981 CJ7 with a 304 V8 (part No. J5355678).
- A CJ factory seven-blade clutch (viscous) fan is best... from V8 or I6 heavy duty cooling package.
- Or you can replace the mechanical fan, with an electric one, and then forget about the shroud (could be cheaper). Electric fan gives a good horsepower gain, and is less stressful on the water pump, especially if in deep-water crossings, unless the clutch is in good working order. Install a toggle switch that turns the fan off during water crossings.
6) Electrical System:
- Most of I6 wiring harness is compatible, coolant temp sensor wire must be lengthened.
- Motorcraft modules work with 6 or 8 cyl distributors.
- Ancillary mountings may need to be changed. Motorola alt. bracket can be drilled out to accept a Delco alt.
- Wired the system using the Team Rush ignition that is covered in these tech articles.
7) Power Steering:
- V8 high-pressure hose is needed (although some report that the I6 hose works fine). The high-pressure hose has a compression fitting pre-1980, and O-ring for 1980 and later. PartsMike.com has steering parts for SOA steering applications.
8) Fuel Line:
- The AMC V8 fuel line is on the driver's side while the I6's in passenger side. - A new fuel line will need to be fabricated and re-routed on the left side frame rail, or a fuel line can be pulled off of a 304 powered CJ.
9) Exhaust System:
- 1980 and up SJs (Grand Wagoneers), J10/20s have the rear dump left exhaust manifold (to clear the front driveline better). All the 1970+ V8 AMC cars, CJs and 1979 and earlier SJ/J10s/20s have the center dump left manifold. There is only one style right manifold after 1970.
- The 2 1/8 inch "Y" exhaust pipe from a 304 powered CJ will take care of the exhaust, If you can find one and it matches your exhaust manifolds.
- Use 2 1/2 inch pipe from "Y" on out.
- Try to get the manifolds with engine... especially if using earlier rectangular port heads (1966-1969).
- Hedman, among others, makes headers for AMC V8s in CJs. Headman headers that are fenderwell exit for the 304, will work on the 360, with the automatic, you pretty much have to run side pipes though.
- 1966-1969 AMC V8s have rectangular exhaust ports.
- 1970 and later engines have dog-leg exhaust ports (up to 50% better flow, but only a big gain at higher rpms).
- Intake manifolds change with change in exhaust ports 1966-1969 and 1970 and later take different intakes.
- Combustion chambers differ on earlier heads and heads must be matched to pistons to get correct compression.
- 1970-1971 have 50.60 cc (casting No. 319-6291) combustion chambers. Later heads have 57.92 cc combustion chambers.
- The AMC 258 weighs in at 440 lbs. while the AMC 360 weighs 540. Pre 1981 258s weight 90 lbs. more.
- Visually all V8 engine blocks look the same as earlier engines. This means that emissions equipment can be placed on earlier blocks and pass visual inspections.
- Use the wiring diagram for a 1980 CJ with a 304 V8, it will be correct for AMC V8 swaps.
- The Computer on later CJs can be taken out.
11) Engine Oiling:
- AMC V8s tend to starve the rear crankshaft bearings and distributor gears. The solution is to put a TIG welding tip into a oil gallery plug. TeamRush's instructions follow: Drill the left (odd) bank lifter gallery plug in the front at an angle directed at the fuel pump eccentric and the distributor gear. Tread the plug, and screw it back into the block, then screw a 0.024" mig welder tip into it. When the oil pressure is up, it sprays a continuous stream of oil on the top crankshaft gear. That oil is slung out to the timing chain, and applies a continuous supply of oil to the timing chain. When the slots in the gear pass by, (half of the gear is open) the oil stream lands on the distributor gear and fuel pump eccentric, (both of which run virtually dry other wise). The Hobart brand of mig tips are made of a better grade of brass, and have convenient flats that help in screwing it in. Entire cost of the upgrade is about $2.
- Drilling 1/8 inch holes (chamfer them) in the lifter valley next to the lifter holes will get oil to the cam lobes quicker, but I think that this step is overkill for jeepers and didn't do it to my block.
- When you rebuild the oil pump, check the clearances to make sure that they are within specs (.002 or better). Otherwise, you might be wondering why your oil pressure isn't any better than prior to the rebuild. There is an outfit out of Eugene, Oregon called FSRO (541) 461-2335 that reconditions timing covers and sells a gasket kit to achieve necessary clearance. Also, there is an aftermarket replacement timing cover out on the market.
12) Miscellaneous Information:
- The driver's side inner fender well is different between the I6 and V8 CJs. This only makes a difference if you are planning on running an AIR pump with your 360 swap.
13) Anybody with more or better info... I'd be happy to add it into my database.