Inliners International Forums General Discussion AMC/JEEP 232ci and 258ci. how do you spot the difference

Hi , can someone please tell me how to tell the difference between a 232 and a 258, thanks

If You pull the exhaust-manifold the 232 up to at least 1970 year model have large exhaust ports,the 258 has some small ports that You almost can't stick a finger trough,the 232 You can get 2 fingers ang half a foot trough with some force ;)...

And under the valve-cover You will find shaft-mounted rockers on the 232 the bigger engine has pedestal-mounted.

Be good : Speed Swede

Hmm, I dunno about that... the only difference between a 232 and 258 is the crank.

Shaft vs. rocker is a model/year issue, 199, 232, 258 all got the same heads in a given model year. Originally shaft, then moved to rockers, then back to shaft around 72? pending the result of some lawsuit regarding rocker design, then ball-socket individual rockers up through the end.

Externally, all of the ports are absolutely identical up to the 4.0 heads. Last weekend I put '83 manifolds on a 70 head, and I checked -- ports match. It lined up fine to the cleaned-up 64 head on my bench.

Even the 1990 4.0 EFI manifold will BOLT ON to the 64 head. That's the RENIX head. 91 up fits up til they revised the head and raised the ports and made them smaller (hi flow heads). And THOSE heads still bolt onto all motors back to 1964 (introduction). (AMC and Chrysler switched from 7/16 to 1/2 headbolts, so some combos you need adapter washers (available aftermarket) and some need the head holes drilled.

There were different deck heights in various years, but I think (VERIFY THIS! DONT TAKE MY WORD!!) the hydraulic lifters will compensate, I don't know if there's different length pushrods.

The AMC six is a very versatile platform for motor hackery. The 258 is like a small V8 unless you need to build to rev over 6000 for extended periods.

It's a long motor, due to the 7 main bearings. But there's a lot of adapters available due to it's use in Jeeps, so you can put pretty much ant transmission behind it, AMC, GM, Ford, Chrysler. ANd they're cheap and plentiful!

Thanks for the info although I'm still unsure about a visual ID, let's take a different route, did the 258 supersede the 232 and if so what year did that happen, or were they both available at the same time, did Jeep use the 232 or only the 258, thanks for the info that will be forthcoming!

Modern AMC sixes/years:
199 - 3.75" bore, 3.00" stroke
"short deck", 6.125" rod, 1966-1970

232 - 3.75" bore, 3.50" stroke
"short deck", 5.875" rod, 1964-1970
"tall deck", 6.125" rod, 1971-1979

258 - 3.750" bore, 3.895" stroke
"tall deck", 5.875" rod, 1971-89

242 (4.0L) - 3.875" bore, 3.440" stroke
(note that most pubs round 3.875" to 3.88")
"tall deck", 6.125" rod, 1987-2006

Only two deck heights. Tall deck is 9.528-9.534". There's a 1/8" difference between short and tall (half the rod length difference). Short should be 9.278-9.284". Tall is from a 74-76 AMC factory service manuals, prior to 74 deck height wasn't printed. Deck height changes slightly over the years - 77-82 states 9.487-9.493", 93 Jeep factory manual states 9.429-9.435". Don't know if the blocks actually vary over the years to alter compression or there are errors in the manuals.

Note that two different bell housing sizes were used. 64-71 used the "small" diameter bell as used on prior AMC/Nash sixes. Starter is on the left hand side. 72-06 used a larger diameter bell, same bolt pattern as the AMC V-8. Six cylinder bells are roughly 6" deep, V-8 bells are roughly 8" deep. Use corresponding transmission with bell to swap. 71 and earlier also use a Borg Warner auto which uses the same crank flange as stick shift models. 72+ use a custom made Chrysler Torque Flite auto trans (AMC bell housing pattern is the only difference from Chrylser models). The stick shift flywheels interchange, but the Chrsyler flexplate will only bolt to 72+ cranks. The crank flange has an indentation that aligns the flexplate.

Heads varied, but all mid 1980 and prior engines used a cast iron intake and exhaust that bolted together and 1/2" head bolts. Mid 1980 and later used an aluminum intake separate from the cast iron exhaust manifold and 7/16" head bolts through 1986. 1987 moved to a cast aluminum valve cover and back to 1/2" head bolts.

Cranks are 12 counterweight through mid 1980 (corresponds with head bolt and manifold changes), four counterweight after. There doesn't appear to be any strength differences in the cranks, though the older crank is heavier. The only noted difference is the lighter crank can spin up slightly faster (we're talking milliseconds here!) and the heavier crank has more stall resistance due to greater rotating mass. Rock crawlers make good use of the heavy crank, but breakage reports are about the same for both.

There's no way to look at any engine and tell what size it is except for the 4.0L -- it has no provision for a mechanical fuel pump. There is a code stamped on a flat on the block near the block/head parting line between cylinders #2 and #3 on the right side (spark plug side). The fourth character is the engine code.

A - 199/1V, 70
A - 258/1V, 71-79
B - 258/1V low compression (Jeep only), 71-74
C - 258/2V, 76-89
E - 232/1V, 70-79
F - 232/1V low compression (Jeep only), 71-74
G - 232/2V, 70-74
J - 199/1V, 66-69
L - 232 (1V or 2V), 64-69
MX - 242 EFI (4.0L -- Jeep only), 87-06
note: may have just "M"

The first character of the engine code is the year -- that's how you tell the 70 199 and 71-79 258 apart! From 1980 on the first character is the last digit of the year, and zero is used. Before then it's more complicated! The code started in 1959 with "1" used for 1959. Just count forward through 9, then skip zero and start over. So "1" could be 1959, 1968, or 1977. Knowing what engine sizes were built during a year and some engine details is necessary to decipher the code correctly. So code 108A15 could be a 68 199 or a 77 258. Check starter position. 68 would be on the left, 77 on the right. Clear as a bell, right??

Incidentally, the 2nd and 3rd characters are the month the engine was built, and the last two are the day of the month.

Thanks farna, that's the sort of info I was looking for , cheers