The production connecting rods for the AMC six come in a variety of flavors. All are cast iron (although tracked by “forging” number) with a press fit piston pin. All are the same journal width and pin size. Rods are available in two lengths, 5.875” and 6.125”.
The 5.875" length was used in short deck (64 thru 66 1/2) 232 engines and all 258 engines. There are three castings:
The 6.125" long rods come in two varieties:
The Jeep 4.0L rod is the strongest of the available 6.125" rods, lighter than the 5.875" rods, and probably stronger than the 5.875" rods due to it's design and quality controls not available during production of the AMC rods.
No production 199 or 232 rods should be used for high performance applications. If a 5.875" rod is required, use forging 707 rods. If a 6.125" rod is required, use 4.0L rods.
1) early 232 (forging 154, part #3172341),
2) late 232 and early 258 (forging 707, part #3180444),
3) late 258.
The early 232 variety was replaced with the newer, heavier casting starting with engine date code 710L21, which makes them almost non-existant today.
1) 199 engines and 232 tall deck engines (forging 207, part #3173210),
2) 4.0L engines (muliple part numbers, see table below).
LENGTH
ENGINE
YEAR
PART #
FORGING#
WEIGHT (g)
5.875”
232
1964-66
3172341
154
660
232
1966-70
3180444
707
700
258
1971-81
3180444
707
700
258
1982-88
3237812
unknown
unknown
6.125”
199
1964-70
3173210
207
660
232
1971-79
3173210
207
660
4.0L
1987-95
53020126
544
660
CONNECTING ROD PREPARATION
Rod preparation should be the same as that used for any production type connecting rod used in a performance application. Beams should be smoothed and polished, balance pads should be minimized, and rods should be shotpeened professionally. Rods should be resized by a competent machine shop, not a rod rebuilder. Rods rebuilt by these mass quantity rebuilders are of the poorest quality and will fail under racing abuse. Angle cutting the cap parting surfaces is not to be allowed - they should be cut flat and parallel prior to big-end resizing. The pin end may be bushed for full floating pins with the addition of a chamfered oil hole on the top of the rod and a radiused chamfer on the bushing itself in the vicinity of the oil hole to aid in spreading the oil across the pin. The bushings typically used in Chevrolet rods may be used (similar pin diameter). Rod bolts should be replaced with high strength units similar to those manufactured by ARP. My race prepped 4.0L rods weigh in at 625 grams after balance pad lightening, beam polishing and shot peening, bushing the pin end, and installing ARP bolts.