AMC Engine 258 Push Rod Length Listing per year of manufacture
Sorry it took me a little bit to put this together. I am going to ask Admin to make this a stick or Tech Article.
Hope it helps,
Push Rod length seems to vary all over the place when I purchased them for 1978 CJ7 with 258. I found the year of AMC Engine and the vendor you get the push rod from can make a huge difference in length. Wrong length can cause engine failure or poor operation.
Every push rod length was different and they did not have much to offer. Examples: Red Rooster 9.622 & 9.594”, ORiley 9.622”, Checker none, Napa 9.65”, CarQuest 9.594”. These are the offering for my 1978 Engine and some too long or short.
I was able to get a photo copies of a few pages that list the years and length and the part numbers. The pages were from an old Melling Parts Book. Pioneer Inc, 601-483-5211, Meridian, MS, was the company that had the correct information and the correct push rods. They were very helpful.
The copies I have are very poor so I cannot post them.
The Engine Remanufacture installed incorrect push rods and caused a total engine failure so this does happen. The Push Rods were too long by, .12”, a lot considering lifters can take up .030” of play with hydraulic oil pressure. The LONG incorrect push rods (9.62” correct vs 9.74” installed) and bent push rod, collapsed lifter. one lifter out of pocket, and oil path problem took out the #1 connect rod bearing. They sent me a set of push rods to replace the bent one and they were the correct length, 9.62. Glad I measured the push rods with a 12” digital caliper and took pictures. Engine Remanufacture tried to blame me for the engine failure claiming detonation. Money was refunded in full.
Glad I did the research it saved my but. They wanted $1000 to put the engine back together & return shipping & my warranty now void of any claims.
I am pretty sure many of us here at JeepForum have issue with push rods and may not be aware. Non Stock cams can / will affect your valve train geometry and parts used.
This information was from an old Melling Parts Listing for AMC Engines 258 or the 4.2 liter
PUSH RODS AMC 258 4.2 liter stock cam & set up
MPR-301 9.594” x 5/16 1971-1974 w/o Rocker Arm Shaft
MRP-332 9.658” x 5/16 1971-1974 w/ Rocker Arm Shaft (BB ends)
MPR-301 9.594” x 5/16 1975-1976
MPR-301 9.594” x 5/16 1977 w/ Temp Sending Unit in front of engine
MPR-333 9.622” x 5/16 1977 w/ Temp Sending Unit in rear of engine
MPR-333 9.622” x 5/16 1978-1980
MPR-353 9.700” x 5/16 1981-1988
Rocker Arms AMC 258 4.2 liter stock cam & set up
MR-812 1971-1974 use w/ engines with rocker arm shaft
MR-801 1974-1982 use w/ engines with rocker arm and individual pivots