Correct push rod length for 258 / 4.2 be carefull???
MN CJ7
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- 1978 CJ7
Silver paint with black hard top on 33" radials & eagle alumium rims. Good looking ride and have done lots of work to make it look and run great.
Stock equipment is 258 carb, power brakes, power steering, hard top & hard doors (per vehicle gross weight) tilt steering wheel, big brake package with large rotars & drums, T18 Trans with low 6.4 granny gear, Dana 20 transfer, Dana 30 front axle, Dana 44HD rear axle with 3.73 gears. True Trac ft & rear.
I was around jeeps in the 70's and drove a 1973 Jeep Truck. My family had 4 jeeps at the time. We also joined a jeep club back then too. So about 6 years ago looked for a Jeep CJ and found the vehicle above.
Push Rod length seems to vary all over the place when I purchased them for 1978 CJ7 with AMC 258 i6 / 4.2l . . I found the year of AMC Engine and the vendor you get the push rod from can make a huge difference. 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
PUSH RODS AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l 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 i6 / 4.2l AMC 258 i6 / 4.2l 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
MR-740 1983-1990
yes, this is a Fred Original
Please make this a tech article... I could not find a box/switch to do it myself, thx
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
PUSH RODS AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l 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 i6 / 4.2l AMC 258 i6 / 4.2l 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
MR-740 1983-1990
yes, this is a Fred Original
Please make this a tech article... I could not find a box/switch to do it myself, thx
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