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I just received my new pushrods in the mail and I was comparing them to the old ones and these new ones are slightly longer...

Here is a link to a bigger picture for more detail:
http://www.certifiablejeep.com/images/freejeep/page46/large/168_6847.jpg

It is like 1/16" to 1/8" longer for the new ones. I got them from 4wd and it covers like 81-90 years. The engine is an 82, so it definitely is in those years.

My question is, with wear on the ends, I can see losing a little length, but do these things compress over time at all?

cb
Also, I haven't mic'ed it yet, but I am not sure if they are the same diameters, I will clean one of hte rods up today and measure it.

Thanks for any info.

cb
This is something my brother had to go through with his rebuild. He got the replacements from a local shop, and they informed him that the 258 had a crazy number of different push rod lengths. He ended up taking an old one in to get it matched up. His was an '81. I know this really isn't helpful, but just as a heads up.
OK, I just dug out my TSM for 82-83 engines.

It says the length should be 9.640 - 9.660 and the diameter .312 - .315.

I will check out what the old one is and what the new ones are.

According to the specs, it is only like 1/50 of tolerance, and the new one looks to be like 1/16 to 1/8 longer then the old one.

I will check it out in a few.

cb
So, I was able to measure these


Old Ones

L 9.625
D .317

New Ones
L 9.6875
D .314

Now this was with a micrometer for the diameter, but the length I only had a metal ruler, not the best way to measure it.

According to the math, the length would be arond 21/32 to put you right in there, when I measured, I got a 9 11/16's from the ruler, it will have to be checked.

So, according to what the TSM says, the rods they shipped me are closer to what the spec says then the rods that were actually in the Jeep.

The old ones length was too short and the width was too big (but there is some crap on there, so that could make it a bit bigger).

Bottom line question.

1) Does continued hammering on these "squish" them down a bit? Say 1/16 of an inch?
2) Could it be wear around the ends from being inside the lifters and under the rockers? How much "wear" would you see after say 60,000 miles?

It looksl ike I am pretty close to the spec with the New ones that they sent. I will go out and re-measure closely with a better ruler setup. I didn't think I needed a mic to get the length, but it probably isn't a bad idea.

cb
As with any metal object, I'm sure their spec changes on a variety of factors. Abuse, material quality and general wear and tear over time. If the spec didn't change we wouldn't need to change the parts.
You have the wrong rods.

You can't use longer rods because there is no adjustment and they have 0 lash. This will burn out your valves 'if' you can even get enough compression to start it.
OK, if I have the wrong ones and 4wd doesn't have the right ones, anyone know where I can get the correct ones?

cb
OK, if I have the wrong ones and 4wd doesn't have the right ones, anyone know where I can get the correct ones?

cb

Around here the local engine rebuilders will grab me any odd part or over/under bearing I want. They don't seem to have a supply issue for the 258. They do like to have the old part in their hands to verify it sometimes though, especially one like yours.
I read somewhere in a service bulletin that there are new .070" longer pushrods to be used on the 258. I belieive this was for 1981 to 1986. I'll continue to look.
I hope this works, it's from S&S engines.


Pushrod Problems On
1981-82 Chrysler (AMC & Jeep) 4.2L (258 CID) 6 Cyl. Engines

Pushrods in some 1981-82 Chrysler (AMC & Jeep) 4.2L (258 CID) 6 cyl. engines built prior to May, 1982, may disengage from the rocker arms causing noise, backfire or a miss.

To correct this problem, install a complete set of .070 longer replacement pushrods if any of the original parts become disengaged or bent.

The original pushrods are 9.640 to 9.660 long. (Part No.3227329)
Replacement pushrods are 9.710 to 9.730 long. (Part No.3242395)

NOTE: The original shorter pushrods (Part No. 3227329) are stillrecommended for use in 1980 and prior Chrysler (AMC & Jeep) 4.2L (258 CID) engines.

The AERA Technical Committee
How nice it is to have an engine in the years with the issue... LOL.

OK, according to the part numbers, I ordered MPR353 from 4wd.com.

I got a bag that said rugged ridge on it, and when you go to that website, you get to the omix-ada site.

The numbers for their site are

17410.04 Omix-ada
3242395 Rugged Ridge

The Rugged Ridge number is the one you listed, so that makes me feel at least a little better as seems to be that .070 longer like they recommend.

I will double check the measurements and the part numbers to see what is up.

Thanks for that S&S info, their website is pretty good.

http://www.rebuiltautoengines.com/jeep-cj7-articles.html

cb
Carefull on this subject of PUSH RODS & LENGHT.

258 4.2 liter from a melling book photocopy

MPR-301 71-74 w/oRocker arm Shaft 9.594" 5/16 H&H ends
MPR-332 71-74 w/ Rocker arm Shaft 9.656" 5/16 B&B
MPR-301 75-76
MPR-301 77 w/temp sending unit in front of eng
MPR-333 77 w/temp sending unit in rear of eng 9.622" 5/16 H&H
MPR-333 78-80
MPR-353 81-88 9.7 5/16 H&H

The Hydrolic Lifter, JB-2001, will take up about .030 or so play and wear. Wear is push rod, rocker arm surfaces, valve stem top, top & bottom of lifter. I agree with Mike Romain and be carefull putting in longer PushRods if the engine ran ok prior. When engine builder are using longer push rods they may not be replacing rocker arms and valves and using this to take up the extra wear. They will also be hand fitting the "Lash" or the amount of play in the valve train before the lifters are pumped up.

I have this information because an ENGINE BUILDER sent me a 1979 258 with the 9.7" rods and should have the 9.62 rods. It ran but had lifter and valve train noise from minute one. At 400 miles I had a rod bend intake #4, collasped lifter exhaust #4, the #4 failure caused a #1 failure of the connect rod bearing and piston. The engine builder told me it was detonation twice. Lucky For Me, I TOOK PICTURES OF THE FAILURES AND HAVE MOTOR HEAD FRIENDS & NEIGHBORS. My money was refunded. The funny part when I was sent replacement push rods to see if I could get the engine running they sent me 9.62". The difference of .080" is a lot, remember the lifters take up .030 approx of wear. If rockers are too long the lifters cannot pump up, you can bottom out the springs, keep valves open, and bend push rods

This is tough subject even for the pros. I would use the stock length if you have good experience with the engine running years prior. Replace rocker, bridge&pivots, rods, lifters and call it good.

Be carefull with this subject of Push Rod Replacement. I also ck with my local AUTO SUPPLY STORES about 7 of them. They all had differendt lenght push rods for the same 258 engine year.

Maybe one of the JEEPFORUM GUYS that really know their stuff can chime in. Your post is silent on the subject, but if doing more eng work like resurface the head, surface work on engine, or valves recut all that can take up more valve train play. You should post more about that also.

Regards,
Fred
Those are very good points. A good machine shop would set the valve installed height at factory specs, but some wouldn't care and allow the lifter to adjust the clearance. Resurfacing the head should also be taken in to the equation. I know Clifford sells shorter pushrods for resurfaced heads. At least for their performance heads.
I remember there was a spec. somewhere about the distance the lifter plunger should be below the retainer, but this would be very hard to check. The lifters are too far down in the block.
OK, I realize now I didn't put a lot of info in here.

I got the motor for free, tore it down and had it machined.
The block is .30 over and the mains are .20 and the rods are .10

I ordered up a set of pushrods for this before I had the machine work done, this way I would have them so I could just put it all together at the same time.

I was told the motor was an 83, but when I took it apart, I found it to be an 82, this is why a new set of rockers are on the way because one set covers 74-82 and the other 83 and up... I got the 83's unfortunately.

Anyway, I just happened to check the pushrods and all this came up. I never heard the motor run, although I was told it ran "fine".

When I took it apart, there was so much sludge in the pan and varnish in the timing cover, I am not sure that this thing had run in the past 4-5 years. The head was shot as well.

So, with all my new parts back from the machine shop yesterday, I proceeded to clean the rest of the block/head and paint it... that was the easy part... I had some paint left over from my 304 rebuild.

http://www.certifiablejeep.com/images/freejeep/page46/large/168_6853.jpg

I have never done this before and this was my first attempt, so I don't know a whole lot about the whole process. I thought by ordering the parts I would be OK, but it seems that 82-83 engines had some issues with the rods being too short. I agree that if they are too long, then that is going to cause a whole host of other issues, but with this being 0 lash, I just want to make sure all the parts are going to work.

I have the TSM for the 82-83 year and it doesn't say anything except for what I wrote earilier on the lengths. It seems that the S&S say it has been updated and the part numbers on the rods I got seem to confirm that... they seem to think the longer ones are the way to go.

cb
I'm no expert, but could'nt you install one and tell if the length would work by where the rocker rests on the valve?
I'm no expert, but could'nt you install one and tell if the length would work by where the rocker rests on the valve?

The distance from Rocker Arm to the top of valve stem is LASH and needs to be a certain amount clearance or open I do not know what this amount is. This is an art kinda and you might want to ck with local NAPA or one of the engine builders local to you. Maybe they will adjust your lash for you???

Regards,
Fred
The distance from Rocker Arm to the top of valve stem is LASH and needs to be a certain amount clearance or open I do not know what this amount is. This is an art kinda and you might want to ck with local NAPA or one of the engine builders local to you. Maybe they will adjust your lash for you???

Regards,
Fred

They are 0 lash. The rod should be able to spin I believe.
Here's a link to crane cams lifter adjustment page. http://www.cranecams.com/pdf/151g.pdf
It says there should be .020 to .060 lifter preload. I would use a dial indicator on the pushrod end of the rocker arm after all the clearance is taken up and then slowly start tightening the rocker arm and see if the push rod drops between .020 to.060. Using the pushrods you have right now.
I am so glad this post came up because I now have many questions and need to do more research. I have a late 81' 4.2 block and I just got the 4.0 cylinderhead in today. Casting number 7120.

The specs for the cam:

Part Number 68-231-4
Engine 1964-1997 General Motors
199ci-258ci
6cyl.
Grind Number A58 X4 250H-11
Description

Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.462 0.485
Duration At 0.006 Tappet Lift 250 258

Valve Timing At 0.05
Open Close
Intake -4 30
Exhaust 42 -8

These Specs Are For The Cam Installed At 107 Intake CL
Intake Exhaust
Duration At 0.05 206 214
Lobe Lift 0.289 0.303
Lobe Separation 111
Engine 1964-1997 General Motors
199ci-258ci
6cyl.
Grind Number A58 X4 250H-11
Description



I am just curious why you would use a cam for a GM engine instead of a cam for an AMC engine?
I am just curious why you would use a cam for a GM engine instead of a cam for an AMC engine?

I just got off the phone with their tech guys and the "General Motors" is a misprint on the comp cam web site. Now I need to determine the push rods I need for this set-up.
I just got off the phone with their tech guys and the "General Motors" is a misprint on the comp cam web site. Now I need to determine the push rods I need for this set-up.

I would carefully measure the ones that came out and buy ones either the same or the next increment up if none match.

That cam and lifter set gives you some 'adjustment' or 'wiggle room' doesn't it? Someone posted about a 0.040 window you have to play with.