304 knock issue

R

RWT

New member
All, I have a 73 CJ5 who is currently a summer fling only. She lives near the beach down in MA and every summer I head down to visit my parents and un-bury here from my father's garage, get a beach sticker, tinker and generally have a blast for a few weekends.

The original (64000 miles) 304 got really...ticky. Correlates to RPM. Very consistent and steady tick from what appears to be the top end. My dad had just been using whatever 10w-30 his fleet mechanic put in his work trucks. I've been told that newer oils dont have zinc in them which can accelerate the issue, which I believe this tick is.

Rotella 15w-40 and some lucas oil stabilizer have GREATLY reduced the noise. This engine loves it some Rotella...Anyways.

Question: How long till the engine blows up? Very general question I know. I dont wheel this Jeep. I dont beat on it. It gets the oil changed twice a summer.

Honestly Im just going to drive it until it does blow up but Im curious as to what more experienced minds have to say on the subject.

Thanks in advance.
 

Attachments

  • IMG_0281.JPG
    IMG_0281.JPG
    176.4 KB · Views: 77
Jaybird 11

Jaybird 11

Caught the Bug
Id pull the valve covers and see if it has a bent push rod or broke rocker arm. Thats a pretty easy fix. Next id run it at idle with the valve covers off and make sure all of the rocker arms are moving up and down. If some domt move as much as the others you prob have a cam shaft going flat.

Sent from my SM-G920V using WAYALIFE mobile app
 
R

RWT

New member
Yup. Nothing obviously bent. No obvious damage after pulling the covers a few years back. Actually all looked to be clean and in decent condition considering its age.
 
R

RWT

New member
Apologies, first post was choppy as hell.

This is likely a worn cam/lifter noise. I think that. The fleet mechanic thinks that. A Rover guy who used to work on my series thinks that. I just have no idea "how long" I can expect a 304 to "last" with a minor/moderate worn cam which seems to settle considerably with rotella and some lucas. This is the first AMC 304 V8 I've messed with.

Again, appreciate the input.
 
AZ Explorer

AZ Explorer

Caught the Bug
I don't think it's going to last much more than another hundred miles. The only real solution is to ship it to me and relieve yourself of the burden of a bad motor. You can use the $50.00 I'll give you to put down on something newer. These old Jeeps aren't worth much anyhow. No need to thank me, I'm a giver and am just glad to help. ;)
 
AZ Explorer

AZ Explorer

Caught the Bug
RWT said:
Ha. Already had a TJ, have a JK...like the CJ a hell of a lot better.
Click to expand...

It was worth a shot, LOL. Getting a CJ5 myself when the JK is paid off but that is still a few years off. In your case, I don't think replacing a cam is all that expensive even with labor. I had a mechanic who did one several years ago as a side job for about $600 and that included parts. Maybe $800 these days? If it's a thousand or less, I would just fix it.
 
R

RWT

New member
That is the big debate my friend. The engine, and the entire Jeep, is very original right now. If I dig into it for a cam (from experience with other vehicles) it will likely be like opening pandoras box. Then I mind as well start pulling it all apart...body off, paint, new everything...etc.
 
FallonJeeper

FallonJeeper

New member
Well,
it probably won't blow the engine. If it's a worn lifter/cam lobe, it will wear until the valve no longer opens. You'll then have a dead cylinder. It will still run, but on only 7 cylinders. That's when you spend $500 and get a new/better cam, lifters, timing chain set and all the gaskets for the front end. Spend a week-end with a couple buddies and some beer and replace the cam. Don't forget to replace the oil pump gears.

Note: I only say $500 cuz if you do it yourself, that's about all it will cost, including fluids. (for you and the Jeep).
 
holliewood61

holliewood61

New member
You would be really surprised by how tough these old engines are. I cant seem to kill my 304. I did put a cam in it several years ago, but that was just to upgrade and get a little more torque out of it. Mine has been wound out, ran hot, ran really hot, ran low on oil, and just generally abused. It keeps coming back wanting more. It makes any number of funny and what would be concerning noises if it were anything else. If you do put a cam in it do yourself a favor and upgrade. I went with a Howard's part#312481-11. Amc used notoriously lazy cams, a good cam is the best way to wake up one of these old boat anchors.

Sent from my LGLS991 using WAYALIFE mobile app
 
R

RWT

New member
^ This has been my experience so far...I literally left this vehicle in a garage for a decade at one point and it only took about an hour to get get it running again. Fairly impressive for 40+ year old technology.
 
BobNH

BobNH

Member
RWT said:
All, I have a 73 CJ5 who is currently a summer fling only. She lives near the beach down in MA and every summer I head down to visit my parents and un-bury here from my father's garage, get a beach sticker, tinker and generally have a blast for a few weekends.

The original (64000 miles) 304 got really...ticky. Correlates to RPM. Very consistent and steady tick from what appears to be the top end. My dad had just been using whatever 10w-30 his fleet mechanic put in his work trucks. I've been told that newer oils dont have zinc in them which can accelerate the issue, which I believe this tick is.

Rotella 15w-40 and some lucas oil stabilizer have GREATLY reduced the noise. This engine loves it some Rotella...Anyways.

Question: How long till the engine blows up? Very general question I know. I dont wheel this Jeep. I dont beat on it. It gets the oil changed twice a summer.

Honestly Im just going to drive it until it does blow up but Im curious as to what more experienced minds have to say on the subject.

Thanks in advance.
Click to expand...
Not much to offer except that they sell zddp additives at parts stores now. I happened to notice some on the shelf last weekend. That is NH anyway, I have no idea if there are rules around where it can be sold.
Good luck, love the rig, and the Alaska plate [emoji106]

Sent from my SM-N910V using WAYALIFE mobile app
 
JeepFan

JeepFan

Hooked
Why would you drive it until it blows up? Sounds crazy to me.... AMC motors were not known for good oiling. Could be excessive valve train wear, bearings, oil pump etc... You have a cool Jeep thats worth fixing.
 
holliewood61

holliewood61

New member
JeepFan said:
Why would you drive it until it blows up? Sounds crazy to me.... AMC motors were not known for good oiling. Could be excessive valve train wear, bearings, oil pump etc... You have a cool Jeep thats worth fixing.
Click to expand...
Because 304's and 360's are stupid cheap. He could pick one up now and go through it. When his current one let go he would have one on the stand ready to go. He would be back up and going in a weekend rather than however long it would take to go through the one hes now.

Sent from my LGLS991 using WAYALIFE mobile app
 
You must log in or register to reply here.
Top Bottom