I think my 304 is sick

I think my 304 is sick

spikey

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Location
Portland, oregon
Vehicle(s)
1978 CJ-7
78 CJ7 304, th400, Quadratrac.

I'll tell the whole story of whats going on so I hope I don't bore you away.

About a month ago I went camping the trip was 177 miles each way. My Jeep has ran great since I bought it in March. I made the trip to camp with no problems, but on the way back about 45 miles from home it started running a little strange. It was surging a little and didn't have all of it's power. I pulled over and checked my fluids then limped it home.

A buddie of mine said that the surging could be due to plugs, wires, or timing. So I bought new cap, rotor, and wires "all msd". When I took off the cap I saw that both springs were broken inside and I was running in full advance. I finished the tune up and timing and she was running good again.

Two weeks ago on my way home from work I had a Prius decide to cut in front of me then slow below the speed limit on the highway.. Of course since it's a Prius I was like "Hell no!" switched lanes and stomped on the pedal. Who doesn't love the sound of their v8? Well instead of passing said Prius I got a backfire through the carb then rattling and surging.. I took the next exit and looked for a parking lot. By the time I got it parked the rattling had stopped. When I got it home I put the timing light on it and had to reset the timing. After that it ran ok. It was running good but before it warmed up it would backfire through the carb as I was going down the street.. Kinda like it was farting.

I'm almost done, I just want to make sure you get the full picture.

Last night I had a thought that maybe the vacuum advance isn't working right so I figured I would give it a little extra gas and see if it knocks my timing out again, then get home and put on the vacuum gauge. So leaving a light not far from home I give her extra gas and got the backfire and rattle.

Problem is the rattle is really bad. I let it sit over night as I forgot about plans with wifey. This morning I started it to put the vac. gauge on and it sounds like bad rod knock to me. but I am a self taught Jeep fixer :D so I came here for a few thoughts. If you would like to hear it I will put in a link to a youtube vid I made for this post.


I'm sorry about the long post and will be very grateful for any help
I think i broke it - YouTube

Thanx for your time
Spike
 
symptoms beforehand made it seem like a timing problem turned into a bent intake valve, except that wouldn't come and go, and after watching the video it sounds too fast to be a single valve, and i doubt they would all go at once.

check the timing again. try to stethoscope the rattle and find out where it's coming from.

a "rod" knock is highly unlikely since the timing has no effect on the bottom end. how's your oil pressure? could be two unrelated problems cropping up at the same time.
 
Ya know, i didn't look at the oil pressure gauge. I should know better since I'm a crane operator..

I took the valve covers off last night to see if something had come loose. Everything in there is normal

I know i got laughed at from the guys at work when i said this but i really think that it could be my timing chain slipping. Is there any chance that my chain may have stretched and that's what's slapping?

Spike
 
It very well could be your timming chain. I had one that was so stretched that it was hitting the cover making a banging noise that I thought was something major. And it would explain your backfiring.
 
When I was in high school I had a Toyota with the 22r motor it had a ton of miles on it. That being said I wasn't easy on that little motor it saw high rpm a LOT one day it started back firing through the carb and had no power at all. Pulled the timing cover off and also the head because we thought it had bent a valve. In the end it had a broken tooth on the cam gear and the chain had streched enough to cause it to "jump" a tooth. We never checked the timing before the pull apart so I can't help you there.
 
Mtnwhlr you beat me to it :D
 
The fact that your timing changed after setting it could be explained by a timing chain issue.
 
Ok I remember hearing in the past that you can check your timing chain by removing the dist. cap and seeing if the rotor moves with the main pulley if you put a socket on it.

I just tried that I put a socket on the nut in the center of my main pulley and the rotor moves with as I turn the ratchet. Does this count out the timing chain? or is it worth taking the cover off and taking a look?
 
Ok I remember hearing in the past that you can check your timing chain by removing the dist. cap and seeing if the rotor moves with the main pulley if you put a socket on it.

I just tried that I put a socket on the nut in the center of my main pulley and the rotor moves with as I turn the ratchet. Does this count out the timing chain? or is it worth taking the cover off and taking a look?

I think I would remove the cover and check the timing chain. I listened to your video, I would start digging deeper. That is a good place to start.
 
Thanx guys.
I have an order of my yard art stuff i do to get finished then I'll start digging. Hopefully my order will pay for jeep parts.;)

Spike
 
I've had slacked timing chains before and in my cases the sound wasn't close to the one in the video, but i wouldn't rule it out. For me it sounded like a chain being dragged across a metal surface (because that's what was happening). but that was also an entirely different engine design. I've never been inside a 304, it may not be possible for the chain to drag there like it did for me.

The chain could absolutely jump teeth if it gets loose enough. that would fit most of the symptoms. I'm not sure on the 304 but this is something a lot of people deal with on the toyota 20/22rs.

take the cover off and see what's up.

when you rev the engine, does anything but the speed of the rattle change? do any of the qualities of the sound differ? pitch, tone, volume, anything but the *interval* of the sound?

also, i wouldn't run it for anything but diagnostics until you get this sorted out. it'll probably keep getting worse until you have a major kaboom.
 
Well i decided to run a few tests before i started taking it apart. When i started it up a few hours ago the noise was gone. :confused: so i set the timing and went on my little test drive path i take after major repairs. It seemed to run fine so with the motor at operating temp i double checked the timing, and revved the motor at the Carb. One good push made it start banging again. I watched the mark with the timing gun and it was jumping around. I could also hear it changing its idle speed.

I know the po from the local parts house so i called him up. He told me that he had put in an edelbrock double roller timing chain in about a year before i bought it.
He agrees that it sounds like a timing issue so i ordered a new edelbrock set. But when i open it up tomorrow if there are no broken teeth what else could i look at or for? Could something be causing the chain to stretch that fast?

I absolutely love my cj and want to take care of out the best i can. But I'm still learning and not sure on the little things. should I change the thrust washer in case its wearing down or other little things like that.
And yea she is staying parked i don't want to nuke it.

Thanx
Spike
 
When you pull the cover look for marks on it from the chain slapping it.
 
Well its going to move, if it didn't the engine wouldn't run at all.

A common cause of surging is vacuum leaks. I would also investigate a little further around the dist. Make sure the hold down is holding it tight, no more problems with springs..etc. The fact that the problem changes from hot to cold would make me look at that before I went after the timing chain. Im guessing the rattling you are hearing is pinging or preignition. Its possible that it was so bad that you did damage the engine, but engines do make noise and if you listen close enough you can start to hear things.

Not sure if you have the VC off still, but you can put the engine up on TDC and see what the rocker is doing. When you are at TDC for any cylinder, the upcoming valve event should have a little delay. So you should be able to move the crank a few degrees either way ( I want to say like 15* but not sure) without seeing any pushrod movement.

Pulling the tcover is more of a sure way to do it though.
 
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Jason did you listen to his YouTube video? Dosnt sound like the motor is pinging. It does it from idle all the way reved up.
 
Sounds like the lifters aren't pumping up. I broke a pushrod one and it sounded the same. The lifter popped out of the lifter bore, oil no longer was pumped to the other lifters and the valves knocked. I would pull both valve covers and look for anything out of place and or loose.

BTW - the oil pressure gage is up stream from the galley so the oil pressure would still show good.
 
I pulled the valve covers Friday everything looks normal and feels nice and tight. I'm going to get the timing cover of after work tonight. If nothing else I'll know that it is or isn't the problem. The new timing chain had to be ordered so I'll be in wifeys car till then...

Spike
 
As far as it changing from hot to cold i don't really think that's the case. If this happens when I'm on the highway the noise only Lasts about 20 to 30 seconds, i just managed to make it happen when i was close to the house. I had a feeling that it would go away like it had been. That's why i got the video. It doesn't stay around.
As far as engines making nose, yea I'm a crane operator I'm trained to listen to noises anything odd and i hear it. But while we ate on the topic of noises is it common for the dist. To have a constant ticking noise? Its an msd. Its been ticking since i got the Jeep, done old guy told me its just something the 304 does..


Spike
 
EDIT: reread the thread and dauntless was way ahead of me:)

Just watched the video; wasnt available before for some reason.

From what I heard, sounds like valvetrain like CJ said. Rod knock frequency is much lower; tone is much deeper. Cant be positive from a video but thats my opinion. Unless you wiped them all out but thats unlikely.

The 22r is known for having the timing chain noise once they wear out. Totally diff. setup though with plastic guides and an oil pressure driven tensioner.

When an engine is running rough like that the idle is bouncing around and its common to see the mark moving. Id put that in the back of my mind at this point.

I would get a mechanics stethoscope and listen at different points on the engine. This will help you pinpoint the noise. Not sure if you looked really close for broken valve springs; they can be hard to spot. Id also look real hard for bent pushrods.

Another thing you can do is get another set of valve covers at the junk yard and cut the tops off and run it. A small amount of oil will come out but its not much. We used to adjust our valve train running like that. Just dont rev it up.

I'm guessing you still have the stock bolt down rockers and not aftermarket adjustable ones?

First car I bought had a valvetrain issue about 100 miles after I bought it. Guy didnt change the oil enough and it gummed up the lifters. Kindof sounded like a loud type writer. Didn't run rough though. Yours almost sounds like the valve train is getting no oil.

Does anybody know if the 304 is an interference engine?

Its possible if it is, you jumped enough teeth and bent some valves. Thing that keeps throwing me is that it is intermittant. Takes me back to the lifters; saw that you mentioned it ticked before also.
 
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