Neverending "timing" problem :P

This whole thing originally started out with me thinking it was a transmission issue after my first test drive. The first run it ran fine, then on the second I started hearing slapping noises, metal clacking metal, loss of power, and awful backfiring through the intake until it finally wouldn't run. I opened the valve covers to find that cylinder 4's exhaust rocker was loose as a goose, the nut had worked its way up. I tightened it up and did a number of back-and-forths down the driveway and within 5 minutes it was doing the same damn thing. Cylinder 4's exhaust has loosened about half-one whole thread. SO......Today I went out and replaced all of the nuts with new ones, used thread locker, used the EO-IC method for setting valve lash on *every* valve, and found that all of them seated in pretty much the same place, thread 4 of each stud.

I crank it up, everything sounds tight and I go to doing my test runs up and down the driveway. This time, it began again within 15 minutes. Some are telling me that it's possibly the cam getting some flat lobes, but that quick!?!?! With how the valves all seated the same, and that 4 thread rule keeping with what else I've read, my gut is telling me that's not it (but my gut HAS been wrong on rare occasion).

Problem most definitely NOT solved. I bought new rocker nuts, followed the EO-IC method of setting the valve lash, and used thread locker. Even though I didn't measure the rocker travel, they all appeared to move the same distance and all the nuts ended up with correct valve lash at approximately the same thread (save one whose stud has always been about 2 threads further out than the others...and that is a constant, not pulling itself out).

Other things I'm considering:

-I know the timing is slightly off, but I'll need to move the distributor around a couple teeth in order to rotate it counter-clockwise some more....the vacuum is touching the intake manifold right now, no more room. Noob question, is timing something that gets progressively worse?

-A bad timing chain is something else I considered. Isn't that something that, if it's getting slack, would start throwing the cam off and messing with the valves opening, thus resulting in the lag, loss of power, backfiring, etc? Here's a link that turned me on to that idea: http://www.ehow.co.uk/about_6100941_signs-bad-gm-timing-chain.html

-I don't currently have the draft tube hooked up to the PCV valve on the carb, but didn't think that would start giving me hell....the draft tube is currently not plugged, either.

-Thought about a clogged oil filter, resulting in low oil pressure, but I replaced the oil and filter a few months ago, and the car *just* had it's first go round the block. Nothing but test fires in that interim time period. However, could it be low oil pressure?

The problem is really strange. My fear is the cam, but somehow I just feel it's something else. Any ideas, thoughts, opinions grounded in personal experience?

ADDED: Also of note, I had a problem with separated fuel about a month ago. The carb was actually spitting up water, emptied the tank as best I could, dropped one bottle of HEET in there along with supreme gasoline, seemed like it solved the problem. Perhaps the orange goop sh*t from the separated gas is still giving it hell?

 

If the rockers are becoming loose after you now have new nuts on them, and after being adjusted they start rattling again, it's really not likely all of the lifters are bad, so I would suspect reduced oil supply to the lifters where they aren't staying pumped up. How's the oil pressure?

 

Question. Are the same number of threads showing above the nut in the before and after scenarios? If yes, bad news, the cam is going round. This is assuming that the rocker stud is not coming out of the head, assuming, bad word, these are stud mounted rockers. Other than a bent and continually bending push rod, these are the only two things that will cause one valve to lose its clearance.
Art

 

Well for starters, it would help to know the make and model of engine, solid or hydraulic lifters and any other modifications made to the engine.

Definitely try to get the distributor installed correctly and rewire the cap if needed just to make life easier for yourself. Contrary to a lot of opinions you'll read here, it isn't about being anal, it's about knowing how to do the job the right way.

 

The first time around, the nut on cylinder 4's exhaust valve was backing off. I found that several of them weren't holding. I'm not really hearing the rocker knock anymore, but there's still a metal slap and knock when I the gas. Doesn't sound like the rockers at this point.

Same number of threads, but as I said, they're still seated and tight when I go to readjust them at their correct EO-IC positions. No slop in them. Plus, I'm not hearing multiple types of metal slap anymore, the rocker noise isn't there I've figured out....it's more of a heavy thump/slapping sound in between the backfiring through the intake

SORRY Man...can't believe I neglected that. Must be coming back in from the mad heat outside. It's a 283, bone stock, never rebuilt other than changing out all the gaskets. Hydraulic lifters. I had to hone cylinder 6 when I found a family of dirt dobbers had nested in there, causing some minor corrosion, but no major pitting. It has very minimal blow-by, no smoke.

I can get it cranked, but will only stay running above 2000rpm. At that point, it's running about 40psi. 3000rpm about 47psi. It's not able to idle at this point.

I don't believe the timing is off by much, and it's strange that I'll have instances where I can start it up fine and run it briefly, then ker-put Prior to this point, where I can only keep it running above 2000rpm, I was able to keep it idling fine, but wasn't able to get up and go, as stated in the OP. It's like chasing a damn ghost.

 

Crank it up with the valve covers off and if all the pushrods are spinning the cam is most likely OK. Good lifters on a good cam lobe (flat tappet) will spin as it operates and that will spin the pushrod.
A set of "rocker stoppers" will keep the mess to a minumum.
Dave

 

I had a simular problem on a 260 mercury motor. I checked out my timing, vacuum and timing chain. I even had a local guy from the HAMB come over and try to diagnos it!! I even put on a different intake and carb and ignition!!

Turns out I should of done a compression check at the start. Bad news!!

After I got back the crappy news of bad compression in a few cylinders I pulled the heads... I had two large chunks missing from two different valves and two pistons had holes in them.

It would start up and run, but a few drives down the street and it ran like junk and was hard to start again. I had no idea that the pistons and valves were that bad!!

Gave me all kinds of syptoms of either bad timing, rounded lobes or vacuum leaks, never gave the internals a thought.

You may just try a compression test, and hopefully it checks out ok and its something less expensive!

 

I chased a similar problem on a 283. Had a stuck lifter wiped out the cam. Exhaust lobe worn almost completely round.

 

Based on the method I used, the pushrods will not spin. Once you get to zero lash, you tighten it 1/2-3/4 of a turn (varies, some ppl say 1/4-1 full turn) and it's set. It's the stock cam, not sure if that's a "flat tappet" or not. Are you referring to it being able to spin between open and close? That would be the only possible time where enough slack might be present for it to spin.

Haven't checked the timing chain yet, was curious to see if anyone else *with* a bad one had similar problems. I've already had the heads off when I honed cylinder 6. The piston had some pitting around the edge, near the cylinder wall, but the seal looked fine. All valves/cylinders/pistons looked ok. Compression is at 15, but bobs a little....I'm currently placing that on the fact that the timing is off some from what I can tell.

One other thing of interest, at TDC, the timing mark on the balancer is about 10 degrees past the tab. We double checked it at the time, and sure enough, it *was* TDC....which we found really odd. If the timing chain was jumping or had slack and was jumping teeth, would that move the mark like that/potentially cause these problems?

 

It's easy to imagine that you might be fighting a couple different issues here from the sound of it.

Considering the age of the motor and the fact that it's a 283 that likely has over 100,000 miles on it, it wouldn't be surprising if it needed a new timing chain and gears. The cam sprocket is probably plastic and they weren't known for their longevity. The stock cams were a little soft too. Not unheard of to see excessive wear at 60,000 to 80,000 miles. Stock valve springs would go soft as well.

If you haven't already, try adjusting the valve lash with the engine running. Slowly tighten the nut till the tapping stops and then slowly add another 1/4 or 1/2 turn. If needed, start by backing the adjustment out till you just start to hear it tapping then start adjusting it down.

If it was mine I think I'd be pulling the intake manifold. Pull the pushrods and make sure they're straight and not plugged up. Then pull the lifters one at a time, making sure they move and turn freely in their bores. Check the face of the lifters and make sure they're not worn concave. Then turn rhe crank by hand while watching the cam to check for timing chain and gear wear.

If this thing sat long enough for the mud daubers to move in I can imagine it being pretty well sludged and vanished up. Maybe the problems you're fighting are why the previous owner just left it parked.

 

worn chain can't move the mark on the front damper.

If you have good feel...you can check chain slop by grabbing the fan to rock the motor back and forth. If you know what to feel for ...slop.


but won't idle below 2k? sounds like big vacuum leaks or big carb problem...IF all the basics are good, like points cond wires cap etc.

 

Other than that one cylinder, the rest of them looked ok...worn, but ok to my eyes. The previous owner is a neighbor who I trust...at least for now. They pulled it to drop in a modified 350/350 combo I'm not opposed to the idea that there was an underlying problem that they may not have realized, or that it's something completely dumb and simple. No two times that I test it are constant, at least not that I can tell....which makes it so frustrating. Now it seems like there *may* be a heat element to it. It'll get bad after driving it under light load for 10 minutes or so....then let it cool, try it the next day, rinse repeat. Another member, Miller, had a very similar problem, found out that once the coil heated up he couldn't get it above idle...*very* similar to me. That's on the list for tomorrow under "Easy fixes".....but I'm prepared for Murphy to win this one

No slop in movement. Carb is brand spankin new. No vacuum leaks detected. I have just noticed that there may be a heat component to it as I mentioned in the reply above your quote. It has idled below 2k, and that was actually where it was running best until it gets warmed up and takes a crap on me

 

I keep coming back to the fact that you know the timing is not right, but you are looking for other problems. Start with the basics, if you need to pull the dizzy, pull it, correct the mark on the balancer if you have not already, and set the timing with a light. If that does not cure it, pull the plugs and run a compression check, if good then you know you can fix it. Take things one at a time until you find the problem.

 

Like Commish says; Get the timing right, then work on the other problems;
Not bustin' your balls, This is just a rant in general not directed at you; just want to point out that I hear people talking about setting the timing right, then changing it to "make it sound better". That motor, ANY MOTOR, will run better with the timing set where it's supposed to be. After set where it's supposed to be, leave it there. After that, if it won't idle, it AIN'T THE TIMING!

Back there somewhere you ask about the pushrods rotating; When the motor is running the pushords are supposed to rotate. With the covers off watch them and see.

Don't count the threads on the rocker bolts. With it running back each one off until it clicks, then trun it down a turn and a half. After they're all set it will run better. Then go back and check each one again.................If after that, one starts clicking again its a bent pushrod or a bad lifter that won't stay pumped.

 

I think you have the rockers down too tight. As stated above, set them running. Try 1/4 turn after the tap goes away, the old lifters might be worn enough that they won't collapse enough any more. Or just full of crud!
BTW, are you SURE it has juice lifters? A lot can happen in half a century!

 

Like R Pope says, if that's suspect, explore it. If it's got solids, the very instant you run it down and it stops clicking, any more will result in the valve staying open a bit, which will be obvious.
If that proves them to be hydraulics, Run each down untill the motor shimmys, which means the valve isn't closing all the way, then back it off a turn and a half. See what happens.

Should you have them all down too tight, that would fit your symptoms, like a glove!!

 

Get the distributor in the engine correctly first. You should be able to advance and retard the timing without the vac adv hitting anything. Fix that problem and then set the timing. Close is not good enough if you want it to start instantly and purr like a kitten.

 

Yeah, that's the sme thing I was thinking. Really it's the only thing that makes sense with the warming up issue. Loosen all the rockers (in the correct order) until you can just feel the pushrod wiggle, then run it. If the backfiring goes away, lash the valves as solids and see what happens.

 

You mentioned cam. and you thought it would not wipe that fast. Cam lobes wipe in seconds. Once conditions are right or should we say wrong only a few revolutions at the condition are neeed to start it eating away and after that there is no hope for it. Cant be sure from here but it sounds like it . Lifter adjustment constantly changing. Pulling each lifter indiviually will soon tell you. When you fin a bad one you wont need to ask anyone. it will be obviuos. You four thread lifter adjustment rule is crap. Adjust them properly. They can be adjusted before the engine ever fires. in fact in the engine busines we always set them in shop.
Don

 

If you read through all of my posts, you would see that it was only used as a rule of corroboration, not specification. I *did* adjust them properly, EO-IC method:

http://www.chevyhiperformance.com/techarticles/148_0303_setting_valves_info/index.html

I've got a list of things, now...beginning with getting the timing assuredly correct, clogged fuel filter, bad coil (per Miller's experience). I'll report back once I've tried those. Saving the bad cam thing till last

 

Dude I'm sorry you're havin so much trouble with this thing. All the stuff these guys pointed out in this thread is accurate. I really don't have anything else to suggest. Just try to resolve all the basics first. Starting with the timing. I'm sure you'll figure it out.

 

Why are you so set against checking a possible valvetrain problem? When in fact the failure will be pretty obvious.

 

My buddy built a motor at his neighbors house. He fired it up to break it in. The next door neighbor ragged that it was too loud. My friend got pissed and lit the tires down the street.
Cool at the time... but cost him three (3) rounded lobes in as many of seconds!

Not saying youre breaking in a new cam, but lobes can round out in NO time.

(And, yes... my friend felt like a complete idiot 5 minutes after the smoke cleared.)

 

I did the distributor adjustment, picking it up enough to get it off the teeth so I could rotate it, set it down, and get some more adjustment slack out of it....WOW-WEE. I didn't think it was *that* off by some of the other guys' Youtube videos on here, based on sound alone, but geez....it went from running what turned out to be rough to purring almost immediately. It was b/t 10-20 degrees off *after* I rotated it back a few teeth.

At the moment, all I have is some slack/chatter in the rear valves. I can't really tell if it's getting worse as I run it, or if I'm just noticing it more over time b/c I'm listening for it. I tried, like a numbnuts, to lay down towels and adjust the valves without the covers.....and I got spooged on like there's no tomorrow Apparently the EO-IC method, when not running, isn't enough to get it set right.....like another poster had mentioned...hence my attempt. I'm going to grab some el cheapo covers from wherever and cut the tops off so I can get it adjusted while running. There's almost no chatter at idle, but rather when I put it under load...which makes sense, I reckon.

I'm not set against checking any valve train problems, much to the contrary. I just wanted to go through the lesser possibilities before assuming the worst and tearing it apart. Who wants to pull the cam when it could be a conglomeration of other, more minor factors adding up to what's happening? My only point was that a lot of people's first reaction is to assume the worst, instead of methodically offering up possible simpler, less catastrophic remedies. Who knows...may *still* end up being the cam, but if it is, I'm going to pay someone to do it. I'm a freelancer at my profession, and if it's something that bad, my time is worth more doing work to pay for someone fixing that as opposed to doing it myself. This economy isn't getting any better, so I figure I should take advantage of the work I have available to me while I can, ya know?

 

In a phrase; You set the timing. Adjusting the rockers with it idling is the easiest way, even if it gets a little oil on things.

 

Awesome man. Looks like you're on the right track.

 

This is more how it felt:

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Alternate question. Is it dangerous to use modern oil in my 283? I've read about how there's no longer any phosphorus or zinc in modern oil, contributing to the death of cams.

 

Both fuel and ignition problems can come and go and be frustrating to chase down. But the fact that it doesn't seem to want to hold valve adjustment is what keeps me leaning toward something mechanical.

If lifters are varnished up enough and stick in their bores you'll never get them adjusted right. If they're not rotating all the time you may have some wear issues you're fighting. If the plunger and valves inside the lifter are sticking they won't pump up properly. If it's got some soft valve springs and a couple stick valves they may not be closing and seating properly. This could explain your backfiring.

There's nothing inherently wrong with a 283 or other SBCs, but most motors of this vintage didn't just breeze past 100K miles, like many modern engines do, without showing some wear . Especially if they didn't get at least minimum maintenance.

Don't know what you've got for a camera but I wonder if it might help to see, and more importantly hear, just what it is you're fighting. Even a short 30 second low resolution clip might be a big help.

EDIT: Well while I was typing this I see that you've posted that you've at least found and fixed some of the problems. Glad to see that you've stuck with it and it paid off for you!

 

Yeah, I don't doubt any of what you're saying. Being my first build, I didn't even know what else to look for or check when I had the heads off honing cylinder 6 last fall. I think there's definitely some compression issues there, as it idles kinda funny even though it's *much* better than it was this morning. The only two valves that have any chatter are the rear ones by the firewall, I'm thinking that may be because I had a tougher time getting back there and getting a little impatient. I'm going to check those out again and see if I can't get it to clear it up. In the end, I know the engine is worn and tired, but if it'll work for now and not give me too much hell, and a little fun, I'm going to stick with it for a year or two probably.

Honestly, as busy as I am with my own business, I think I might just get a crate engine from Jegs next time around (which may be on this car, if it proves I have much deeper problems). I'm not a person that likes to take years working on something, never have been. They have a nice 350 with a 4 bolt main for $1500. I could swap almost everything off of my 283 and while I'm enjoying cruising with fewer worries, take the time and do a complete rebuild on it when I didn't feel pressured to get something on the road. The thing that sucks is not having a nice car to drive, as the other is a Saturn Vue Hybrid that I got talked into by my better half.

EDIT: I *say* I adjusted the valves correctly. It was my first time doing it...ever. I just read the instructions and tried to estimate "just past open" and "halfway closed" as best as I could