The wife and I decided to take this week off and ride the entire length of the Natchez Trace Parkway from central Mississippi to Nashville, Tennessee. We stopped and spent the night in Muscle Shoals, Alabama, then got up early this morning and headed north again on the Trace. Everything was running smooth in my 77 Vette with the original stock L48. When we got about 60 miles south of Nashville, I slowed for some traffic, and when I reaccelarated I noticed the engine was missing. I pulled over and got under the hood, looking at first for a vacuum hose off or leaking. Couldn't find any leaks so next I checked to see if it was getting fuel. It was, so then I checked to make sure my distributor was tight and timing hadn't changed. That looked good, so now I'm scratching my head. Checked the oil and it was full and looked OK. Nothing in it that shouldn't be there. I then started checking the plug wires and did find one boot that was somewhat melted and a couple of other questionable wires. Now I'm thinking I'm on the right track. We limped back to Lawrenceburg, Tennessee and found an Advance Auto parts store. I installed new plug wires, told the wife it was fixed. Let's go. Not so fast. Started it up, same thing, still missing. Go back in the store and get a set of spark plugs. Installed them(and by now my hands are pretty blistered), and still she's missing bad at idle. Now my wife and I are both scratching our heads, wondering what a tow truck will cost. We're 250 miles from the house. I said "get in", let's try it. I remembered that this problem started about 10 miles after we filled up with gas. So now we're grasping at straws, thinking we got bad gas. In my infinite wisdom, I'm thinking maybe if we can run all the bad gas out and fill it up with fresh, we'll be home free. We got back on the Trace and headed south. Actually the motor ran pretty smooth once it got up to cruising speed. Rough as could be at idle though. The gas guage hit "E" about 10 miles north of Tupelo, Miss. Nowhere to get gas except Tupelo, so we kept rolling. We finally limped into a service station in Tupelo on fumes. Gassed up and took off again. 100 miles to go yet, and she's still missing. We finally pulled in the yard about two hours ago. The temperature guage never went over 190 and the oil pressure stayed at 40 the whole time, so I'm figuring this can't be too bad. As soon as I got home I tried to check the timing but it was running too rough at idle. I just now did a compression check on the right side and I got 140-150 on 4,6,8 cylinders. Pulled the plug on number 2, put the guage in, turned it over and zilch, nothing, zero compression, and the number 2 spark plug is black. I know this can't be good. I've maintained the car well since I've had it, but it is the original motor with around 200,000 miles on it. I really can't complain, it did get us home. I figure I'm looking at rebuild or crate engine. Can someone with more engine knowledge than me explain exactly what happened to the number 2 cylinder??
Thanks,
Kenny

 

Wiped Cam ????

If it were my car I would pull all the plugs, and the valve cover. Then check to see if there is any movement at the rocker arms on the bad cylinder while turning the engine over manually.

Hopefilly others will chime in.......

 

Pull the valve cover and rotate the engine while looking at the intake and exhaust valve rockers. I suspect you have a cam lobe issue. The rocker operation should be the same at all cylinders. If a cam issue, you will see it in the lack of rocker movement.

 

Look for a stuck valve on number 2

 

a wiped cam lobe would cause the poor idling, and the running on 7 cyls. feeling, but not the cause of loss of compression. could also be a broken rocker arm or stud. a partially broken valve spring or stuck open valve, broken valve seat, burnt valve. would cause the loss of compression. i was going to say the rings, but he would have alot of smoke issues with 0 compression. but with no obvious visual mechanical problems, burnt or broken exhaust valve, 77 350 with 200K, time for O/H, just my opinion.

 

reread your story and notice you didnt mention the fuel filter. Your symptoms seem to indicate a fuel delivery problem. Certainly worth checking before an overhaul.

 

update: Just removed the valve cover and turned the motor over. Rockers appeared to be moving normally. Looked a little closer and found the problem. Broken valve spring. Two questions for you guys. Can I just replace the one broken spring, or should I replace all of them?? Also, do you think driving the car 200 miles with the broken spring damaged anything else that I can't see?? I found a few little pieces of the broken spring laying on the head. Do you think the broken pieces are confined to the top of the head where I can get them out, or could some have worked their way into the motor??? You guys are great. I was getting ready to order a crate until I read your replys on things to check. Thanks again,
Kenny

 

you're lucky you didn't drop the valve and grenade the engine. There is an attachment for an air compressor you can use to replace that spring with the head on the car. You'll need to pull back up on the retainer to get the valve to seal first then replace the spring with a 10 dollar spring compressor tool.

i wouldn't go through all the trouble to replace all the springs. Clean up the spring pieces you can find laying in the head. It there are others that fell down they'll lay in the pan and be fine. Just replace the one spring and keep going for now. Sounds like you will need a rebuild/new engine soon anyway so it doesn't make sense to put a bunch of work into it.

 

yes you can replace the one valve spring easily. but the rest of the springs may be in the same condition after 200k mi., its your decision. hopefully the piston didnt hit the valve and bend it. just depends on how far it fell down while running.
most of the spring pieces probably stayed on top of the head, any smaller pieces will probably make their way to the oil pan. where they will probably just sit next to the oil pump screen, or get caught in any oil sludge in the bottom of the pan. if it were mine, i would replace all the springs and seals, while you have the tools out. but thats just me and might as well syndrome.
turtlevette is probably right just fix the one spring, save money for rebuild later. good idea

 

I would pull the head and check the cylinder for damage. It would be a shame to replace the valve spring if there is internal damage caused by a valve banging around in the combustion chamber. If all looks good, I agree to replace just the one spring and re-assemble. Should be obvious when you pull the head.

 

Replace #2 spring using a lever type valve spring compressor (has a 12" long handle and a slotted right angle foot that fits onto the rocker stud).
To stop the valve from pushing down, bring the #2 piston to firing point (use the distributor firing position at #2 pointing the rotor at the cap terminal) and feed a 3/8" nylon rope into the spark plug hole until no more goes in, then hand turn the engine until it won't turn over. This will stop the valve from pushing down so you can remove the spring retainer, use a magnet probe to remove the keepers, then remove the spring. Remember to replace the valve stem seal and refit a spring. Use a used one off a scrap head (you are rebuilding it soon, aren't you?) Check the push rod and rocker for damage. Reverse the retainer removal procedure to re-instate, then remove the rope. Replace the #2 spark plug and fire it up, if it runs smooth your'e on a winner, if it doesn't, you've bent the valve, so it's a 50/50 thing. Could also do a compression check to get further confirmation if you wish.
Good Luck, Rod

 

Glad you got it resolved.

 

I would not pull the head on a 200k engine to check. Just replace the 1 spring and cross your fingers. Also, replace that spark plug.

 

She's back on the road. I went ahead and replaced all the valve springs. Did a compression check afterwards and it's back up to 150 on that cylinder. The other seven are 140-150. Don't know if it's my imagination, but the motor seems to idle a lot smoother than before. I'm guessing some of the other springs were weak. Doesn't appear to be any internal damage. Believe it or not, after driving it over 200 miles with that broken valve spring, the keepers stayed in place, holding the valve up. Did I get lucky or what. Running smooth, no knocks and oil pressure right at 40 psi. We drove it about 100 miles today after installing the new springs and so far so good. It never did knock, smoke or lose any oil pressure during this entire ordeal, so maybe I'm good for a few more miles. Thanks again for all the help. You guys are lifesavers.
Kenny

 

Good deal and good luck with it.

 

With 200K on the clock and a broken valve spring I'd be looking at a crate or rebuild. Why push your luck.

You might last another 100K, or 1K. You got your money's worth out of the original engine, time to put some in it.

It's a good excuse to get a nice ZZ fastburn

 

......almost the same situation here, except at idle it's purfect & under a load it breaks up. Started out like this, on my tri power set up the fuel lines were leaking, the only way i could get them all tight was to remove & replace the center carb. After replacing all 3 fuel filters, cleaning & tightening the lines i incurred the same situation you explained !!!

as i give it gas it hesitates surges & bucks, noticed it was loading up & i smelled fuel i thought maybe i got some sediment in the needle & seat so i replaced that. no more fuel smell not loading up but Still surges, bucks under load thought then maybe it was now starving for fuel so adjusted the needle & seat one more time &............still runs like CRAPOLA.........
starting now to think like the original post, fouled plugs ? points ?
SHYT....... i'm out of patience.............
ANYONE ?