LannyL81

This is on my 81; getting a knock and difficult to keep running. Coming from passenger side....pullled valve cover and all looks fine...but have not rotated engine and watched valve train yet.

Last summer I noticed I had a knock that just seemed to be a noisy lifter...slow to pump-up...but always did. Now this knock sound is there all the time and gets much louder when engine is rev'ed.

Can a lifter fail to the point of not working at all? Or it is more likely that I have spun a rod bearing? Engine only has about 8k miles on it.

UPDATE 4/9
Found #4 exhaust valve is not closing. Spring is sitting about 1/8" lower. Do not know why yet.
See pictures at last posting.

Indiancreek

What's your oil pressure? Any drop? Put a timing light on it and see if the knock matches the light flash. You can move the light hook up to different plugs and you can probably determine what cylinder. The crank and cam travel at different speeds.
If you can get a long screwdriver or a solid metal object against the pan rail whils it's running, from underneath if you can, Be carfull as long metal objects and fans and belts don't get along, listen to the panrail for a knock.
Spun bearings are fairly obvious, but it's the last one most people want to believe, as it ends up costing more.

damoroso

Lifters and rod/main bearing knocks are usually two very different sounds. The lifter is usually a "tick" unless it collapses completely. Then it gets more like a "clak" but you'll also notice then engine running very rough because one of the valves won't be opening if that happens. These sounds usually sound like they're from up on top of the engine. A rod or main bearing will cause a knock you'll hear down lower in the engine and usually won't change sound except getting faster as the engine revs.

L88Plus

Pull one plug wire at a time to try to find a rod knock - it'll go away or get much, much quieter when you pull the correct plug and there's no combustion event to hammer it down against the crank.

ajrothm

+1

What he ^^^ said.

BPHORSEGUY

78 C3 Light Corvette Blue

I am so sorry. Sounds like a rod. Oie pressure?????????

dochorsepower

More information needed. You say engine only has 8K miles on it, was it rebuilt? what was done? This same comment applies to many OP's on this forum, how can someone help if we don't have enough information to diagnose. Some initial thoughts, cam may be eating itself. If you have a rebuilt engine with a performance cam and don't use a zinc wear additive, cam and lifter wear can be a problem. A crankshaft bearing problem usually sound like a dull thud rather than a clicking ar tapping sound.

...Roger...

Use your heat gun on the exhaust manifold,if the cylinder is dead you'll see it.

Oldguard 7

Which end of the plug wire? If you pull the plug wire from the spark plug, you will get burned (especially if you have headers) and if you pull it from the dizzy, you will get your bones rattled from the electromagnetic field? So the question is how would you pull it from the dizzy end (which is easier to do) without getting zapped?

LannyL81

Oil pressure is good.

Ran the engine for 20 seconds and then felt each header tube.....found that cylindes 4, 6, 7 were not as hot as the others.
Pulled the plug on #7....wet with fuel.

Going to check spark on those cylinders, but will need wife's help for that....and that will be tomorrow.

Perhaps my ignition module or coil is failing and is not able to provide the spark to all cylinders..???

LannyL81

TTT
updated #1

...Roger...

When someone says timing jumped a tooth,that usually means the timing chain jumped a tooth due to a worn out cam gear.
Did your timing chain jump a tooth or did you mean something else ?

Indiancreek

You are a long way from here, but if I can help let me know. See what is usable with your parts. If the valves are bent and the pistons don't have a sunroof, timing gear and head repair may do most of it.
If you want to send them here, I'll mag them and check your guides. Maybe all the valves may not be bent.
If original GM valves are good enough for you, I may have enough laying around here you can have.
There will be other things you'll need to check though.

LannyL81

It is quite strange. Jumping a tooth on the timing set means retarding the timing.
When I have the balancer at #1 TDC...the rotor is well past #1 and half-way to #8.

I pulled the dizzy out....drive gear looks fine. Although unable to get it to go back in the way it came out.

Looks like I will be doing a tear down in the not too distance future.

...Roger...

Woh , back up don't tear anything down yet. I think you need to educate yourself on timing first,cam/crank verses ignition. Nothing said in this quote points to anything except retarded "ignition" timing(set by turning dist.).
Rotor halfway between 1 and 8 has the firing coming in late.

(Sorry if I have misinterpreted your post.)

cardo0

This is a great way to learn your engine or to blow your savings - its your choice. Unless you have to drive the car daily then get the books out and cover all the bases troubleshooting one thing at a time. Too many enthusiests here rip right into a low milage engine without ever knowing the real cause. And rebuilding an engine is not the place to learn how to troubleshoot what could be an ignition problem.

I just had my stethoscope (<$10 Hobo Fake) out today and thats where i would start with yours. Heck if i can listen to my solid lifters clatter (on the exh manifolds and on the block too) you should be able to hear and locate a engine knock.
Next the plugs - pull one at a time and lay the plug on the intake and watch for spark while the engine runs (or cranks).
I don't about your car but the '81 california vettes had an electric Qjet that ran closed loop by a computer. Yes, the first OBD I cars and should have error codes you can look up - but again i'm just guessing your car has this. Before i pulled the timing cover to look at the timing gear set i would spend the money at the Chevy dealer for a diagnose and again at another shop that i trusted to back up what they diagnose. $200 well spent that will save you much more than any rebuild.

That should be enough for now as i don't believe a compression test or leakdown will address the problem you have now.

Good luck and let us know more when you can,
cardo0

LannyL81

With regards to timing being advanced or retarded.....I say advanced as in the rotor was past #1.....which is actually timing retarded....but advanced to the next plug.....sorry I messed that up....been a long frustrating weekend.

As far as trying to listen to the engine....pretty much forget about it. It will not idle at all.....and driving it anywhere is doubtful as it is a manual trans and trying to keep it running and shifting is not easy.

Yes I have the CCC and the E4ME carb....which was all running really good until the timing jumped.

I need to ensure my balancer did not shift so I will set #1 TDC by watching the valves and see where the indicator aligns.

Nothing is going to get taken apart until I know more about what happened. That I have got to get my 95 oil pan gasket to seal.

dprinter1

I would be draining the oil into something I could easily inspect it in, i.e. metal in the oil. It won't cost you much, and will rule in or out, severe metal to metal contact. Just my .02 Sorry for your troubles man.

...Roger...

To check TDC you need to make sure #1 piston is at the top,the dist rotor will not be an indication.

I think disconnecting the distributor connector and making sure the initial timing is set correctly would be a good starting point.