Not a good sound from engine

[jagarra]

I have been working on my truck the last month or so. Fixed so many items I am loosing count. this truck had sat for the last 6 years or more. Engine would not turn all the way through, freed it up with MMO. Put the top end back together, replaced the gas tank, cleaned the fuel lines. Plus a bunch of other things I found needing attention.
Today was the day I figured I could fire the beast. Put the tank in, connected the fuel lines, added gas to the tank and cranked it over. No luck, no gas getting to carburetor. I had cleaned the fuel pump, but there was no gas in the fuel line anywhere. It would try to start when I poured gas down the carb. so I went to Napa and got another fuel pump.
Cranked it some more and finally gas got to the carburetor and she fired and purred. Then this knocking started, went away and then came back again. The engine was running at a fast idle, blue smoke was coming out of the exhaust, but that may be from all the MMO I poured into the cylinders.
According to the odometer there is about 67K on the clock. from what I saw inside the engine portions I took off, that may be correct, very little gunk or sludge build up, pretty clean.
Any ideas out there????

[AZKen]

Lets hope it is spark knock/detonation/pre ignition/timing. YOU have to tell us where the noise is coming from with a broom stick to your ear and touch all around the motor. Could be piston slap/rod knock, exhaust leak, valves, all kinds of bad or maybe not so bad. Gotta isolate the noise to upper or lower or whatever. Need more info. Smoke is probably MMO, blue is oil. Could have 367,000 miles, right? The fact it would not turn over is NOT a good sign, whatever you busted loose could be a problem....rings....rust..... Hope you are monitoring oil flow. If you only "cleaned" fuel lines and pump, you may have introduced "varnish" into engine which is bad. ALL lines, pumps, filters should be new after 6+ years of sitting. You can't clean fuel lines because you can't see inside them. Buildup on walls will come loose after awhile. Carb should be cleaned and rebuilt. Run it off a clean gas can direct to fuel pump if not sure. What can a person clean fuel lines with and be sure they are clean?

[jagarra]

I plan on using one of those stethoscopes to try to isolate the noise. I cleaned the lines using carb and throttle body cleaner. I would cap the end fill it and let it sit over a couple days then drain. I did this over a period of a couple weeks. As far as I could follow, the vanish extended to the filter and pretty much stopped. Filter housing was removed and cleaned up, carb rebuilt.
I too am thinking that the noise may be associated with the interference issue. I will see if the smoke clears up, if not ,then I may have a ring problem.

When I put the distributor back in I set the timing statically about 10 degrees BTDC. Didn't set the dwell. The noise doesn't sound like pinging, too deep, no load.

[AZKen]

Pre detonation can be a hard knock sound. You can move dizzy while running to see any change. Not to say that varnish is you problem. It probably is not, but cleaning fuel lines is not the way to go after 6+ years. You could have loosened the gunk just enough to flow when under suction from pump. Who knows? But it really is not worth the risk. I am not at all a expert on the V6 (if that's what you have) but the Jolly page says 5 deg BTDC and you need to set valve lash to that page also. It's hard to say what the noise is. If it's truly a knock maybe not piston rings, be sure it's not exhaust leak. That can sound exactly like a rod knock also. Your plan with stethoscope is the answer. I'm hoping for the best. Later.

[FetchMeAPepsi]

Originally Posted by AZKen

Pre detonation can be a hard knock sound. You can move dizzy while running to see any change.

I did not know this! I just set the advance on Cecilia, changed the oil, and started knocking. I wonder if this is the problem? Added to my list of first things to do! Thanks AZKen!

Carry on, I was never here!

[jagarra]

I checked the oil level before I fired it this morning. Even thought I put 5 qts in there when I changed it, it was barely touching the dipstick when I checked it. Topped it up, put the battery back in there and started it. Well it made a little noise today, different than yesterday, so I went around the engine with the stethoscope listening to the engine. Most of the noise now seemed to be coming from the valve train, there was a louder knocking sound around #3, when I placed the probe further down the block.

I let the motor warm up and gradually the bad noises seem to disappear, just the rattling of the rockers. checked the dwell, it was around 31 degrees, timing was around 20 degrees, but I was turning 1000 RPM. Disconnected the vacuum advance line and it was sitting around 8 degrees, pretty good for this altitude. In the past I have always added 1 degree per thousand feet above sea level.

So I let it run and run, smoke mostly disappeared, still see some traces, but I figure the valve seals may have dried out a bit and let it ride for now.


Adjusted the carb, added the air cleaner and everything in the motor seems good for now. YAHOO!!!

[AZKen]

I should have said "detonation" (not pre detonation) and "pre ignition"....spark knock to some. Sometimes it's hard to figure out what is causing the high heat in chamber. It can just be timing or valves not right, not sure.

Sounds like you got lucky, hope so. Be careful with motor for awhile til you can get some heat and oil pressure readings. That's VERY important. Your oil filter probably filled up and reduced stick reading.

This is a good time for all who can, to donate to 6066. It's easy and rewarding. Maybe you have saved hundreds $$$ in repair costs by info given sometime in the past.

[jagarra]

I thought I would share some pictures as I was doing the final tuning of the motor. The bad knocking sounds are gone now, starts good too. Seat of the pants says it still runs up a bit rough, not sure if that is due to deposits burning off or what. Doing brakes now.

[AZKen]

Nice looking motor. Good job with the restart. Gotta expect some carb, spark and valve tweaking after you read up on the specs in the Jolly section and other posts and after she "grooves" in again, (gets rid of MMO and old carbon). Plugs may need cleaned after awhile. Run it with valve covers off for a minute and see if oil is gushing up in there. You got yourself a big block GMC!

PLEASE NOTE EVERYONE: I put a note about donate in a post in this thread, I did not mean that to be directed at the poster. After I realized it could be taken that way, I posted that message in the general forum. I could not edit my post above. My apologies for being thoughtless.

[FetchMeAPepsi]

Congrats on geting off the "knocking horse" HAW HAW HAW! I hope mine is just as easy to fix. Forgive the dumb humor, I'm really tired and it's been a long 12 hours of work.


I promise it was funny in my head!