So L48 - 4 Speed. Started making a loud ticking sound today, increases and decreases with RPM. Noise seems to be more prevalent on the passenger side. Also the idle seems really rough all of a sudden.

Whats new - Water pump and thermostat a few weeks ago, no overheating or leakage evident now

New tank of 93 octane gas - tank was pretty empty, tried to convince myself it was not 93 octane fuel. New gas station possible they mixed up the pumps.

What I have done so far.
1. Rechecked the timing, all in at 34 degrees with vacuum disconnected.
2. Listened with stethoscope and was unable to isolate on top of engine or valve covers.
3. Did the disconnect at distributor of each plug wire, none made any difference in noise. Read that was a good test for rod knock.

At this point I'm thinking exhaust leak, at the shorty header flange maybe. Will tighten all the header bolts tomorrow AM.

Anything else anyone can think of for me to look at? Fuel pump rod maybe?

 

Could be exhaust leak as you already mentioned and place the stethoscope on the fuel pump to check the rod.

 

Fuel pump...?
seems to be the season

 

Spun a lobe on the cam?? Possible. High zinc oil??

 

Put a vacuum gauge on the engine and see how it reads. The gauge will determine if the engine has a dead cam lobe or burnt valve. See You Tube on how to read it. Jerry

 

Could be as easy an arcing plug wire too.

 

Scott, is it an engine noise or a suspension noise - i.e. is the noise keyed to engine rpm when stationary, or speed of the vehicle moving down the road?

Good luck... GUSTO

 

dust cover over flywheel. got me twice, once on my c3 the other on a 69 chevelle I had

 

Ticking. Idle becomes rough.

We all pretty much have an idea what this is.

So, tell us about the history of the oil being used.

 

Pull a valve cover and start it see what ya got. Ck your springs..were you romping on it before this happened?

 

Not a coincidence that the noise and misfire occurred at the same time. My first reaction would be ignition system. If you don't have any test equipment, run the car at night in the dark with the hood open. Look for spark arcing. It's a lot easier to see in the dark.

 

I've had a bad harmonic balancer rub the timing chain cover and sound like a rod knock.

 

Update- still ticking. Found the header bolts to all be pretty loose so tightened them up. Found the HEI distributor brand in the PO paperwork and it calls for .045 spark plug gap so I regapped all plugs from .035.

Found one header bolt on passenger side the middle 2 exhaust mounts, one stripped, one obviously drilled out and replaced with a larger bolt.

Took the passenger valve cover off and all was tight. Even started it and ran it with valve cover off. No ticking noise coming from there and noise was not louder.

Could not get to the fuel pump but did find the rigged up fuel line was leaking. Also seem to have an oil leak coming from up by the fuel pump.

Next weekend I’ll pull the fuel pump and maybe rig up an old electric pump to bypass it and verify it clears the noise.

Finding lots of leaks pretty evident the PO did not drive much as seals everywhere seem to be springing leaks. I think I’ll try to plug as many as I can and keep on the road this summer. Probably pull the motor and trans this winter to get everything sealed up tight again, fix the stripped header bolt while it’s out.

Took it for a shakedown drive and plenty of go. Idle is smoother also not sure what helped that the tightened exhaust or regapped plugs.

 

All I know is the PO had it rebuilt with a roller cam and 10-1 flat top pistons in 2015. I believe he was running 5W-30 synthetic as he gave me one partial full bottle. I changed it to 10W-30 synthetic a couple weeks ago and put in new plugs. Oil pressure seems high to me, drops only to 60lbs at idle when warm, maxes the gauge at 80lbs at 2500rpm. I personally don’t trust the electric oil gauge but have not verified it. Plenty of oil flowing to the top end when I had a Valve cover off today.

 

Its definitely engine as it matches the RPMs. Definitely isolated it to the front passenger side. At this point I think the fuel pump is the likely culprit.

 

Also, a lifter may've puked its clip & guts. Pull valve covers and check for any rocker that's too loose

 

hi OPs indicate rebuilt w/ hi-volume pump (often more trouble than benefit in anything other than race car)

 

SVASSH, you are a lucky man.
90% of the time that ticking is a camshaft retiring and doesn't want to play anymore.

 

Is it making the noise at the same speed as the crank or the cam (1/2 the speed)
You can mark a pulley and listen that may help narrow it down
Longshot but have you pulled a belt off and started it?

Had a noise similar drove me crazy it was the holley fuel pump, 2 of them back to back.

 

you probably just need to lash a rocker....have your tried using a long screw driver and sticking the handle in your ear, then placing the tip on the object you want to listen to. IF its louder at the front of the valve cover than the back it may be a lifter or rocker. You can put the tip right on each header to see if you can determine if its a cylinder... If you can reach the fuel pump try and get the screwdriver to the top of it...


FYI I've had a gas station put regular gas in the high octane pumps and I could hear the detonation, but it'll be in all cylinders...I dont go to that station anymore no matter what