Mr Fufu

My '67 has an engine noise that sounds like its coming from the right front. The car has a stock 300hp/327, with factory air conditioning.

The noise is absent when the engine is cold. After it's fully warmed up, the noise is audible, but only at or near idle. It's a 'tap-tap-tap' noise, which also has a 'clunking' tone to it. Hard of course to describe in words. I got out my trusty engine stethoscope and tried to locate the noise. But it's not easy. I put the probe on each valve cover bolt. It seems louder, but not so much, at the front right, next to the A/C compressor. I probed that too, but could hear no distinctive tapping noise from it at all. That A/C compressor is in the way of the front right most valve cover bolt, so I couldn't put the probe there to check.

Once the engine is off idle, the noise disappears. The engine runs just fine, and strong.

On the weekend I was around some car buddies. One told me that the noise was probably from a lifter under the A/C compressor. He suggested I remove the valve cover and tighten each rocker stud nut by 1/8th of a turn. He also advised I use a thicker oil, such as 15W-40. I currently use 10W-30. The car has hydraulic lifters. I didn't argue with him but, I thought hydraulic lifters were not adjustable.

Before I start taking things apart, is there anything else I should look at? Is the advice I got worth trying? Should I try to tighten the rockers? And run a heavier weight oil?

Thanks for your suggestions and advice,

Frankie the Fink

Hydraulic lifters are ABSOLUTELY adjustable..
Run some Marvel Mystery Oil through the engine (follow directions) and then change the oil and see what happens...
It just sounds like you have a sticky/gummed up lifter.

L78racer

could be the fuel pump making noise.

still cruzin

Another thought? A lose or broken exhaust manifold gasket will give you the same ticking sound. Check that one first.

Bob

Frankie the Fink

vetsvette2002

Another possibility is a burnt exhaust valve.
A compression test will give the answer about the valves, I don't think a leak down test is needed if the first test reveals valve problems.

Don

jim lockwood

If the MMO doesn't "fix" the problem, this is what I would investigate next.

Tampa Jerry

I would invest in a vacuum gauge. The readings will give you insight into valve problems. Jerry

MikeM

Don't panic but it could be a rod knock or piston slap.

dplotkin

Engine noise causes much unnecessary anxiety. Odds are Frank is correct. Try it before considering worst cases, rod bearing, wrist pin and that...I have a 62 Bonneville 389 that developed a hot knock after I rebuilt it. Assumed the worst, gave the rebuilder a few sleepless nights, cut open the filter & found nothing and then decided to drive the **** out of it and let it blow if it's gonna. After 3 years and 20,000 miles I finally took a stethoscope to it and found the noise at the power steering pump. With a sigh of relief I left it that way!

Try Marvel.

Dan

domenic tallarita

Sounds like oil. slip a can of STP in the oil. could be a weak lifter. They have to bleed down then pump up with oil pressure. Also had the fuel pump spring break and it made a lifter noise.

Dom

hedgehead

Don't rule out timing chain slap.

Mr Fufu

Thank you everyone for your suggestions, from lifter, to fuel pump, or worse.

I'll start with the Marvel Oil and go from there.

Will keep you posted on what it turns out to be.

Cheers,
Alex

Vettegeezer

Alex, what oil pressure are you reading hot at idle?

hope2

Use a stethoscope and hunt. Sounds like fuel pump.

GearheadJoe

If you can manage the oil leaks, pull the valve cover and put your stethoscope on each rocker stud, one at a time. This will give you a very clear indication if there is a noisy lifter.

There are little clips you can get that will keep oil from squirting out of the rockers while you perform this test. With those installed, the main oil leak hazard is at the back of the head, since the engine is tilted down at the rear. You can mitigate that by jacking up the back of the car to level the engine.

I agree with the suggestion to use your stethoscope on the fuel pump too. I've heard stories of fuel pump noise being mistaken for a rod knock or a lifter noise.

Lastly, I also agree that a leaking exhaust manifold can create a noise that sounds like a lifter tap. Even if you have no exhaust manifold gaskets (the way GM built the cars), the manifold can warp and leak. Usually, if the manifold has warped, the leak will be at the center, where two exhaust ports are merged. A good first step would be to make sure the exhaust manifold bolts are tight.

One last thought relates to the fact that you have factory A/C. One of the brackets for the A/C compressor mounts to a stud that is installed to replace one of the exhaust manifold bolts (can't recall which one). The order-of-assembly is to install and tighten the stud, which clamps the exhaust manifold to the head. Then, the A/C compressor mount attaches to the top of the stud with a nut. I'm mentioning this because it is a PIA to tighten the stud-to-head clamping force without first pulling off the A/C compressor mount. Aside from that one stud, the other five exhaust manifold bolts are fairly easy to tighten.

Frankie the Fink

What the OP has NOT done is take a cell phone video of the noise, post it to Youtube and link to it here -- which would help diagnosis. I'm trying to imagine a "tap-tap" sound that also has a clunking aspect to it.

The sound in the beginning of the Pink Floyd song "Money" comes to mind...

Zoomin

RatDog

As suggested, try the Marvel Mystery Oil and report back if it works.

There was a thread awhile back extolling the virtues of MMO. My 327 had a ticking noise coming from the right front so I added some to the crankcase, drove a couple hundred miles, and changed the oil using 4 quarts of oil and 1 quart of MMO following the directions. The ticking disappeared.

The same thread read suggested adding MMO to the gas tank so I gave that a try, too. After doing this for 3 tanks of gas, my car has never run better. I am a skeptic turned believer.

Steve

Frankie the Fink

Sticky lifters were common "back in the day" especially among the Navy wives whose husbands were deployed from Norfolk for months and the cars got zero maintenance. We used to mix a cocktail of 50% kerosene and 50% oil and run it through the engine briefly to clean it out then change the oil - ticking gone. MMO is the modern equivalent and probably safer.