Reaching out the 300 collective brain-trust here to try to figure out a chirping/squeaking noise coming from my engine. This is a ‘78 block and head with a recent rebuild and has developed this issue.

Some information about the build is here: Yet another 300 build - Ford Truck Enthusiasts Forums

The chirp gets louder as the engine gets warm, but you can barely hear it sometimes even on startup. I’ve ruled out almost everything and am hoping to get some input. I’ve tried with the stethoscope to locate the noise but haven’t had much success locking into a specific point. It seems to be coming from the front top end of the engine.

Here is a link to a video I posted for people to give a listen:
Here is what I have ruled out: belts and accessories, anything transmission related (throw-out bearing, pilot bushing, etc.), bottom end bearings, distributor, oil pump, fuel pump.

It has Melling stock-type rocker arms with the grooved ball fulcrums. I pulled each, and there doesn’t seem to be anything visually wrong. I’ve readjusted preload multiple times, no change. Zero lash plus ½ turn. I had 3/8 ARP rocker arm studs installed so it’s not the simple torque down.

Camshaft (Isky 256) is straight (.0005 runout) and turns smoothly in the block, so I doubt its cam related. Cam lobes look fine and all lifters (also Isky) look good and are rotating just fine. The top end seems to be getting good oil, all seem to oil about the same except the #2 exhaust which is like one of those pop-up pulsating lawn sprinklers – it puts out a lot. I pulled that lifter, disassembled, cleaned, and inspected it. Everything seems okay, but it still does the same thing. I would change it out just to see if that’s an issue (I have a couple spare Isky lifters), but I really don’t want to do another cam break-in (and run that risk) unless that is my last option.

No bent pushrods, and none are plugged.

I’m running out of ideas. I did a search here and found where AbandonedBronco had a squeaking coming from his rockers, so I’m wondering if that might be what’s going on. However, I don’t want to drop the coin on roller rockers only to find it didn’t fix the problem, plus there’s the geometry hassle and the possible stock valve cover issue.

 

if you can determine if it squeaks every crankshaft revolution or every other revolution as in camshaft related, that would help narrow down the problem.
The flashing of the timing light might help.

 

Thanks for the response. After doing a bit more testing/listening and using your advice about the timing light, it definitely sounds cam/valve train related. The chirp has behaved a bit differently recently. Instead of a constant volume, it varies from a little louder for a couple seconds to quieter for a couple seconds. Also, if you rev the engine, right after letting off the throttle it is louder for a few chirps and then goes quieter. It also seems to be top end. When listening with the stethoscope, the noise seems like it is coming from around the front portion of the valve cover and not from down around the camshaft.

 

What valve springs did you use with the Isky 256 camshaft?

 

I'm running Comp Cams 903 Springs

 

The Comp 903 springs at .450" valve lift wouldn't normally cause rocker arm squeak but I don't know what else would.
You could try running the engine with the valve cover off to pinpoint if it is a rocker arm pivot ball.
Use something as walls to keep the oil from splashing out.
There have been cases with aftermarket rocker arms, where the hole in the rocker does not correspond to the hole in the end of the pushrod and prevents oiling to the top end.

 

As a follow-up on the noise issue, I had originally picked up a set of Harland Sharp roller rockers to install. Once I started working through the rocker geometry, though, it became clear that I’d need a few additional changes—longer rocker studs, either a valve cover spacer or taller cover, and custom-length pushrods (at least 10.5", and probably longer since I maxed out the available stud length during testing). I’m honestly not sure how AbandonedBronco managed to fit these under a stock valve cover.

Rather than going all-in on that setup right away, I decided to try a simpler (and cheaper) option first. I pieced together a set of NOS rockers and fulcrums from eBay and installed those instead, and the noise is now gone. I also confirmed that the “new” rockers are oiling properly, and everything looks good so far.

Previously, I was running Melling stock-style rockers with grooved fulcrum *****, so I’m not entirely sure what caused the issue. For now, I’ll stick with this setup and see how it holds up over time. If the noise comes back, I may end up revisiting the roller rocker setup—but I’m hoping that won’t be necessary.

Thanks for the help with diagnosing the problem.