Knock/rattle at lowish rpm. 455 *teardown/rebuild pg5*

An easy way to find out if it's ignition related with your DCR (detonation) is to buy yourself a few gallons of race fuel and run it with that and see if the noise goes away.

Hot spots in your combustion chamber could cause it too, but I would think it wouldn't be limited to low RPM partial throttle.

Perhaps try to richen up the fuel ratio (at least temporarily) to see if it makes any changes to the sound you're hearing.

 

disclaimer: The original set of plugs were installed with the ta212 cam about 50 miles ago, and have been through various carburetors and states of tuning. They do show the color change further down towards the base of the strap than that article wants. All of them have a consistent dry black film all over the plug, except the #7 which was new looking. I expected to see a sparkling clean #7 cylinder with the borescope, but its identical to the rest. Not sure whats going on there.

Unfortunately, the borescope I was able to get is not the kind where you can control the direction of the tip, so I could not look "up" into the chamber from the spark plug hole. The pistons do not show any damage or bright flakes, just a fairly even light carbon coating

 

There is VP 110 octane available just down the street. At this point I'd try anything. I can program the sniper to hit any AFR I want, I can try to bring it up a point or two richer tomorrow

 

I was able to make out "40" on several of the pistons, so .040 over I guess. Frustrating not knowing anything about this engine or how it was built

 

Idling and cruising after the heavy throttle obscures the chamber and plugs, making your light carbon coating fairly meaningless.
Without seeing anything, it seems like you have the idle and light throttle fuel adequate and are maybe too lean for heavy and full throttle. I'd ignore the number somewhat and see what the engine tells you.
If you are seeing signs of the plug being too hot at less than full throttle and hearing detonation while driving, it's wise to back the timing waaay down and add fuel... creep up on things from the safe side.

I'd be checking the oil filter for bearing material.
I think the black film could be from seafoam or possibly bad from the station.

 

Still doing it, might be getting a little better. I'm tempted to drive it around for a while and see if the seafoam helps. I turned the target AFR down from 14.0 at cruise to 13.0, and the wot from 12.5 to 12.0, no difference really noted

 

Filter pics are on page 1, some shavings but no real shiney bearing looking stuff. After I installed the cam, did a 20 minute break in and drain, that oil/filter was installed

 

I wouldn't add seafoam and keep doing it.
I don't have any hard proof to offer on the seafoam but I think it it would both affect AF ratio and lower knock resistance (or they would sell it as some kind of octane booster).
I haven't read every detail of the thread, but the timing tape seemed to pop back into my head.
Was TDC verified with a piston stop and ascertained later to prove the dampener isn't moving?
Again...severe enough detonation to hear in the car isn't going to cure from going slightly richer.
Why are you trusting your AF readings when you have clear signs of mechanical trouble?
What if your O2 sensor is off a tiny bit or any number of potential reasons for error?
Back the timing waaaaayyy off and creep up on things from conservative settings.
You are destroying your engine just a bit more every time you run it with detonation.
(I can't hear the video too well, it could be a misfire from too much plug gap or weak spark)

 

All I heard was one prominent "double click" at 3 seconds when you started to rev up at the lower 1500 RPM. Then I heard the same "double click" as it came down at 6 seconds, maybe 2000. That doesn't sound like detonation or anything internal to the engine if that is what you are hearing.

 

The tick is from 5-6 seconds as I apply the gas

 

I did use a piston stop and degree wheel when I installed the cam. I have not verified them since, but TDC on the balancer does line up with the piston visually being at the top of the cylinder.

 

I did just find an exhaust leak I'm working on this morning. Stock manifolds with TA downpipes, one of the bolts on the downpipe connection is tight, but only because it is siezed/cross threaded. The bolt rotates and there is black all around it

 

Car is a bit quieter overall, but my original tick is still there

 

It will do it in gear while stopped and revving against the torque converter with the brakes on, right about 1700-1800 rpm.

 

I backed the timing way off until it barely idles, around 4*, it still does it, maybe a tiny bit quieter, but probably because its not making much power.

 

3 gallons of 110 octane added to my 1/2 tank of 93 made no change. I'm guessing its not detonation at this point, bewteen the race gas and dialing the timing back. I've checked the flexplate and torque converter repeatedly, as well as the front accessories and the valvetrain. I'm going to swap a carb back on in place of the EFI, and after than it looks like its going to be time to chase down an engine hoist and stand.

 

Is it possibly the injectors?

What does it feel like through the gas peddle when that noise happens?

 

I won't say no, but it would be the loudest injectors ive ever heard. Gas pedal feels normal.

The strange thing is that the car was running and sounding awesome, ran a quick errand and on the way home the noise started. I was just cruising around, not being agressive at all

 

Swapped the carburetor back on, no change. I picked up an actual mechanics stethoscope, and on the intake and head near the #7 cylinder there is more noise than anywhere else. Looks like the big buick is coming out, unless anyone has other ideas?

 

I'll search, but anyone have any luck removing the oil pan with the engine installed? off the mounts and jacked up, obviously