56 engine knock with hot engine only

[Hillbillycat]

Well, it's been a while now since my last post, but I wanted to let you know that I got everything back assembled with a set of new lifters and pushrods. Was able to take her for a test drive today just in time before snow will hit us tomorrow.

While I was in there and had parts off I took the time to detail stuff, like new paint on the oil canister, power steering pump and brackets and such. Also painted the block where accessible with a brush. Looks so much nicer now.

Was able to eliminate the ever since annoying leak on the power steering canister while it was off.  The gasket was cracked so it seeped out under the can.


The knock seems to be gone so far but doubt that I got the engine hot enough with today's ambient temp of 0°C. So this needs to be investigated in spring 2022.

Thanks to all of you who guided me through this. You´re the most.

[Lexi]

That is fantastic news. Hope the good news continues in the Spring. Clay/Lexi

[James Landi]

this is great news especially for you--- I encourage you to tell us what you found regarding the push rods-- bent one(s)--- some not rotating--- lifters, rockers?   james

[64\/54Cadillacking]

Looks awesome! Lifter taps and ticks are really annoying and knocking is even worse. Thicker oil and some Zinc additive usually does the trick. Running it hard every once and awhile helps clear out carbon deposits and frees things up inside the engine.

[Hillbillycat]

I found nothing more except the things I had posted previously.
I hope not to need thicker oil for I love how easy the motor cranks with the 15W40, even at low winter temps.

[Hillbillycat]

Well, wanted to update you on my engine noise.
It´s still present. New lifters and pushrods plus cleaning didn´t do much difference. Maybe a tad less.

However I discovered that my vacuum advance is bad again. Does not hold vacuum.
Can a bad vacuum advance cause this knock?

[Roger Zimmermann]

I don't think so. At idle, there is almost no vacuum because the source for the advance is ported vacuum and not manifold vacuum.
I would try this at your place: remove the mechanical fuel pump, and take away the actuating rod. Install again the mechanical pump and try if the noise is still present.

[James Landi]

I hesitate to say, usually not--- but perhaps... when you press down on the gas and the engine begins to knock, the old broken vacuum advance will  likely be in the entirely off line position... now if, when you replace the advance,  the stator plate is stuck in some advanced position, that could be your problem.  WHile replacing the advance, make certain that the stator moves easily with slight hand pressure... doesn[t move too far as the range of movement is controlled by the vacuum advance---also check for "lateral movement" as I have encounter old V 8's that had a worn out bushing on the center of the stator, so that the plate could be moved sideways---there should be no looseness there, and if there is, your dwell will constantly change as the stator can be pushed sideways.  Then after you replace the vacuum advance, try "moving" the stator with the new advance by sucking on the vacuum side.  If memory serves, the advance on the '56 has a steel 1/8 pipe, so you'll need to purchase an 1/8 barbed fitting and some  hose to fit the barb... you should be able to produce enough vacuum with your mouth to move the stator plate... not very far really, because the vaccum can is engineered to take some very high vacuum.  Also, this is a good time to check the  spring weights on the distributor... they also affect timing, and if those weights are stuck (usually occurs from rust) or the springs are struck, your timing could be off as well. Hope this helps, James

[Hillbillycat]

@Roger:
you mean disable the mechanical pump and run on the electric aux pump only? To rule out pump actuator rod noise?
I had re-lubed the fulcrum last summer - no avail.

@James:
Engine begins to knock when on idle. On WOT there´s no knock present.
Centrifugal advance is working, lubed and free of rust.

I´ll have to replace the vacuum advace anyway and will check the stator movement.

[Roger Zimmermann]

@Roger:
you mean disable the mechanical pump and run on the electric aux pump only? To rule out pump actuator rod noise?
I had re-lubed the fulcrum last summer - no avail.

This is exactly what I'm suggesting. As explained last year, I have this noise too. I however have to confess that the noise on my car is NOT near the #3 cylinder.