SBC mystery knock

Did you come up with a cause to the noise? I have the same problem with a 73 350 SBC.
I have checked everything suggested in the past without resolution. If I am using the tube it sounds like the noise is coming from the timing chain cover.

I would guess the only way to check the fuel pump is remove it and inspect it?

 

My noise was a bent rod on #2. It sounded like a cracked skirt. It would always knock while under load. It knocked going uphill on my driveway. I also tried everything listed so far. I finally pulled the motor,took it all apart, and found the bent rod. Its an 85 gm crate motor. I think the muffler shop filled the cylinder with gas? I had to go and get it cranked while they were putting exhaust on it. The hot wire was off the hei. The engine also vibrated until I replaced the rod. Now it doesn't.

 

Before you go taking things apart check the exhaust maifolds/headers. make sure they are tight against the block or gasket. I have seen a few "engine" tick or knocks that were simply loose bolts on the exhaust. My brother chased a tick for days on a SBC, I mentioned the exhaust to him, he tightened the bolts and no more tick, It sounded very much like a lifter.
Maybe not your problem, but it's the first thing I check when I hear a tick.

 

I have seen rod bearings only knock after they warm up, alot, start pulling plug wires as suggested, before you go crazy looking for something else. Have you checked your muffler bearings? sorry had to.

 

Or if it gets worse because the piston is hitting the head since there is little / no cylinder pressure

 

53, there is a chance your timing chain is stretched and slapping the timing case cover. has happened to alot of sbc's. I had one that was so loose, it rubbed a hole through the cover.

 

I had the flex plate crack on a SBC once. Baffled me for a while, thought it was a rod or something. I would check that.

 

Flex plate crack, loose torque converters can do it too. I use a wooden dowel to ferret out noises in general. Did you loosen all alternator, fan belts to rule out the belt-driven possibilities?

Wrist pin knocks are a double knock, it takes a trained ear to hear them though. I've also seen spun main bearings with great oil pressure, those are a heavier knock.

If you want to adjust your valves quickly, with it running, back them off one at a time until it clacks, tighten it until that noise goes away. This is your zero point. Give it a 1/4 turn, wait for the lifter to settle down, give it another 1/4 turn, wait again and go to the next and so on.

Bob

 

I bought a coronet once that had a slight knock, wasn't constant. Turned out it was a loose torque converter. Sound travels through steel and sometimes makes it difficult to pinpoint origin. Probly not your situation but thought I toss it in.

 

With engine running, back off on rocker nut until it starts clicking. Slowly, in small increments, tighten the nut until clicking just stops. this is zero lash. Note position of ratchet handle and turn in slowly (in increments) one turn. the extra 1 turn puts the piston in the lifter somewhere near the middle of it's travel. (which is the object) Some will say 1/2 turn, quarter turn, two turns, etc.. But the truth is, the only way to know for sure how far to go is to know the specs on the lifters you are running. Then you have to figure the true correct setting based on thread pitch on the rocker stud. Go 1 turn and you are good. Btw, the cutout valve cover idea is a good one. Learned that back in auto repair class back in the 70's.

 

well, after doing alot of research it still has me baffled...

it makes the noise loudest at about 1500-2500 then seems to tapper off a bit (could be the straight exhaust drowning out the noise). but like i said, in acceleration when the RPM's quickly rise the sounds almost sounds high pitched and becomes rapid with the RPM and when the sound becomes frequent enough it virtually sounds like a whine..

 

i have a friend coming over tomorrow to help locate the noise.. he's kind of a uber mechanic, real smart common sense guy. hopefully the help of a more experienced hand will help me deduce it down to one or two issues. luckily most fix's are relatively inexpensive it seems.

 

Possible u joint .Lazy lifter and other things mentioned as above ,Good luck chasing this down ,

 

does the engine have flat tappets?if it does you gotta add an additive to the oil because new oil doesn't have any zinc in it and you lifters could seize and wipe the cam out,seen it a few times.The government decided to remove the zinc from oil in 2003 because of emissions reasons engines these days have roller lifters in them so the need for zinc isn't as important...

 

well, i have deduced the knock to passenger side engine.. used a fiberglass CB antenna to help resonate and find the source but i think it was a bit to long to get a clear enough to pin-point, kind of sounded like it was coming from everywhere on that side

 

LOL, it's amazing at the amount of hair a person can pull out because of engine nosies. An engine is a rotating assembly. Just start at one point and work yourself through it until you find the culprit. Sorry not laughing at your problem, just seen it so many times. Just stay cool and take your time.

 

Some of the crate motors from GM did not have long skirts on the piston and the piston would slap a little making noise.

 

hmm well even though when i got the car the appraisal said it was a goodwrench crate engine, it may have the short skirt pistons, idk why it would just start doing that.. plus i've heard piston slap sounds more chatery where as my sound is a more distinct knock

 

Maybe it's wanting you to open the door? Just start yelling back at it "I can't hear you"...
Drill instructors always thought it worked for them...

 

These additives arent miracle workers, you need to use them when breaking in the cam. If this wasnt done, adding them after the fact wont make things better. If the cam was broken in using just the newer type oil, chances are the damage has already been done.

 

I've always understood piston slap to be cold, not after warm-up, when things have expanded, and clearance taken up..
Also, my little Ford slaps... and it is quite more of a knock than a chatter. It goes away when warm, and is NOT RPM sensitive...it exists only at idle.
I don't see a flexplate expanding enough that it would start AFTER warm-up, either, if cracked?
But...???
How is oil pressure? ( I know...it goes without saying, but still...)
Does it get louder on the throttle?

 

I had a sbc in a van that always made a noise, didn't care because it was hard to get to the engine and take the oil pan off. But once I was going further out of town on a trip so I thought I'd better check the bearings. Pulled the pan they were all great, it was the crankshaft end play. I could move it back and forth probally 3/8's of a inch. Engine must of had a stiff pressure plate behind it in it's life time.

 

have you drained the oil and put a magnet in it to see what you can get out of it?

see if the engine is leaving behind traces of metal, either drain the pan and save the oil and check it out, or pull the pan and have a look see..

maybe take a you tube video of the sound and put it up for us to hear it?

 

i readjusted the rocker arms and thought while i was at it i would adjust the carb too.. car has not ran that smooth and nice in a long time.. had the damn thing sitting in the parking lot here at the apartment (i know my neighbors must love me with the straight exhaust echoing under the car port) and let it run for damn near 30-40 minutes, way more time than it normally starts to knock at, put it in drive and butted it up to the curb then power breaked it a bit to see if i could get it to start knocking since it only does it warm and in drive.. fucker would not start to knock!!!! i was feeling pretty good... then i was like "shit, lets go around the block ol girl!" i made it about 3 blocks before i noticed the knock.. so i drove around for about 7-10 minutes to get it to knock a tad louder then brought it back to park it... after extensive searching and using a long fiberglass rod (thought that would resonate sound pretty good and alow me to stand outside the car with it in drive stuck on the curb) and found the sound to be rather neutral to what side it sounds like its coming from... held it all over the motor and could not hear the knock.. but did note its loudest UNDER the car and towards the rear.. begining to think the flywheel is the culpret.. but time will tell with more checking.. trying to be pacient and take my time before jumping to conclusions..

i will see if i can get clear enough video of it with clear sound.. i will post it if i can get a good one.

 

good luck buddy, on a side note i got thos offy intakes blasted for you, they look great!

 

thanks matt!!!! if you guys wanna come over later feel free!! this knock is drivin me to drink.... heavily... lol

 

Sorry if this has been mentioned, but I don't want to read 55 replies to find out; my knock was from the rockers contacting the after market valve cover. Might want to check the inside of the cover for marks if that hasn't been done..

 

yes a flywheel will make noise before and after warmed up. been there !!!!

 

What he is saying, is that it is NOT making noise until a LONG ( evidently ) way AFTER warm up.
I would think that a flywheel/flexplate would be less responsive to hot/cold, and pretty much always knock, no? especially if cracked?
I don't know...I've run Ford's for an eternity, and have never had a cracked flexplate/flywheel...

 

I doubt it's the flywheel if it's getting louder or atleast noticeable after it's warmed up. Something internal..