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Engine Knock!! Any small block experts in NE Ohio
Hello All
well the dreaded day finally happened...an engine knock. Its a 351W 69 block, 60 over. It was built about 7 years ago with only 3800 miles on it...till now no problems with it. I have a 6000 rpm chip in the MSD and I don't think I have ever used its technology No loss of oil pressure. It starts up fine and is quite as it warms up and the oil pressure starts to drop down...at around 1700 rpm and above it knocks. I have been looking for the easy problems...rocker arm push rod lifter....but to me those would be a tap and not a knock. They all seem fine I changed the oil...nothing in the oil as I drained it over a screen...no gold glitter in the oil etc. no smoke, no oil in the water or water in the oil any suggestions....? I am not sure what the next step is...Pull the intake and look at lifters...It has been suggested to me a cam bearing....not sure what I can see from the top. The noise seems to be at the head gasket level of the block not down low. You can "feel" the knock in the engine If anybody lives in NE ohio (Willoughby Hills) and knows anything about small blocks...drop me an e-mail you are more than welcome to stop by and listen thanks for any any and all help John |
Sorry, I should have read closer.
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I don't live anywhere near there,however, I might give you a tip to help isolate it. First, I wouldn't discount it being valve train related...they can put out quite a knock under certain conditions. If you isolate the cylinders on at a time, pull a plug wire, if it's a bearing knock it will quiet down. Loss of pressure could be through a lifter issue, so that isn't neccesarily a bearing. Years ago, we used to check the oil pressure bleed down ofter the engine was shut off. That gives an indication of the bearing condition. If there is another problem creating a loss of oil pressure, that wouldn't neccesarily be an accurate test.
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Can you tell if it's at crank or cam speed? Remember, the crank is twice the speed of the cam.
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I had a similar problem on a crate motor I purchased. Knock upon acceleration with and without load, no noticible change in the oil pressure... Turned out to be a spun rod bearing and the piston was slapping the cylinder head.
Good luck and I hope it turns out to be a minor issue... |
I second the spun rod bearing.
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I have pulled the plug wires one cylinder at a time.....to me no noticable difference in the sound.
I don't have any expierence with damaged engines and the various sounds they give off. We had a stethascope out....lots of interesting noises in a running motor I am going to go through the complete valve train...I have a hydraulic cam...so I will redo the 0 lash, look for a bent push rod check all the rockers etc. If that doesn't work the intake will come off to check lifters....and then pull the oil pan and see what I can see. I don't want the motor to go catastrophic as I would like to save the heads, valves intake etc.etc John |
I usually just take a heater hose and hold it on the oil pan. You'll know immediately. Many times, you can't tell at the top end of the engine.
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I have seen this more than once. I would hazard a guess that you are running a flat tappet cam??
If so you probably have 1 or 2 lobes and lifters worn down. They sound like a knock.. If your oil pressure is still decent that would indicate that the bearings and important oil bathed stuff is OK! Pull the lifters and check those first. The contact face should be convex on all lifters.If you put 2 lifters end to end..flat face to flat face they should "rock" on the high spot in the middle of the face. John |
yes I do believe its a flat tappett...as its not a roller cam....are there any other choices?
I have roller tipped rockers from Scorpion...Comp cam and lifters, push rods and the heads are from Powerheads cast iron CNC ported here are my cam specs Intake .523 Exhaust .517 running a Stealth intake with a Holley Avenger carb If this turns out to be the problem...what causes this to happen? John |
Hello Siverback51
sorry I missed your post....I am not sure if its at crank or cam speed. Part of the problem is..... these cars are so darn nosy......I like that 99.9% of time, except when trying to hear a noise and where its coming from!! John |
Regardless of the noise, have you cut the filter open to check for brg metal etc, bearing metal will end up in the filter, cam or follower metal will end up on the magnetic sump plug.
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I have saved the filter and I am cutting open later today tomorrow. I don't have a magnetic drain plug !!! but will next. The oil looked clean....no glitter in it all.
I am going to strain the oil through a cloth towel to see if anything is left behind that way that was too small for the screen I used and went threw John |
John, do you have a small magnet that you drag thru the old oil if you still have it to check, as long as the container was clean it might help your check.
If you remove all the rockers and check at each pushrod for equal camlift with a mag based dial gauge the dud cam lobe's if any should be obvious.( If your cam is a dual pattern the ex lobes may differ from intakes, but exh/exh & int/int should all be the same within about 0.005". If you have enough to make a noise it will be much more. |
Engine noises are quite possibly the most difficult of all things to diagnose. I would not rule out a loose crankshaft main bearing in this case. The clue being the knock comes on as the engine begins to warm up.
Do let us know what you find. |
Hello All,
probably the bad news I knew was coming....I cut open the oil filter today out in the sun.... When I took out the cartridge the bottom of the housing was full of golden copper colored particles and pieces.....as was the outside of the filter element. The oil in the filter looked like I was mixing in gold metal flake into the paint When I drained the oil and looked ai it was very cloudy and overcast and didn't see any glitter in the oil....a sunny day sure helped I guess that means a main bearing almost for sure. How do you diagnose what caused the failure in the first place? I am trying to look on the bright side...more power and its almost winter...now I have a winter project. any suggestion and recomendations would be appreciated John |
Hello All
A quick up date on the engine knock. I pulled the pan and found the #3 connecting rod bearing was spun. I think I caught it early as the bearing had not turned blue from the heat. The tabs were gone that hold the bearing in place The crank...to me...does not look all that beat up..but we will see how it all check out. I was never happy from day one with my oil pressure.... now hopefully we will see why. I have a feeling that I had a "loose engine" tolerances...maybe even side clearance issues The engine is out and I took it over to a very highly recommended engine builder, who's day job is for a NASCAR/Bush race engine builder here in the Cleveland area He is tearing it down this week, so we will see how it checks out I will keep you informed John |
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