engine knock bad!!

WOT said:
That sounds like exhaust noise. It seems too slow for it to be something hitting a piston (the exhaust stroke only happens every 2 revolutions, so exhaust sounds are usually slow like that). It is either leaking around your PVC breather where it goes into your exhaust or right at the manifold gasket.
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I agree...I'm telling ya, my buddies sounded just like that...He went nuts trying to figure it out. Dealer found it in 20 mins, leaky exhaust gaskets :p
 
If you think it's and exhaust leak you can turn a water hose on the head where the manifolds connect. While the engine is cold if the noise goes away or changes its an exhaust leak. You'd get close to that also buy pulling the plug.

When ever i developed a rod knock back in me younger days lad, i would find the culprit with the wire pull. Drop the pan and try to lap the journal back into shape. If that didn't work i would leave the wire off and drive until i got the money to have the crank machined or buy a junkyard block....
 
A LONG LONG time ago, mine broke the #7 intake spring. . . It sounded pretty identical to the vids you posted. I'd pull the valve covers again. :eek:
 
Roz-SRT said:
A LONG LONG time ago, mine broke the #7 intake spring. . . It sounded pretty identical to the vids you posted. I'd pull the valve covers again. :eek:
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If you are gonna' go through the hassle of pulling the valve covers again, at least use a mechanics stethoscope so that you can isolate exactly which one is causing you the trouble. However, I think you will be surprised at how noisy the normal valve train is. Even though they are hydraulic rollers, they still make a ton of racket. You might want to buy some of those oil squirt blockers that go over the end of the rocker where the push rod is so that oil doesn't go everywhere. If they are the fast bleed down type (I think Stink mentioned this), then they will be even noisier (which explains why these motors make so much racket).
 
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You said that you replaced the exhaust gaskets?...did you use OEM?...if not then that is most likely the problem....mine made the same noise when the shop installed the gaskets that came with the Bassani headers..
 
as the this moment, i've found out that the crankcase was under enormous pressure due to the pcv valve wasn't working and instead of sucking the vapors from the crankcase it was putting in boost air. (took oil cap off and vapor was shooting out).

I might be wrong but because the crankcase was under such pressure, it was hard for the starter to turn the motor, although i haven't tried turning the motor since we got it over to my shop.

We did a comp test on all cylinders and here are the numbers:
1-115 2-115
3-110 4-145
5-100 6-145
7-80 8-65
9-45 10-80

I'm waiting till monday to get a leak down tester so i can check to see where i'm actually leaking (valve, rings or head gasket)


I'm still wondering how my motor has took a turn for the worse. before i parked it was running smoothly.
 
exhaust gaskets are oem and i've double checked all bolts are tight even on manifold. all valves are moving like they should in correlation to each other.
 
71dusterjon said:
as the this moment, i've found out that the crankcase was under enormous pressure due to the pcv valve wasn't working and instead of sucking the vapors from the crankcase it was putting in boost air. (took oil cap off and vapor was shooting out).

I might be wrong but because the crankcase was under such pressure, it was hard for the starter to turn the motor, although i haven't tried turning the motor since we got it over to my shop.

We did a comp test on all cylinders and here are the numbers:
1-115 2-115
3-110 4-145
5-100 6-145
7-80 8-65
9-45 10-80

I'm waiting till monday to get a leak down tester so i can check to see where i'm actually leaking (valve, rings or head gasket)


I'm still wondering how my motor has took a turn for the worse. before i parked it was running smoothly.
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back 4 holes sort of low:(
 
How many seconds did you have the starter engaged for? And what the throttle valve open fully.

When i do this there is a black wire with a black connector right by the fuse box it goes to the solenoid. I hook my remote starter to it so you dont have to worry about firing the engine.

Also, was there this sound before? If not we need to not think about dropped valves or spun bearings, haha you can't do either by pulling the exhaust, intake or changing the spark plugs.

I know i sounds like i'm a broken record but you need to isolate the noise and to do that you need to pull the fire off each hole until the noise changes/stops. Then from there you can see if its the plug/wire swapped, or an exhaust leak.

Your last 4 are super low though as stated above.. number 9 is almost dead.
 
Have you tried a Stethescope to isolate the noise...or a piece of pipe---caution keep it away from moving parts...
 
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bigike said:
How many seconds did you have the starter engaged for? And what the throttle valve open fully.

When i do this there is a black wire with a black connector right by the fuse box it goes to the solenoid. I hook my remote starter to it so you dont have to worry about firing the engine.

Also, was there this sound before? If not we need to not think about dropped valves or spun bearings, haha you can't do either by pulling the exhaust, intake or changing the spark plugs.

I know i sounds like i'm a broken record but you need to isolate the noise and to do that you need to pull the fire off each hole until the noise changes/stops. Then from there you can see if its the plug/wire swapped, or an exhaust leak.

Your last 4 are super low though as stated above.. number 9 is almost dead.
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we started with cylinder ten and cranked 5 times. we did it with throttle closed and also open but found that throttle closed gave more psi.

The sound was not there before i parked it. this is why i'm so confused on how i all of a sudden got a knock. Been talking to tony and since my crankcase was under enormous pressure (dont know exactly how much but more than there ever should be) and he thinks that with enough pressure the rings could have gotten messed up.

I wish i could have kept the motor firing longer but with so much pressure building up we shut it off and tried to figure out what was causing the pressure build up.


On monday we are going to do a leak down test, which will pump 100psi into a cylinder and the amount of pressure lost is the percentage of leakage either through the valves, head gasket, or rings.

i know i still need to put valve covers back on and fire the motor and pull wires to determine which cylinder is causing the knock. On monday after leak down test i'll do this.
 
a note on the valves-when i pulled the covers off it seemed like only a few valves seemed fully open while the others were all relatively close to each other at full close. when we spun the motor they all looked like they were moving the same distance and not binding.
 
To accurately do a leak down test (and a compression test, as well), you need to put a couple of squirts of oil through the spark plug hole. This will help the rings make a good seal. When the motor is really running, there is a ton of oil splashing around on the bottom of the pistons and the cylinder walls. So, you really need to squirt some oil in there to help it seal. Plus, the rings are made to seal when the motor is warm (the end gaps close up when the motor warms up). So if you can't warm the engine up before you do the leak down test (as it is hell on the spark plug threads in the head), at least do the oil squirt.

Best of luck.
 
that's what my boss was saying that a squirt of oil will help with compression test.

Either tomorrow or monday i'll put valve covers on and try to fire the motor. while it's running to take the scope and try to locate the knock.

My boss believes there is no reason for rod/crank bearing to be bad because they would make a different sound and oil pressure would go down.

There is no slop in valve train. I wasn't able to move any pushrod down or up and the rockers are always in contact with the valve.
 
WOT said:
To accurately do a leak down test (and a compression test, as well), you need to put a couple of squirts of oil through the spark plug hole. This will help the rings make a good seal. When the motor is really running, there is a ton of oil splashing around on the bottom of the pistons and the cylinder walls. So, you really need to squirt some oil in there to help it seal. Plus, the rings are made to seal when the motor is warm (the end gaps close up when the motor warms up). So if you can't warm the engine up before you do the leak down test (as it is hell on the spark plug threads in the head), at least do the oil squirt. Best of luck.
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Oil should not be used in a compression or leak down test.

Oil can be used after an initial "DRY" test.

The oil will artificially seal the rings and negate the results of the test if done first.
 
i was just reading the thread about Bone pulling his motor. is there any way that a rod is bent because the crankcase was preassurized?
 
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