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Old 07-23-2014, 05:35 PM   #1
Douglas Brown
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Default 78 C3 Oil pump knock??

Breaking in a 350 CID 300hp, re-build.....I have 3 - 4 knocks then pause and repeat 3-4 knocks the pause, sound coming from oil pump area of motor. used one of those stethoscope to listen, sound coming from oil pump area loudest near oil filter and oil pan around oil pump.
the rest of the motor sounds like it should. oil pressure @ 2K 50lbs 35K 70-75lbs gauge reads pressure holds, when back 950 knock, knock, knock some times loud sometimes not.
I used the pump from the 350 I replaced....
Has any one ever had a oil pump knock?? if so what did you do?
I think it needs to be replaced?

Last edited by Douglas Brown; 07-23-2014 at 05:38 PM.
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Old 07-24-2014, 12:31 PM   #2
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cannt be from distributor since it connects to pump?
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Old 07-24-2014, 01:56 PM   #3
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If it's an automatic, check the flywheel for cracks, loose converter bolts or loose flywheel bolts.
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Old 07-24-2014, 02:10 PM   #4
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So many things can cause that kind of noise. None of them are good. I agree with bashcraft for starters. If that checks out, I would have to think that you have a bad rod or main bearing. Automatic or manual? The thrust bearing clearance could cause the crank to "walk" in the saddles but that would be worse with a manual.. Is there any movement at the front, such as the balancer? Can you see it moving in and out ever so slightly at idle?

I was given a forged crank when I was building my engine that came from a truck. I was really good looking until I started looking at the thrust bearing surface. There was significant wear from pushing the clutch in over the years wearing the crank badly. So I didn't use it.
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Old 07-24-2014, 05:37 PM   #5
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It's a manual trans. I go out and run it. listen, come back in and think it through..
I have to rule out pump, dose not make since. it sounds rhythmic, possible end caps??? the knocking dose not stop when using clutch.....
Trying to contact builder, and have a mechanic coming over to test AC vac, to see if it holds pressure. it's a new system never has been charged, so I want to know if it will hold, but now..I have him wait on the charging and look at the knock.......I am hoping minor problem, but expecting major...pull motor take it back to builder..I do not know .????
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Old 07-24-2014, 05:38 PM   #6
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Quote:
Originally Posted by MelWff View Post
cannt be from distributor since it connects to pump?
Agreed
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Old 07-24-2014, 05:41 PM   #7
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Default Guess I wasnt clear

Quote:
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Agreed
What i was asking was are you sure the noise isnt from the distributor?
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Old 07-24-2014, 05:42 PM   #8
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Quote:
Originally Posted by bashcraft View Post
If it's an automatic, check the flywheel for cracks, loose converter bolts or loose flywheel bolts.
It is a manual trans, thought about the bolts but it would stop when pressure is applied to the pressure plate, and the knock would be a single tick as it traveled around the bell..not... knock, knock, knock and a pause then repeat the knocking.....
Thanks for the input.
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Old 07-24-2014, 05:47 PM   #9
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Quote:
Originally Posted by MelWff View Post
What i was asking was are you sure the noise isnt from the distributor?
I thought that too, but the noise is located loudest at the back of the pan to forward of the filter. using a stethoscope to pin point the noise.
The further away from that area I go the lower the noise
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Old 07-24-2014, 05:52 PM   #10
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Quote:
Originally Posted by CaseyJones View Post
So many things can cause that kind of noise. None of them are good. I agree with bashcraft for starters. If that checks out, I would have to think that you have a bad rod or main bearing. Automatic or manual? The thrust bearing clearance could cause the crank to "walk" in the saddles but that would be worse with a manual.. Is there any movement at the front, such as the balancer? Can you see it moving in and out ever so slightly at idle?

I was given a forged crank when I was building my engine that came from a truck. I was really good looking until I started looking at the thrust bearing surface. There was significant wear from pushing the clutch in over the years wearing the crank badly. So I didn't use it.

Do not see any movement at he front end of the crank.

This was built for me at a engine/motor rebuilder in St George, Ut.
Not saying it was a bad job but mechanical things do not always go as planned.
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Old 07-24-2014, 05:54 PM   #11
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After I talk to these guys I post results.
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Old 07-24-2014, 06:03 PM   #12
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Quote:
Originally Posted by MelWff View Post
What i was asking was are you sure the noise isnt from the distributor?
We thought it may be that the pump being new and distrib. old may be worn, but the distrib. is meshed with the cam gears. so for it to make a knock sound it would have to hit the pump slot but the what would cause the cam gear to run halted 3 x's the pause and again 3 x's and pause. There would be a noticeable miss running of the motor if the ditrib, was out.

thanks
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Old 07-26-2014, 01:16 AM   #13
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Up date on knocking.....not pump, found metal flakes in valley....motor goes back to builder...
Click the image to open in full size.
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Old 08-11-2014, 06:28 PM   #14
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Update: turns out to be flat cam...Now we deal with COMP CAMS warranty.
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Old 08-11-2014, 06:28 PM
 
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