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AK427
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794 Posts
Discussion Starter · #1 ·
383 SBC, just changed oil pump and pan. Was running perfectly prior to this.

When I crank it over on the starter, everything sounds normal... oil pressure comes up nice and quick (50psi cranking pressure). BUT, when the engine fires, there's a very loud clattering noise from the bottom half of the motor which increases with RPM. Oil pressure was fine for the couple of seconds I had the motor running.

I was thinking maybe the crank throws are hitting the pan (definitely sounds like something hitting something)? It's a Moroso pan which has mini scrapers built-in, but it's supposed to be good for a 3.800" stroke (I'm running 3.750"), so it should be OK?

If the crank was hitting, is it feasible it would only do so when the motor is actually running rather than being cranked on the starter?

Any other ideas?

Oil pump is a Melling Select std. volume, high pressure.
 

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AK427
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794 Posts
Discussion Starter · #2 ·
I should add the pan has mini scrapers built-in, but it's my understanding these do not need trimming to fit (unlike full size regular scrapers).
 

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InDeep****Now
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49 Posts
Any other ideas?
Well, when my motor was built, I ran it immediately at high performance settings, timingwise. What happened was, that caused too much pressure on the crank during break in. In turn, it split the crank caps in half, and destroyed bearings... I also have a high volume oil pump installed. In your case, I'm sure there is a difference between scraping sounds, or just plain racket noise... Scrape sounds would be timed. I mean, you would be able to tell. Random noise and racket is not good. Oil pressure issues, and noise indicate crank issues to me. But then again, I'm no super mechanic. Just saying from my experience. Maybe your best bet would be to pull the pan to inspect for signs of scraping. When changing the oil, I would look for shavings as well. Hope this helps.
 

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AK427
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794 Posts
Discussion Starter · #4 ·
Well, when my motor was built, I ran it immediately at high performance settings, timingwise. What happened was, that caused too much pressure on the crank during break in. In turn, it split the crank caps in half, and destroyed bearings... I also have a high volume oil pump installed. In your case, I'm sure there is a difference between scraping sounds, or just plain racket noise... Scrape sounds would be timed. I mean, you would be able to tell. Random noise and racket is not good. Oil pressure issues, and noise indicate crank issues to me. But then again, I'm no super mechanic. Just saying from my experience. Maybe your best bet would be to pull the pan to inspect for signs of scraping. When changing the oil, I would look for shavings as well. Hope this helps.
Oil pressure is fine. The noise isn't random, it's a rythmic knocking sound.
 

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Hotrodders.com Moderator
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2,100 Posts
You would think you'd hear it while cranking but the windage of the assembly moving might be enough to move things enough to hit.

Check the scrapers for contact and look at the sidewall of the pan near where the oil filter is. Two common spots for contact.
 

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Registered
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Moroso oil pan

I bought a Moroso oil pan for my big block chevy. I was telling my machinist about it. It has the wire windage tray and crank scrapers. He told me that most people he has dealings with remove the wire screen and crank scrapers because of the crank hitting. I didn't remove mine and had trouble with the crank hitting. I removed the pan and used a round piece of pipe to beat the screen down some in the area below the crank scrapers until it didn't hit anymore. If I have anymore problem with it I will remove them and chunk them in the trash. It will still have the trap door baffling.
 

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AK427
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794 Posts
Discussion Starter · #9 ·
You have the right pump. Did you turn this over by hand before you fired it up? You put a steel pump drive in? Like a Moroso one, Clearanced for a 383?
Now pull the pan back off and see what went wrong.
Didn't turn over by hand... turned on the starter (which it does fine with no unusual noises). Pump drive is the steel one supplied with the pump. Like I said, the pan is supposed to be good for 3.800" stroke.
 

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http://www.warsprints.com
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2,024 Posts
I personally would not have installed a high pressure oil pump, high volume maybe. The stock pump is all you need. High pressure pumps are used when bearing clearances are excessive to reduce friction for drag racing. Something is going on with the new pan. All you can do is remove it and see where it's been rubbing on the crank and remove the culprit.
 

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Hotrodders.com Moderator
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6,391 Posts
If you crank it and put a hand on the pan you should be able to feel it if is it hitting. Just disable the ignition so it wont start.
 

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Well first I have to say I would not suggest your oil pump choice hi-pressure, or hi-volume, at higher rpms you will start having oil leaks and they have a tendency to push all the oil to the top of the motor and start cavitating which sooner or later will cause engine damage, as far as the pan either your connecting rods are hitting your scrappers or the counter weights are moroso may say no trimming required but from experience every time I have used anything from them dealing with oil pans windage trays etc. I have had too trim or modify it in some way or another
 

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More for Less Racer
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21,107 Posts
Pan may be listed as clearing 3.800" stroke...but it can make a difference what the shape of the big end of the rod is.

Also, manufacturing mistakes do happen.

You're going to have to pull the pan and verify clearance with the complete rotating assembly.

As you well know...with aftermarket parts, installer is responsible for confirming fit, not the manufacturer.:rolleyes:
 
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