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Discussion Starter #1
I was doing some work underneath my Camaro last night. I replaced the transmission mount, adjusted the shifter, and fixed the speedometer cable. After I got done, I took it out for a test drive. Everything was much smoother but there was still a high speed vibration in third and fourth gears. Anyway, when I got off the highway, I heard a slight knock in the engine. It still runs smooth, but there is a slight knock in the right side of the engine. It isn't there when it is cold, only when warmed up. The only time that you can hear it is when the RPM are going down. When you hold it at a steady RPM or the RPM is going up, you can't hear it. It is definitely in the lower end of the motor. Do you think that it is a Rod or wrist pin. I noticed no loss in oil pressure, but it never held much anyway.

The engine is a 400 small block that I rebuilt about a year ago. I thought that I did everything right. All bearing clearances were right on the tight side of the tolerance. I used a cast crank that I had polished. My machinist said that it was alright when he checked it for straightness and everything else. I cleaned everything thoroughly (at least I thought I did). I thought that I did everything right. Oil pressure has never been really good. I always thought that it was the gauge. Right now, I have about 10-12 psi at idle and about 40psi at 2800 RPM cruise with 0W/30 Amsoil. Its been like that ever since I put the gauge in about 10 months ago. I didn't notice any loss in oil pressure. I am going to cut open the oil filter tomorrow. Hopefully that will let me know more. Do I have a rod knocking? How could I tell for sure?

Also, if it is a rod bearing, will I have to replace the rods? What could have caused this?
 

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I think the only way to be certain is to drop the pan and look at the rod bearings by removing the caps one by one. I know, that's a ton of work which basically means pulling the engine. Causes of rod bearing failure are many. If used rods were utilized I suspect they were not resized properly. Sorry to hear that your rebuild has problems.



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Joseph

1969 Camaro
404 SB w/ 10.3:1 Eagle 4340 assembly in Dart Little-M block, AFR 210's, Crower #00350 short track solid cam 238/244 @ .050" on a 107 lobe center and .530" lift w/ 1.6 rockers, Holley 750 vac sec, Victor Jr., custom 1.75" headers, Spintech 2.5" exhaust with x-pipe and Sportsman XL mufflers, T-56, CenterForce Dual Friction clutch and billet flywheel, Guldstrand Mod., Landrum 600# front springs and adjustable spacers, Hotchkis 1.125" front bar, Detroit Eaton 175# rear springs, Bilstien shocks.
1971 Ford Bronco
Stock 302, 4" rock crawler suspension lift, 1.5" body lift, NP435 tranny, 4.11 gears, Detroit Locker rear diff., Power-Lock limited slip front diff., 33" BFG MudTerrain tires.
 

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is this a new noise or is it forged pistons slapping when cold. to find the offending cylinder pull the plugs one at a time till the knock quits. also a small block only needs 10 lbs for every 1000 rpm. in your rebuild did you use the corect oil rod for a 400 not the same as others will put metal in the motor. moroso sells a nice screen that fits over the top of your filter an realy shows you whats in the oil. good luck let us know
 

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Discussion Starter #4
This is a new noise and hypereutectic pistons were used instead of forged ones. I got the oil pump driveshaft from my machinist. Surely, he gave me the right one.

Rods were all resized and ARP wave lock bolts installed by my machinist. I checked the bearing clearance on all journals and they were all right on the lower end of the tolerance. This motor was tight, maybe too tight.

If I go in and replace the crank, rods, and bearings, will I have to rehone the cylinders? If I rehone the cylinders, will there be too much clearance between the cylinder walls and the piston skirts?

[This message has been edited by Cameron (edited 08-19-2002).]
 

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forget the piston slap no noise when cold, but when you slow down? flex plate cracked? easy to check an will cause vibration.
 

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Discussion Starter #6
Storman,
I have a manual transmission. Could something be loose or cracked at the flywheel?
 

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Couldn't it just be a bad lifter? What lifters do you have? A lifter would knock at half the speed of a rod, so listen carefully. I had the same problem once and it turned out to be a lifter, it was much less when i changed to synthetic oil. Just a thought...
 

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Discussion Starter #8
I don't believe that it is a lifter. Lifters usually make a light tapping noise at half the speed of the engine. This is at the same speed as the engine and it sounds as if it is coming from the lower end of the motor.
 

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I have read that if you don't polish a cast crank the same way it spins, you can create a very slightly rough journal surface that under a microscope looks like "fish-scales" pointing in the wrong direction. And this microscopic scale looking surface will eat a set of bearings real quick!! pdq67
 

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Discussion Starter #10
I just got done tearing open the oil filter. Here are some pics of what I found.
http://cards.webshots.com/c32299639bfzbmk
http://cards.webshots.com/c32299666qftbbc

It appears to be a brass or copper material. Does this look like a bearing to you all?

Also, have any of you bought crankshaft kits from Advance Auto Parts? Are they any good?

[This message has been edited by Cameron (edited 08-20-2002).]

[This message has been edited by Cameron (edited 08-20-2002).]
 

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just saw pics, doesnt look good wish i could see them better awful big for bearings. wouldnt run it again time to pull the pan but i think i would pull valve covers an intake first. the correct oil rod for a 400 is tapered halfway down or so not same diameter all the way. let us know good luck
 

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Pull your distributor and see if you have a bronze gear. That is the only thing in the motor I can think of that has a gold color. Considering the size and quantity of the material in the filter I would check all bearings and cam, basically total tear down. Lots of work but needs to be done. IMHO.

Joseph
 

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Discussion Starter #13
Yeah, the motor is coming out. I just took the metal particles to my machinist. He didn't know for sure, but it looked like a thrust bearing to him. He also said that if a rod bearing has let that much material go, it would be very loud. I tend to agree with that. I don't think that my Mallory Unilite distributor came with a bronze gear. I will check on that when the engine is apart.

Also, its hard to tell from the picture, but the particles are more copper or maybe bronze colored than gold colored. It looks like little copper shavings.

Anyone else have an idea of what has happened?
 

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I seriously boubt that much material came from a bearing. The size of the pices are just too larg. If that was a bearing I think you wouldn't be wondering if it was a knock (you would hear it loud and clear). It could very well be the thrust surface of your ream main bearing, this would aslo explain why you hear it when decelerating. You don't have roller rockers do you? If so I would have a good look at the underside of them, could be rubbing on the valve spring. As far as your oil pressure you are fine, especially with 0-30wt. Another reason I doubt it is a bearing. In either case sorry to see you have trouble, I just hope it turns out to be minor.

Royce

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70 Camaro 385ci
69 Camaro (soon to be 6" rod 355 backed by a T56)
2000 GMC Z71

http://hobbystage.net/camaro/camaroman7d/
 

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Discussion Starter #15
Camaroman,
I hope that is all that it is. I am going to pull the motor out this weekend. I do have roller rockers, but I don't think that they are rubbing the valve springs. I will check it out when I disassemble the motor. I'll let everyone know what it turns out to be.

Another interesting thing that my machinist said today was that if a motor is going to spin a bearing or have some other major failure, it is usually going to do it within the first 1000 miles or so. My engine has about 6000 miles on it.

If it turns out to be the thrust bearing, what will I have to do to ensure that this doesn't happen again?
 
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