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#1
08-29-2019, 08:03 AM
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Number 4 Rod bearing
Had number 4 rod bearing fail. All other rod and main bearings look like new, even number 3. Engine is a year old with roughly 80 passes. All lifters look like new as well.
Any suggestions on where to look. Oil pressure and clearances are in check. |
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#2
08-29-2019, 08:07 AM
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get the rod checked...
__________________
My Half AN Injun..... |
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#3
08-29-2019, 09:18 AM
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#4
08-29-2019, 09:45 AM
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I would have that rod checked for size. It may be too tight.
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#5
08-29-2019, 02:54 PM
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A few pics would be helpful. What I would like to see is the bearings and also a pic or two of the rod big end looking at where the bearing sits.
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#6
08-29-2019, 10:26 PM
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Any signs of detonation in that cylinder? That will pound the snot out of a rod bearing.
Is the bearing cracked and spalled (fatigue), wiped (ran dry), blackened (not enough oil to keep it cool)? Other? Eric
__________________
"Everybody has a plan until they get punched in the mouth" noted philosopher Mike Tyson Life begins at the end of your comfort zone. The mind, once stretched by a new idea, never returns to its original dimensions. |
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#7
08-29-2019, 11:39 PM
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Are you main bearing the Clevite style ? If they are they need drilled to match the hole coming from the tab side of the block. Race bearings have a slot and do not need this.
Whittmore told me I would loose either # 4 or #6 rd bearing if I did not do it. |
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#8
08-30-2019, 03:08 PM
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Clevite Chev rod bearing with 3/4 groove FM main bearings
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#9
08-30-2019, 03:23 PM
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[ATTACH][ATTACH][ATTACH]
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#10
08-30-2019, 04:06 PM
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Are you positive the upper and lower halves were in the right orientation? looks like the one in the second picture is hanging over into where the radius of the crank is.
__________________
66 GTO Nostalgia Super Stock/Street Legal Car 421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99 Multiple NSCA/NMCA World Champion 66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles 67 GTO 2dr Post, 428, Tri Power, 3.55 Gears 80 Trans Am Black SE Y84 W72 WS6 |
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#11
08-30-2019, 08:00 PM
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The piston pictured looks completely different from the one on either side. Did you clean the piston head in that cylinder? If not, something was going on in that cylinder. If ring lands are pinched and oil has made it's way to the top, detonation follows quickly and kills the bearing. However, looking at the bearing, it looks like oil starvation, so not sure without some more info and pics. Don't want to guess. Could you post a few pics of some of the other rod bearings for comparison? Thanks
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#12
09-03-2019, 07:53 AM
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The top of #4 piston is cleaner than the rest. The picture shows what it looked liked when the head was removed. The #4 combustion chamber is cleaner that the rest as well. The center face of the intake valve is bare and clean about the size of a dime and the machined pocket in the head is bare and clean as well adjacent the intake valve.
I am leaning toward a ring problem in that one cylinder that may have caused the rod bearing to go. Bearings were put in correctly. |
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#13
09-03-2019, 08:23 AM
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Was water getting in there. Check the cylinder wall for a crack or head gasket for a leak.. maybe check the head for a crack as well...
__________________
My Half AN Injun..... |
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#14
09-03-2019, 08:37 AM
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Quote:
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#15
09-03-2019, 10:02 AM
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Will do, that makes the most sense.
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#16
09-03-2019, 10:22 AM
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I think the piston is clean because the bearing was wearing out making the piston hitting the head. (or very close)
I'd check the crank holes and block holes for obstruction? What was the clearances on rod bearings? Also were the bearings for big chamfer on crank? 
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." Socrates |
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#17
09-03-2019, 10:42 AM
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__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." Socrates |
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#18
09-03-2019, 10:48 AM
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You may be right, but I would think there would be combustion deposits from before. Have 0.036 deck clearance. Pistons are at zero deck with a 0.036 head gasket. Pistons are flat tops. Rods 0.0025.
Engine ran fine on the dyno and for about 80 passes afterwards. Then slowed down all of a sudden. I have a System One oil filter which I take apart on a regular basis. Did not show any debris until the last weekend out. Car was fine on Saturday and first two passes on Sunday then slowed 0.06 on the next pass then slowed up again the next pass. I then parked it to determine the cause. Pulled the filter apart and found debris, which lead to taking the engine apart. Going to go through it all before putting it back together. |
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#19
09-03-2019, 11:53 AM
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What block do you have?
Did oil pressure drop on run? Possibly block cracked from main to cam bore (along oil passage) if stock block?
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." Socrates |
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#20
09-03-2019, 11:58 AM
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MR-1 block.
Did not notice oil pressure drop, however I do not have a data logger. I do run an accumulator. |
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