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400 sbc thurst bearing

 
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96911ss
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Joined: 30 May 2006
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PostPosted: Thu Jun 01, 2006 4:59 pm    Post subject: 400 sbc thurst bearing Reply with quote

Hello, thanks for the help with the 350 balancer. My 400 SBC the thurst bearing keeps coming apart and rest of the main bearings look badly worn, only after 30 miles driving time. Motor runs strong and does not seem to viberate. This is the second time it has happen to this block. Two different builders?? The second time it was built, went to bolt on oil pump, threads broke out, drill and tapped and installed heli coil. I didn't drill all the way through bearing cap, left about 1/8 untapped from bottom of hole. Leaks oil bad at rear seal. Did install oversize rear seal, since it was line bored. Bearing have about the same damage both times built. It has stock 400 crank 5.7 powered rods wiseco pistons flat top two valve relief. Zero deck clearance, line bored. Two bolt main block. Heads are alumium holley. 284 extreme cam.
aftermarket 400 balancer. The car is a 4 speed manuel. 350 flywheel with bolt on weight. Thanks
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bill jones
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Location: Salt Lake City Utah
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PostPosted: Thu Jun 01, 2006 5:50 pm    Post subject: Reply with quote

-is it the rear of the rear main bearing that is wearing out?

-Does the front of both the rear main bearing thrust flanges look good?

-Are you assembling the rear main and adjusting it rearward while holding the crank forward? so that both of the rear thrust flanges are right up against the crank flange?

-Has the thrust clearances been checked without the rear main cap installed? and then rechecked after the main cap is torqued up?

-Have you checked to make sure you have this same final endplay number AFTER you install the engine? to prove that the trans snout isn't bound up against the pilot bearing?

-Is either or both of the flanges of the crankshaft damaged and galled from the problem?

-----------------------------------------
-Are you having someone else repair this or are you doing it yourself?
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Thu Jun 01, 2006 6:00 pm    Post subject: Reply with quote

Who put the motor together? Sounds to me like it could be a combination of problems including all o the above mentioned and probably more....
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jeep_406
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Location: Tewksbury, Mass 01876
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1972 Chevrolet Nova

PostPosted: Thu Jun 01, 2006 7:43 pm    Post subject: Reply with quote

Did you assemble the engine?
If you had it align bored and put the caps back right and everything miked up correctly I'd check to see if the crank is straight.
On #5 you didn't use a bolt to hold the oil pump that was too long?
Does it seem to be lack of oiling or possibly dirt or other contamination?
Everything cleaned properly?
Were the oil gally plugs were removed during the block cleaning?
No chance that glass bead was still in the engine? That will kill an engine very quickly.
Did you run a 350 balancer on the 400? Going that quickly you should see something.
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96911ss
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PostPosted: Thu Jun 01, 2006 7:43 pm    Post subject: Reply with quote

HEY ,bill thanks for the reply.
1.The whole rear bearing is wiped out.
2.back flange as alot of wear.crank seems fine
3.2 differnt people has built this engine,same results.i am not one of them.Both are good engine builders
4.I built a 350 to go in the car using same trans.no main beaing damage.but the no 4 rod bearing wiped out.
5. i have built two different 350 for other pepole since the 350.no problems.i think this camaro is from hell.that may be why it sat for 20 years.i just keep having bearing issue with this car.some times i thinkl it is the trans but it works great.
6.How can i make sure the stout is not binding in the poilt bearing?
7.the stout does have a small amount of polit bearing resuidue on it.Thanks
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jeep_406
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1972 Chevrolet Nova

PostPosted: Thu Jun 01, 2006 7:47 pm    Post subject: Reply with quote

Did the tranny bolt right up or did you have to bring it in with the bolts?

How heavy a clutch pressure plate are you using?

Did the engine turn over any differently before and after you installed the oil pump?
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96911ss
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PostPosted: Thu Jun 01, 2006 8:50 pm    Post subject: Reply with quote

Hey jeep406,i did not build engine.But everything looks clean.it is a after market balancer with a bolt in weight.pressure plate is a ram unit.Just a little better than stock.
1.When i installed the engine the 2nd time,the trans was in the car bolted to the bell housing.i did use the bolts to pull it up.it was an easy pull up.i did not have to force it.
2.i did not tap the bearing cap oil pump hole all the way though.so bolt did not hit bearing.
3.I would think the crank was checked for strightness.sounds like a possiblity.thanks jeep 406
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bill jones
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PostPosted: Thu Jun 01, 2006 10:15 pm    Post subject: Reply with quote

-YOU have to take a certain amount of responsibility here and get the tools to check the endplay---then know the numbers before you bolt the transmission up to the bellhousing.
-There are MANY problems exactly the same as yours where the transmission or clutch or the torque convertor binds up at the rear of the crank and forces the crank forward way too tight against the thrustr bearing.
---------------------------------------
-The simplest test is to get a log pry bar in the front AND in the rear and see if you can click the crank back and forth.
-you should be able to FEEL it----and with a dial indicator you should see about .004" to .008" of positive front to rear---or----rear to front movement using the pry bars.
-It doesn't take a lot of pressure on the pry bars either---you should be able to easily click the crank back and forth.
----------------------------------------
-Once you have established this endplay with the transmission not bolted up---then when you install the trans--- before you EVER rotate the engine----you need to step in on the clutch one time with the transmission in high gear and have some one under the car try to rotate the drive shaft by hand.
-It would be best if the driveshaft was not connected to the rear end at this point.
-If it doesn't want to rotate this is the first clue you have a problem of the transmission bound up----so if you then loosened the transmission bolts---stepped in on the clutch again and had your helper trying to rotate the driveshaft and you find that now you can rotate it----then you need to find out what is binding.
------------------------------------
-Typically the first place to look is the pilot bearing may not be pressed into the crank far enough.
-----------------------------------------
-I would be suspecting that the 350 flywheel and the bolt on weight could have something to do with the problem.
-If the bolt on weight fits onto the crank and then you install the flywheel where the weight is sandwiched in there----that would move the flywheel and the clutch closer to the transmission so the clutch hub might be binding at the rear of the trans snout splines where the splines are tapered out to the OD of the shaft.
-Maybe the clutch disc is installed backwards---I don't think that could happen but it's something to double check.
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96911ss
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PostPosted: Fri Jun 02, 2006 7:00 am    Post subject: 400 sbc thurst Reply with quote

Thanks bill jones for all your help also jeep 406.I am going to ckeck all these things.I will let you all know results.Thanks
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Big Dave
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PostPosted: Sun Jun 04, 2006 11:32 am    Post subject: Reply with quote

My knee jerk reaction is pilot bearing also. I'll wager trans is pressing on back of crank and is the cause of failure.
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af2
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1933 Willys Coupe

PostPosted: Sun Jun 04, 2006 6:10 pm    Post subject: Reply with quote

Big Dave wrote:
My knee jerk reaction is pilot bearing also. I'll wager trans is pressing on back of crank and is the cause of failure.


I have read this post many times to try and think what can cause this. #1 you should always be able to slide the transmission in completely without using the bolts to push it in. I have cussed to many times loosening the clutch and realigning it so that happens. Usually the Damned thing falls into place when you flat gave up and feel like arm strong. The only other thing I can see that if the front of the thrust is damaged someone beat the balancer on instead of pulling it on with an installer. On other thing that is important is before you set the torque on the rear main bearing that you give the crank a tap to align the two bearing halves so you don't have one scraping and one galling the other one. That will kill the thrust bearing in a hurry with a clutch.
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