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Old 10-07-2008, 10:36 PM
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thrust bearing out on new 406 build

i had a guy that does work out of his garage build the short block and he put in the arp main studs and line board it. he had this brand new machine and he told me that is was so precise that it did not need to be honed. and i am thinking that this might be my problem. what do you guys think?

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Old 10-08-2008, 08:31 AM
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You think this might be your problem with what??
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Old 10-08-2008, 08:40 AM
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Quote:
Originally Posted by 694X4
i had a guy that does work out of his garage build the short block and he put in the arp main studs and line board it. he had this brand new machine and he told me that is was so precise that it did not need to be honed. and i am thinking that this might be my problem. what do you guys think?
I am assuming he has a dedicated line-boring machine designed to properly do automotive engine align-boring. If this is the case, one can do what he says, although most shops will align-bore, and then align-hone to final specs.

Most guys working out of their garage don't buy brand-new align-boring machines.

It is possible that thrust cap was cut improperly, which can cause thrust bearing issues.

It is also possible that the thrust bearing was not installed correctly or the transmission has too much line pressure or the torque convertor was not seated properly (if an automatic was used).

tom
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Old 10-08-2008, 01:26 PM
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i pulled the oil pan this morning and pulled the main caps and all the mains are worn unevenly. one thing when i brought this block in it had the thrust out of it about .030 end play and now it is .028 the crank was brand new from scat when i got it back end play was good within spec. every thing on the trans was almost new and lined up good just under 1/4" gap in between torque conv and flex plate. if it was the conv ballooning the wear would be mostly on the back side of the thrust i would think and it seems to be equal wear on both sides. the machine he had was not a dedicaded to just line boaring it would do just about every thing with diferent atachments. i just never heard of just boaring a block without line honing it but he ashured me that it would be good. i just wanted to get mor info on what other people thought with engine building experince thought before i bring it back to him. and this seemed to be a good place to get advice.
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Old 10-08-2008, 02:01 PM
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It's kind of like in health problems, if you don't like OR trust your doctor you get a second opinion. Before I took the block back to this guy I would go to a real machine shop and pay them to diagnose the problem. If they can and the block is salvagable then I would have THEM fix it.
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Old 10-08-2008, 02:15 PM
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Quote:
Originally Posted by 327NUT
It's kind of like in health problems, if you don't like OR trust your doctor you get a second opinion. Before I took the block back to this guy I would go to a real machine shop and pay them to diagnose the problem. If they can and the block is salvagable then I would have THEM fix it.
Ah ya, what he said.
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Old 10-08-2008, 02:37 PM
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Quote:
Originally Posted by 694X4
i pulled the oil pan this morning and pulled the main caps and all the mains are worn unevenly.............. the machine he had was not a dedicaded to just line boaring it would do just about every thing with diferent atachments. i just never heard of just boaring a block without line honing it but he ashured me that it would be good. i just wanted to get mor info on what other people thought with engine building experince thought before i bring it back to him. and this seemed to be a good place to get advice.

I'm very interested in knowing what kind of machine he is using. There are some very high-dollar machines that can do as you describe, but even those should be used in conjuction with an align-hone machine.

The uneven wear on the main bearing is a giant red flag.

As has been suggested, you would do well to take your block to another shop and have them check it out........

tom
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Old 10-08-2008, 03:02 PM
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Quote:
Originally Posted by 694X4
i had a guy that does work out of his garage build the short block and he put in the arp main studs and line board it. he had this brand new machine and he told me that is was so precise that it did not need to be honed. and i am thinking that this might be my problem. what do you guys think?
Whose crank? There's several on the market that do not put sufficient attention to the quality of their machining of the thrust faces.

Installation can also be an issue. The proper procedure is to start by installing the thrust main into the block and cap without the crank. Align the mating edge of the thrust portion on both sides so there is no step between these surfaces. Gradually pull the cap up to full torque and check as you go. On the Chevy,then install the oil pump and torque it's bolt to the crank and recheck the alignment. You're doing this now just to get a feel for the alignment which you can't see once the crank is in so this is the opportunity to correct any errors before installing the crank. Once this looks good remove the cap and drop in the crank, bring the mains up to torque, except the thrust main. Pull it up to about 10-15 ft lbs. Then with a large pry pull the crank forward and back a few times to locate the bearing so the gap between the top and bottom bearing halves is flush. Repeat this at intervals till the cap's fasteners are fully torqued. Anally retentive people will take this apart and check everything again before torquing up the bottom end and calling it good, but at this point it should be good to go. What can happen if you just put the thrust bearing in and torque it up, is there can be a step of miss alignment in between the top and bottom faces. This will wipe the oil off the surface and failure of the crank and or bearing will soon follow. don't forget to also check the clearance between the bearing and crank thrust faces as you do this.

Bogie
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Old 10-08-2008, 04:08 PM
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Quote:
Originally Posted by machine shop tom
I'm very interested in knowing what kind of machine he is using. There are some very high-dollar machines that can do as you describe, but even those should be used in conjuction with an align-hone machine.

The uneven wear on the main bearing is a giant red flag.

As has been suggested, you would do well to take your block to another shop and have them check it out........

tom
Most all machines i've ever seen are only as good as the operator....Take your stuff somewhere else as others have suggested!
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Old 10-08-2008, 08:02 PM
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Ok, first off a line bore, or hone will not affect the thrust main. Is is most often incorrect assembly. A 400 does not have the dowel on the rear main, so if you don't torque it up, seat it and retorque it, it's gonna fail. Secondly, use some punctuation man! It would be alot easier to diagnose your issue if it wasn't one big sentence. If you have "uneven wear" on the mains it's possible he over bored the saddles and the block is junk ( no crush, too much clearance). And what do you consider uneven wear? Do you see copper? Why did you pull it apart this time? Bad oil pressure, knocking, what the dilley, yo? How did you get to the .028 measurement? If you've had two thrust main failures with the same block, in the same car that is more than a coincidence.
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Old 10-08-2008, 08:27 PM
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Actually, what can and does happen very often when a block is align honed or bored, the caps mating surface to the block is cut crooked to the vertical face of the cap. No did deal on caps that dont hold a thrust bearing. But on the thrust cap, the bore can still be straight and on size, but the thrust face will not be 90 degrees to the bore,causing the crank thrust to only contact the thrust bearing on a very small area of the bearing face,as well as "pinching" the two halves of the bearing causing the I.D. to become distorted,easily causing it to fail! Most sharp machinists place a good "used" thrust bearing in the cap to hold it "square" in the cap cutter as it is being cut.
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