spun bearings - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 25th, 04, 02:57 PM Thread Starter
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i bought a 454 bbc. someone correct me if im wrong but i think its a gen V or VI. it has no fuel pump provision. anyway, i bought the long block for $300.00. the guy said it was a spun bearing and when i took it apart, there were a couple of spun bearing. can someone tell me the causes of spun bearing? too tight? too loose? no oil pressure?

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post #2 of 13 (permalink) Old Mar 25th, 04, 03:41 PM
 
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I have heard that you can get them from grit behind the bearing- not giving it enough bite on its backing. If you've got two doing it, maybe it is something else.
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post #3 of 13 (permalink) Old Mar 25th, 04, 07:03 PM Thread Starter
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i think the guy who rebuilt it just put in the wrong size bearings.

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post #4 of 13 (permalink) Old Mar 25th, 04, 07:49 PM
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main or rod? could be a few things, if rebuilt, that just adds to the number.
also, another frequent cause of spun bearings is detonation. just have it all checked when it gets machined, and you'll be fine.
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post #5 of 13 (permalink) Old Mar 25th, 04, 07:51 PM
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Did the bearings truely "spin" in the block, causing the locating tangs to be wiped off, or is the surface of the bearing abraided and scratched?

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post #6 of 13 (permalink) Old Mar 25th, 04, 07:59 PM Thread Starter
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the block is in my shed right now but if i remember correcty, the tab on a couple of them are now flush.

angel

oh, and the guy said block was rebuilt by him. he didnt look too much like the maticulous(sp) or detailed kind of guy. he kind of looked like the kind of guy who would reuse plestigauge(sp).

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post #7 of 13 (permalink) Old Mar 25th, 04, 08:26 PM
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Quote:
Originally posted by angelglo:
he kind of looked like the kind of guy who would reuse plestigauge(sp).
It's not reuseable

Angel;
Hard to say exactly but if the bearings tabs have been wiped, then it's usually assembly issues (not enough clearance) or pre-lube failure on a new engine and lubrication (or lack of same) problems on older in service motors that lead to this.
Could be a very easy fix if the motor was fairly new and just put together crapy.
Tear it down and measure is the only way to see what needs to be done.
Block may need attention if engine was run very long in this condition.

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post #8 of 13 (permalink) Old Mar 26th, 04, 03:35 AM
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Quote:
Originally posted by angelglo:
he kind of looked like the kind of guy who would reuse plestigauge(sp).
Now that was funny

Spun bearings are usually caused by something being out of round, too tight, too loose, etc IMO. While lack of oil is often blamed, the root cause is usually clearances because you need proper clearance to get proper oiling.

Just my opinion.

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post #9 of 13 (permalink) Old Mar 26th, 04, 06:04 AM
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Eric has a good point about the "out of round", that I failed to emphasis, but falls into the 'assembly issues' area.
Most machine shops can get things pretty round - it's the way the machine tools are designed to work normally. The parts really should have been machine right - but, '$hit occurs'. The problems should have found during pre-assembly checks.
According to bearing manufacturers, the majority of bearing failures are caused by installation issues. I worked on many "come-backs" during my wrench-twisting-days that were directly traced to grease,chips,dirt & etc. being trapped between the bearing shell and the block bore (or rod bore)causing the bearing crush to be wrong and the bearing to be deformed at assembly. This type of failure was way more common than the bearing size being wrong. Many of these types of problems will not show up with the standard 'plastic-gauge' checks, only good measurements and assembly technique can prevent them. If you see your machinist/engine builder useing only 'plastic-gauge' during his "blueprinting" of your block - grab everything and leave. IMHO of course.
Long way of saying the 'out of round' is probably on the bearing side of things, not the crank or block bores.
If, as Angel says, 'the guy threw the thing together' and didn't keep every thing clean the problems may be slight - but, only carefull attention to measurements will be able to tell. If that motor already needed rebuilding prior to you getting it - chances are it lead a hard life anyhow, them things aren't all that old yet.
Best of luck with the block - let us know what you find as you tear into it!

ps: Never ran into a problem with bearings being 'to loose' at install and causing a 'spun' bearing - just "hearing loss"

(sorry so long)

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post #10 of 13 (permalink) Old Mar 26th, 04, 12:59 PM Thread Starter
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im going to be taking everything (block, rods, pistons) to baca's machine shop over here in south san francisco. they do all my machine work for all my motors. im just going ot have them check everything. i was just curious to see what kind of circumstances cause spun bearings. i actually never had that problem on any of the motors that i had put together. thanks for the responses guys.

angel

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post #11 of 13 (permalink) Old Mar 26th, 04, 01:38 PM
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It's been my experience that it's often low oil level/ lack of maintenence.

In the 80's, I made a career of replacing Fiero engines with spun bearings/rods sticking out of holes in the block. [img]graemlins/clonk.gif[/img]

[ 03-26-2004, 04:50 PM: Message edited by: ZZ430DropTop67RS ]

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post #12 of 13 (permalink) Old Mar 27th, 04, 05:04 AM
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Hey Don Just looked at your link, very nice 67!! and its the right color! [img]graemlins/thumbsup.gif[/img] .

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post #13 of 13 (permalink) Old Mar 27th, 04, 06:59 AM
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Thanks Bud, it's a lot of fun.

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