main bearing problems

lSyclonel

lSyclonel

Member
ok i have had two motors go bad cuz if the middle main bearings are being destroied when i get up in the boost. even the copper tore off the bearing, but the front and back are in great shape. now i know that the middle two bearing caps move a little with the 2 bolt main, and i can see that with the transfured metal on the caps and the block. but that does not explain the bearing going bad(wasted) in one afternoon.


I want to know from everyone that has had this problem, what they have done, how it is doing for them, and if they have taken a motor apart again and looked at them to see how they have woren?


Thanks
 
S

skata

Donating Member
yup, happened to me too.
with less than a 1000 miles on my motor(mostly freeway from pickin truck up), the engine developed a slight knock so i tore it apart and found my middle two lower main bearing halves were worn down to the copper.
the previous owner had just rebuilt the motor, and he used a regular 4.3 block and main caps. i wonder if the caps had anything to do with it. maybe the caps were shifting slightly under load?? maybe there was a lack of oil to the main bearings??
i would like to know what causes this type of wear.
 
lSyclonel

lSyclonel

Member
i know both of my engines had sy main caps on them. but still y does it happen is the million dollar Q?

Help us.... :x
 
jwaller

jwaller

Evil Genius/SyTy Guru
well y. can be answered in 4-5 different ways. oil problems. bolt problems, cap problem, detonation probelms, crank issues. and HP problems.
 
lSyclonel

lSyclonel

Member
well i know its not oiling problem, or stud, or detonation or crank issues. i think it is hp. and if it is, does 4 bolt mains work most of the time?
 
ed hess

ed hess

race or get outta the way
fwiw

did you guys use plastigauge to check bearing clearances while assembleing?

I also checked using an electric snap on torq wrench that as each cap or journal went on, the torq to turn the crank over was the same for each cap as they went on.
did you do this as well?

ed
 
S

Sy#26

New member
When my built 4-bolt mains engine spun the center two main bearings, the builder (UltraTech in IN) put upper bearing shells (grooved) on both the top & bottom of the mains. Theory being to assure max lubrication of the lower, although you do lose some bearing area. Might be something to try.
 
T

TyMeUp

New member
A new GM long block installed into a '93 Typhoon by a GMC dealer spun the center main with less than a year of non-abusive use.

After talking to the service manager and technician, I'm thinking they never 'prelubed' the engine before the first startup. "The factory does that before they ship it" ... IS NOT CORRECT.

A different GMC dealer did the warranty replacement. This dealership's technicians know that you have to use an old gearless distributor stub to drive the oil pump for several minutes before a first start.

Also, when doing an oil change on any turbo engine, it's good practice to fill the oil filter before installing, then disable the ignition and crank the engine for 15 seconds before actually starting it. After starting, leave the engine idle for a while before reving.

If you are using a 'Qwiky Oil Change' service, make sure you specify that this is how you want it done on your vehicle. If they refuse because "it takes too much time" - go elsewhere.
 
nightdiver

nightdiver

Active member
I had the same problem .....it was the oil cooler.....full of shit,even filter paper inside.
I bought a BIG high flow oil cooler and im :D
 
S

skata

Donating Member
nightdiver said:
I had the same problem .....it was the oil cooler.....full of shit,even filter paper inside.
I bought a BIG high flow oil cooler and im :D
Click to expand...
damn, it sounds like the mains are a common failure :evil: , along with broken cranks. :roll:
i didnt even have a oil cooler connected. i had a filter right on the block so i dont think oil starvation would have caused the failure. unless there are some oil passages or restrictors that need to be modified to push more oil to the main bearings.
 
lSyclonel

lSyclonel

Member
well i did some reserch on bearing. a brand name called KING. they are a newer company. the lower part of the main bearing have the oil grove(like the top one) on the sides of them and then tapers off to the flat bearing.i think im going to try them ones next.

so it sounds like even 4 bolt mains have the same problem too?

ill put pics of my bearing on tomorrow.
 
Don W.

Don W.

Stab it and steer it
FWIW…

Haven’t read the posted web site yet but like others have said; One thing I -always- do on a fresh rebuild is roll the motor with the starter until I have oil pressure. I do this -without- the plugs so there is minimal load on everything. Usually only takes a moment. This way everything is primed. If nothing else I sure feel better.


Don
 
bezerk

bezerk

New member
I have the same prob with my 800 Mile engine.
i have a brand new engine, so first there was a slight knock. but after doing oilchange (with grey tinted-oil), the knock was becoming louder, so i pulled the engine today and i than i saw it, the bearing rotated so itcouldn''t get lubrication, . i think it was a mistake by a GM mechanic.
tobad i didn''t buy it at a shop.

it''s the bearing from crankshaft to pistonrod

atleast i know to pull the engine FAST

2bolts
 
nightdiver

nightdiver

Active member
Rene, i see we all learned the same way
I had crankshaft lubrication problems when i first bought the Sy 7 years ago :-? then i overboost and brake two pistons :-?
After this i did the repair(s) alone and i didnt have problems any more 8)
 
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