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Main Bearings # 2 and # 3

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Spooling

Member
Joined
May 24, 2001
Messages
271
Folks:

Finally got some free time to examine my hot oil pressure issue today, and it appears as if # 2 and # 3 Main Bearings got "wacked". Clevite-77's are shown in pics below.

Crankshaft looked incredibly nice - but the bearings definately took the hit.

Mains # 1 and # 4 were in very nice shape, as were ALL of the rod bearings - all 6 looked incredibly nice.

The sides of the Thrust Bearing displayed no visible signs of converter issues.

Engine has steel caps all the way across, and does an incredible amount of "sitting" in my garage.

Oil pump consists of GM front cover w/ 0.002" gear end play, stock length gears, glassbeaded w/ idler gear drilled w/ one 1/8" hole, KB Booster Plate, Bypass Blocked, "Biggie" Oil Filter Adapter w/ AC # PF-24 filter & Oil is Pennzoil 30wt + sometimes Prolong.

I slid some new bearings in today on both the mains & rods (FM's on the Mains & Clevite's on the Rods). Also went with an external oil cooler JIC after this episode.

Gonna prime the oil pump and see how it goes.

Regardless - I got another 109 Block in the works now - doing things a little differently this time.

My neighbor - whom builds some pretty BA Corvettes & has been a GM guy for ~ 20 years said the lower bearings definately took the "hit" and said they looked like they went through some continuous "dry" start-up conditions.

His analysis is true, as when I would start the engine - after extended periods of sitting - I could hear - what I thought were the rods "barking" for a few seconds until the O.P. Gauge came up.

Wondering if blocking the bypass could have something to do with this?

I have also seen the AC Delco filters appearingly "buckle" inside, yet, never come apart or blow out the seal and dump it's load - like I heard the small filters do.

Car will probably continue to sit in my garage for extended periods. Not excited about pulling the cam sensor & cranking the oil pump before starting each time. Is there a better way? Crank w/ ECM line disconnected until pressure builds?

Suggestions, Comments, Analysis - Thanks all.

Regards.

Edward
 

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Your oil pump should not be losing its prime. IMO that sounds like the issue here. Try another filter that has good anti drainback valve,WIX,Mobile one,Purolator...not Fram or Delco.

You can pull the ECM wire and crank until you see pressure for now.
 
Permanent fix is an Accusump pressurized oil reserve, I would definitely stay on the additive wagon for the "clinging effect which should help startup, other than that, dissconnect the ECM wire on startup so there is no load on the bearing until oil pressure is up, crank for 30-40 seconds, connect wire and fire up.

Has this block been "Hard Block" filled ?
I am pretty sure the cast iron wicks heat away more effectively than the billet caps, but that would be a long run situation.

I still run 15-50 Mobile one in the street car

I also am a firm believer in the missing zinc causing a problem, the 15-50 has the highest levels but still not up to the Rotella I run in my 489 BBC.
 
I would recommend using coated bearings. If it IS a dry startup condition coated bearing will help.

Mike Banas
87GN
 
I had the exact same problem as my car sleeps a lot. You were smart to pull it apart before it really got bad. I put new bearings and now I disconnect the orange wire till pressure comes up and no problems since. My bearings might have also taken a hit when the alky pump went out at 22 psi. The 2 center mains take more of the load than the outers.
 
I would check the bore housing size and main journal size. With billet main caps, you want to be in the mid-max end of the spec range. When bearing manufacturers design the bearings, they take into account the amount of cap flex. With stock caps, there is more flex than billet caps.

Also, mains 2 & 3 supply oil to rods each.

Billy T.
gnxtc2@aol.com
 
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