I lost the #6 rod bearing 40 miles after fresh rebuild?!

rking

Senior Member
Joined
May 30, 2001
Well guys, I finally hit some bad luck with these engines. I would guess that this one is at least the 30th turbo 3.8 that I have built, and have never had any oiling problems after a rebuild.

So the car had about 4 hours on the engine and about 40 miles of driving. Oil pressure was always at 80 psi cold, 40 psi hot. Took it out to get some pics and on the way home after casual driving, (seriously, casual and no boost), the oil pressure started to drop at idle to around 10 - 15. Made me worry but didnt think too seriously about it since I would be home in about 5 minutes. During part throttle the oil pressure was just fine. Pull it in the driveway and let it idle down, oil pressure goes to 0 :eek: !! I thought the gauge was screwed, so I blipped the throttle and BAM BAM BAM!!! Rod started knocking at anything above idle!! WTF!!! This is the first time anything like this has happened to me.

So after a long day, night, and morning, I just dropped the block, crank, and rods off at the machine shop. We noticed that the crank was getting starved for oil?? #6 was gone, #5 didnt have much more to go, and so on.

The shortblock was completely blueprinted, RJC girdle, high pressure oil pump, clevite bearings, std/std crank, stock rods, so the problem is a complete surprise....

So my question is, what can I do when I get everything back on Monday to make sure that this doesnt happen again? Has anyone else had an oil starving problem and what was it from? Any help would be greatly appreciated, cause for the first time I am worried about the oiling system on these things!!
 
How did the cam look and did the front cam bearing spin? If your whole crank was starved for oil and you had pressure I'd start there. The only way I'd feel comfortable after something like that is if I figured out what caused the problem. Did you do the assembly?
 
The cam looked 100%. I was expecting it to be flat and the metal from it to have caused the problems, but nope... The front cam bearing was checked during assembly, but I didnt look at it this morning when I disassembled everything. Yes, I did all of the assembly, thats why I confused on this one?? There shouldnt have been any surprises...
 
Who set up all the clearences? They could be off. Also, sound slike something could be blocking oil flow if the entire crank is being starved and initially it was fine.
 
Just an idea: Check out the lifter bores. The bores could be worn and the oil could be hemoraging around the lifter and giving less oil pressure/volume to the rear mains. Or the lifters might be the wrong ones. If the oil band is in the wrong spot, they would unshroud the oil gallery.

Did you enlarge the oil passages to the mains with the high volume pump?

Billy T.
gnxtc2@aol.com
 
Just an idea: Check out the lifter bores. The bores could be worn and the oil could be hemoraging around the lifter and giving less oil pressure/volume to the rear mains. Or the lifters might be the wrong ones. If the oil band is in the wrong spot, they would unshroud the oil gallery.

Did you enlarge the oil passages to the mains with the high volume pump?

Billy T.
gnxtc2@aol.com

Ya, that and check the crank passages. Could be a blockage feeding the rear of the crank.
 
I read about the oiling mods and enlarging the path to the mains when using a HV pump, but how much will that help if the hole in the main bearings, which is much smaller than the stock oil passage, are also not enlarged?
 
.........So after a long day, night, and morning, I just dropped the block, crank, and rods off at the machine shop. We noticed that the crank was getting starved for oil?? #6 was gone, #5 didnt have much more to go, and so on.

......... cause for the first time I am worried about the oiling system on these things!!

A local guy had a similar experience a few years ago. Still have the rod that was "burned" looking like it was starved for oil. After close examination, the shop that did the motor did NOT resize the rod properly. He only had a couple hours run time on the motor.:confused:

With a rod bearing destroyed, oil pressure can be non-exsistant.

The factory rod clearance spec applies to ALL Buick V-6's, and in our opinion and experience, some shops set rod clearance too tight for a turbo motor.

We still have yet to see rod bearing damage on a turbo engine because of too loose rod clearance.:)

There are many 9 sec. stock blocks we have built that have no oiling problems w/o a HV cover, just a modded stock cover and pump, and other internal mods depending on build.
 
.0015 on the rods and .002 on the crank here. No issues and I built it in the garage at home. Plastagauge was how I measured everything. Works for me.
 
Just an idea: Check out the lifter bores. The bores could be worn and the oil could be hemoraging around the lifter and giving less oil pressure/volume to the rear mains. Or the lifters might be the wrong ones. If the oil band is in the wrong spot, they would unshroud the oil gallery.

Did you enlarge the oil passages to the mains with the high volume pump?

Billy T.
gnxtc2@aol.com

That is some scary stuff - makes me wonder about my 300K block...

King? Have you looked at it?
 
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