Just finished a rebuild of Orig 65 283-4bbl. Ran around 200 miles after camshaft breakin and lost power and heard engine noise. Thinking back I think I noticed a loss of Oil Pressure too. A breakdown of the engine last night showed wear in the main and rod bearings progressively worse from back to front, scoring on crank in the first our cylinders from front. This seems to me to be oil pressure loss (lowest pressure at front normally). New Melling pump (which seems to sound OK when you turn shaft), new shaft, HEI dist, new filter etc. The filter canister had been previous replaced with a spin on type adapter. Any clues on diagnosing this one?

Machine work done by one of the local are NASCAR shop back door boys, so I am pretty confident that isn't an issue.

Thanks

What was the clearance on the mains, and was the clearance checked over the entire diameter, or just in one spot?

Take apart the oil pump and see if there was a failure in there.

Dave

Thanks. The fellow that did the machine work had the crank polished & not ground. He has been in the racin businees a long time, but good suggestion to ask.

I spun the shaft and listened to the pump and I could hear what sounded like the gears running, but disassembly is a good idea. On retart after the tow home, had reduced, but some oil pressure. Is is possible there was a restrictio/debris in the oil passages between front and rear? I guess it would be best for me to start with the simple/obvious and work forward.

sounds like a big wad of dirt that was overlooked. Not taking anything away from the NASCAR boys but they don't have to consider the possibility of a wad of hardened sludge in the oil passages. Hot tank won't always get it.

Did you change the oil & filter right after the cam/lifter breakin?

I ask this because what can happen at times is the assmbly lube/grey moly paste can clog the oil filter which will cause significant oil pressure loss/drop when that happens enough so if not caught in time it can damage the motor.

Thats whys its important to change the oil & filter right after cam/lifter breakin is completed.

But if you did in fact change the oil/lifter post cam breakin then its not that . In that case it may be too tight of bottom end clearance related issues or maybe there was some contamination/debries/particulates left in the oil passages & or block in general that scored all the bearings/crank when they got in the oiling system resulting in lower oil pressure & bearing noise/knock.

As a sanity check were any of the main & rod bearing clearances checked durring assembly?

Good luck.

Scott

I'd be looking closely at the filter adapter. Is it the type that retains the original adapter? might want to inspect the oil filter, see if the element is collapsed or anything like that. did you use a HV pump? what kind/weight of oil?

Did the soft plug under the rear main cap bolt get removed/replaced?

Thanks so far to all with input. To further amplify based on questions.
1. Original GM Oil Filter bypass remained.
2. I overestimated mileage on break-in, probably less than 100 miles on engine, so filter had not been changed yet.
3. Original disassembly was real clean (not a gunky engine). Reassembled with assembly lube and Comp Cam break in lube.
4. Have not taken the oil filter apart to look at it. Saw no sludge or buildup of assembly lube on disassembly after failure.
5. Have to check with assembler on HV pump and soft plug under reat main cap bolt.
6. The damage was progressive worse front to back (no scoring in rear, and max scoring at front).

Chk out the oil filter since you didnt change the oil & filter right after the 20-30 min cam/lifter breakin like is std proeceedure and ran it for 100 miles before doing so.

I have seen from time to time where the oil filter can either clog with assemlbly lube-or moly paste,oil filter by pass is stuck and or plugged/or filter simply collapsed due to being partially plugged or due to blocked bypass etc all of which can lower oil pressure enough to cause engine damage which may or may not be the cause of the damage.

Scott

First time I redid my 283 it blew out the center gallery welch plug on the stand when I prelubed it. I just staked it in place for that build, but it's been tapped to 1/4 npt way over 20 years now. Look behind your cam gear, should be 3 plugs,,,,,the 1 in the middle is main gallery, the left and right ones are lifter galleries.