For my first car i bought 383 Iroc-big mistake. After finding out that the pistons were put in the wrong hole(backwards valve reliefs on 6 pistons) i wanted it to be right so i could run a bigger cam. So i had it rebuilt-bored .040 over, new pistons, same h-beam rods, bigger stick. Every thing was balanced perfectly, rods resized, block cleaned up, all oil clearances checked twice by 2 different people. The first time it ran it would knock only when it was warmed up, but afterwards when it cooled down it wouldnt, only when it was warm. Tore it back down and found that #8 rod bearing looked as though the bearing was starved for oil, so after rechecking all oil clearences twice again and the whole 9 yards put it all back togeather and darned if it didnt do the same exact thing, cut the oil filter and found bearing material just like before. The only thing i can think of is one of the oil holes is stopped up, starving the bearing for oil, anyone have any ideas? sorry about the mile long thread

 

The rod bearings feed form the mains. You should be able to take a pipe cleaner and push it form the main to the rod journal on the crank. Make sure the rod cap is installed correctly . You could pressurize the engine on a stand and see if you have oil to all rod, main and cam bearings.Usually # 8 is the first to receive oil. Look for missing oil galley plugs and cracks in the min webs.

 

thanx for the reply, we did clean all the oil holes in the crank(srayed w/brake cleaner and blew out w/ a air compressor. What is pressuizing the engine? i dont know much at all about engines, but i have never heard about that, and also we did install the rod caps correctly

 

I think what he's talking about is priming the oiling system on the stand. If so, then you take a distributer with the gear taken off and modified to attach to your drill. Put it into the distributer hole, mesh it with the oil pump driveshaft and spin it, causing it to pump oil to all the places it should be pumping. Then you can check to makes sure oil is going where it should be and not leaking out somewhere it shouldn't.

 

Sounds like that rod is too tight or you need to clean out your block better.

 

To do a leak test you need a pressure container that you can attach to the oil galley . Full the tank with about 10 psi of air and and 2 quarts of clean motor oil, allow the oil to circulate . the cam lifters and distributor all have to be in place. If you see excessive leakage you've found the problem. I agree a tight rod will also cause the problem but if they were all checked and reconditioned what are the chances of lighting striking twice.

 

i watched the guy torque every single rod. I also had the block bead blasted, and it looked brand new when it was done after being blasted it was all washed. Is possible some of the beads are lodged somewhere?

 

The possibility of some left over media from the blast cabinet is pretty high. Although a thurough cleaning with a preasurized washer USUALLY gets all of the media out of the engine, especially after using air and a chemical spray. Most of the time if your oil passage ways are plugged the damage to the bearings will start with the #1 rod since it is the last to get oil. My question is how was the engine tin (oil pan, valve covers, timing cover, etc.) cleaned?

The shop I used to work at had this same problem with a 2.8 V-6 in an early third-gen Camaro. A new guy used a media blaster to clean all of the tin, and thought he had cleaned all of the beads out. After I disassembled the entire engine I found the same outcome you described. I closely inspected the tin and found a lot of the media beads still tucked inside all of the seams and cracks in the tin. I had to put all of the tin back in the oven to bake off the media, then clean it with a airless cabinet that uses a larger metal bead. Even after the airless, careful cleaning had to be done to ensure no media was left anywhere. We also replaced the oil pump and pickup tube just because we could not ensure there was no media trapped inside. After re-assembly that engine has been running perfectly for the last 4 years, and the kid drives it up and down California all of the time.

Another question is what kind of oil pump and pan are you using? Using a "high volume" oil pump on a stock sized oil pan can actually pump the pan dry. Usually if one wants to use a high volume oil pump they should also include a higher capacity oil pan as well.

 

the valve covers were brand new, but i am pretty sure the oil pan, and timing cover were washed. It does have a high volume oil pump w/stock 5-quart oil pan. Before it was rebuilt it had the high vol. pump w/stock pan and gave no trouble, the old bearings looked good for the amount of miles on them. I dont think the oil pan & timing cover were blasted though. Thanks for the reply

 

when you did your first tear down to check the bearing, did you replace or clean the pickup tube and flush out the pump? how about the end of the connectig rod on the wristpin, some excess play (or too tight) on that end might chew a bearing. Just throwing out my last couple thoughts. Did you check the other bearings as well? what did they look like? How was the block dried after washing? As long as the engine builder was quite liberal with the compressed air on the block there shouldn't be any media left anywhere, but washing alone won't get rid of it all.