I had two rod bearing failures on the same motor same #5 journal. Just wondering the leading causes on our mod motors. Its a 03 iron block diamond pistons cobra crank Olliver rods. First time had about 30 runs second time 5 runs only with brand new crank rods checked and balanced at Olliver and new bearings. I think the bore may be out of align.

 

what was the bearing clearence ? what oil pump ?

 

I would really like to know what oil was in it ..

 

Also a rare issue but an egg shaped rod from bad cast or stretched. Takes a good micrometer to check.

 

First one was already together built by victory racing engines in Michigan. Second one was put together by a friend who always helps me out very particular never had a problem before. Why the same rod though if it was assembly? Other journals were perfect except #1 because its on the same throw.

 

Only had plasti gauge all between 1.5 and 2. Brand new melling billet pump.

 

Royal purple. 5/30

 

It was the same rod but I sent them back to the maker to have them checked and balanced and cost me over 300 bucks but you never know.

 

pics.?

What kind of machine work was done to the block.?
was it clean after it was machine.?
how about the crank.?

more info , please

 

Got a pict of the bearings? Im with Mod Mustang Racing on this one.

Dumb question but did you check the oil passage in the crank that feeds that journal? Did you pull the crank? If not did you check the main bearings?
not sure on mod motors but i helped a local guy on a sbc that kept eating rod bearings quite quickly only making 5-20 runs and having to replace the bearings over and over, (engine shop replaced the rod bearings once and told him the second time it was something he was doing) I tore the motor down for him all the way, and found out quickly if the cap bearing is in the block no oil can get through..... lmao. Crank, block (from mains finally seizing to crank and spinning) and rods were scrap. They probably would have found it if they pulled all the main caps instead of the one furthest from the oil pump (assuming if it was oil starvation that bearing would show more damage then all the others)

 

Not sure about the first time but everything was cleaned the second time and nothing was done to the block besides a quick hone. Crank was a brand new Kellogg no machining done the second time just cleaned.

 

Very odd indeed.

 

Oil problem .. jmo

 

Could it be something with the block only affecting #5?

 

Most likely improper cleaning of everything after a bearing failure. We will removed every oil gallery plug from the block and cylinder heads and thoroughly clean every component that is being reused. You would be surprised the amount of metal that can get stuck in the heads, and it will eventually make its way back into the pan, though the pump and back to your brand new bearings. I've seen it happen way too many times. Pull out a couple of the gallery plugs in the heads and I bet there will be metallic material there. I highly doubt there was a problem with the rod. We use Oliver's most of our modular engines and they are always with .0001" of each other.