The Stovebolt Site Forums The Shop Area Engine Shop that rattling 235

A while back I posted about my 235 rattling just before shift points. Everyone said it was rod bearings most likely and check it soon. I also stated they were new and less than 200 miles in service. Question is, when I take oil pan off,is there a way to find which bearing is the worst or if some are good and others bad? I probably don't have to tell you I'm not a mechanic. I can do most everything to this truck but when it gets inside the engine I'm looking for help.

A quick way to find which is the loosest is to grab the rod by hand and see if you can get any up and down movement. The best way to check for proper clearance is to go to an automotive supply house and buy some red plastic guage. Use as directed and it will give you an indication of how much bearing clearance you have. You can use this for rods and mains. Don't forget to check the crankshaft thrust bearing. The way to check this is to use a screwdriver or small prybar and pry the crankshaft forward and then rearward, there should only be about .004 to .006 end play.

Have you had anyone familar with engines listen to your engine or drive the truck before you pull the pan? There is a lot of good mechanics on this site,especially Racecarldad who actually worked on these things for a living, but its very difficult to trouble shoot noises over the computer.

Rev the engine until it starts to rattle. Remove the spark plug wire from the plug one cylinder at a time, running on five cylinders. If the rattling continues, re-connect the wire & remove the wire from another cylinder. If the rattling stops or isn't as loud, you found the location .

Thanks again for the great info! I think IO found the two that were causing the most problem. Number two and four were the culprits. Please see my new post on oversize rod bearings. I could sure use the info..

Pull the pan,if you can snap a rod forward or back easily it's probably within 3 to 5 thousands and servicable, if you cant, its too darn tight.Another way to check is the all purpose brick on the gas pedal, about 5 grand should do it on a 235, hide the wife and kids, run like hell, like away from the truck, and listen for interesting noises, the bad rods are the ones flying over your head and impacting into your neighbors roof, garage,dog house, etc.

Pull the pan,if you can snap a rod forward or back easily it's probably within 3 to 5 thousands and servicable, if you cant, its too darn tight.Another way to check is the all purpose brick on the gas pedal, about 5 grand should do it on a 235, hide the wife and kids, run like hell, like away from the truck, and listen for interesting noises, the bad rods are the ones flying over your head and impacting into your neighbors roof, garage,dog house, etc.

Somebody will probably comment here but if you have been hearing a knock, there will be damage to the crankshaft. I think you might find some metal transferred to the crankshaft at a minimum.

I had a rattle as described and got the advice to rev the engine and then pull the plug wires, just as i got out the door it threw a rod. the rebuild had not included putting lock nuts on the bearing bolts. Just saying.