1968 FJ40 - Engine Knocking! - Rod Bearing Mystery?

Investigating rod knock and found mismatched bearings. Trying to piece together what the previous owner did.
We added this '68 FJ40 to our collection in November 2023. Now we're diving in full steam to get it running and on the road!

[@kardyify]

Great research! Well done.

[@RanchoCoyote]

Thank you!

[@cynthiaweintraub3883]

😮

[@ivancollado7946]

Hello Rancho, great video. I have a question. My FJ40 has a loud knocking noise. We checked the bearings, and they are all scratched. My issue is that I do not have the PN/SIZE on the bearings, so I do not know the measurements. What do you think I should do?

[@RanchoCoyote]

Scratches are somewhat normal and might not be the source of your knocking. That said, you should be able to read the bearing PN and over/under size on the backside of the bearing. Did you remove any bearings and look on the back? If yes, and the numbers are gone, you may have to measure the actual thickness of the bearing and compare to known bearings, taking wear into account. However, you will also need to measure the crank pins to see if your crank is damaged or has been ground down to an undersize. Once you have both dimensions, you can tell if there is enough wear to cause a knock. If all your bearings look the same and none of the bearings or crank pins have serious damage from spinning, etc, I'd suspect the knock is from something else. There are lots of videos on youtube that compare knocks from different sources you can listen to and compare to your knock. Let me know if this helps, or is TMI, or you have other questions. Good luck, and thanks for watching!

[@ivancollado7946]

@@RanchoCoyote Thank you for the quick response. This is very useful information, but I am a bit overwhelmed because I don't have the proper tools. I am looking for a machine shop that might be able to handle this. Questions: what are the size options? My mechanic told me to order a few different sizes and go through the process of elimination.

[@RanchoCoyote]

What year is your rig? Have you done a serial number check to confirm the year of your engine? Unless you know for sure, you should check the engine model and year right away. Rod bearings are usually available in .010, .020, .030, and some .040" undersize. "Undersize" refers to the reduced diameter of the rod journal (crank pin) after grinding it down. The bearings themselves are oversize due to the extra thickness to fill in for the smaller (ground down) diameter crank pin. Rock Auto has some good prices on bearings, but I can't vouch for the quality. If you're experimenting, you might be price conscious. SOR is also a reliable source for bearings, and they have an engine SN/Year chart that can help you determine what engine you have. I could also help with that if you need help.

[@ivancollado7946]

@@RanchoCoyote It's a 1972. I am going to order the .010, 020, and 030. I hope one of those will fit and take care of the knocking. Thank you for taking the time to answer my questions. Your assistance is much appreciated!

[@bbaker8078]

When was the last time you adjusted the valves? You could just have a knock from that. I’d start there (easy) before taking the pan off / buying parts unless you know the sound is from the block.