How to Minimize or Eliminate the chance of Rod Knock
--------------------------------------------------------------------------------
Well I hear many people talk of Getting rod knock after doing a engine rebuild. After doing a successfull rebuild, and then gettting knock I was a little worried. Well my knock was caused by a faulty oil pump drive shaft that caused a lack of oil.
It always seems to have a reason, but no one ever looks to themselves as the problem. Don't forget it all comes down to lubrication, machining, and poor assembleing. The bearings ride on a tiny film of oil. running rich, can cause poor lubricating problems. The gas runs past the rings and in to the oil making kerosene, this kills the bearings. Oil that is too hot can also cause bearing fatigue, and failure. Also running to thin of a viscosity, and poor filtering can contribute to bearing failure. Collectively the last problems mentioned can give a proper rebuild a knock. Let's look at what I see as things that can cause rod knock.
1. Faulty oiling system lack of oil, low oil pressure, not enough oil
2. Improper Machine work. i.e. poor tolerances Many machinist don't recognize that the specs must be very precise or there wll be failure
3. All components must be inspected for clearances, and in my opinion don't accept anything that is just within tolerance when it comes to rods.
4. crank must be cut and properly sized by a very reputable machinist. Ask questions you know the answers to. See if his answers match up to what must be done.
5. get good bearings. Clevites are fine but they are reboxed and are farmed out to other bearing companies. My mains were made by global, and my rod bearings made by NDC. They came in a clevite77 box. Call them and ask them if you dont believe me. They don't always use the same companies I hear. I also am told that the ndc bearings are .001 of an inch unersized. I hear that ACL are great and is moslty used in the MKIV's along side of clevite77's. This is your choice choose wisely!
6. Get new rods, or get them cut and resized no matter what! New they ar 36.00 cut they are 15.00 per rod. Arps cost 40.00 and are an option for added insurance.
7. use boots or tape to keep rod bolts from damageing crank!
8. use moly asembly lube that the machinist will give for free. Mine does.
9. DON'T mix end caps, and rods! this will cause knock! some of you don't know this, and after hearing "It knocked after starting" this is my guess a good reason why it knocked. Then you blame the car for your error.
10. after rods areinstalled in the block use a good torque wrench and torque to spec of factory or arp spec reccomendations,and use plastigauge to check clearance
11. Never put in an old oil pump unless you want to do this again!
12. get new oil filter adapter, or go relocation kit and inline thermostat and cooler. The old adpter has a relief valve, and spring which wears over the years. After 150-200k it must be replaced, or you do this again because of low oil pressure. After installing my kit my pressure rose 12psi.
13. Properly tune the engine especially when upping fuel pressure, and adding bigger turbos!
14. Keep oil levels filled as mentioned by Drjonzes, add an extra quart!
15. However; One point is missing that you need to know. The bearings will be different sizes if the crank isn't cut to one size say like .25mm called 10 under. This presents the problem of a newbie, or even a seasoned mechanic mixing up the bearing sizes, and getting rod knock. To avoid this each rod journal must have the proper bearings marked in some form or fashion. You can have him list the sizes for each journal 1-6 in order so you won't have this problem.
When done correctly this procedure will give you a great knock free engine until you run low on oil.
If I have left anything out be sure to chime in.
Anthony
--------------------------------------------------------------------------------
Well I hear many people talk of Getting rod knock after doing a engine rebuild. After doing a successfull rebuild, and then gettting knock I was a little worried. Well my knock was caused by a faulty oil pump drive shaft that caused a lack of oil.
It always seems to have a reason, but no one ever looks to themselves as the problem. Don't forget it all comes down to lubrication, machining, and poor assembleing. The bearings ride on a tiny film of oil. running rich, can cause poor lubricating problems. The gas runs past the rings and in to the oil making kerosene, this kills the bearings. Oil that is too hot can also cause bearing fatigue, and failure. Also running to thin of a viscosity, and poor filtering can contribute to bearing failure. Collectively the last problems mentioned can give a proper rebuild a knock. Let's look at what I see as things that can cause rod knock.
1. Faulty oiling system lack of oil, low oil pressure, not enough oil
2. Improper Machine work. i.e. poor tolerances Many machinist don't recognize that the specs must be very precise or there wll be failure
3. All components must be inspected for clearances, and in my opinion don't accept anything that is just within tolerance when it comes to rods.
4. crank must be cut and properly sized by a very reputable machinist. Ask questions you know the answers to. See if his answers match up to what must be done.
5. get good bearings. Clevites are fine but they are reboxed and are farmed out to other bearing companies. My mains were made by global, and my rod bearings made by NDC. They came in a clevite77 box. Call them and ask them if you dont believe me. They don't always use the same companies I hear. I also am told that the ndc bearings are .001 of an inch unersized. I hear that ACL are great and is moslty used in the MKIV's along side of clevite77's. This is your choice choose wisely!
6. Get new rods, or get them cut and resized no matter what! New they ar 36.00 cut they are 15.00 per rod. Arps cost 40.00 and are an option for added insurance.
7. use boots or tape to keep rod bolts from damageing crank!
8. use moly asembly lube that the machinist will give for free. Mine does.
9. DON'T mix end caps, and rods! this will cause knock! some of you don't know this, and after hearing "It knocked after starting" this is my guess a good reason why it knocked. Then you blame the car for your error.
10. after rods areinstalled in the block use a good torque wrench and torque to spec of factory or arp spec reccomendations,and use plastigauge to check clearance
11. Never put in an old oil pump unless you want to do this again!
12. get new oil filter adapter, or go relocation kit and inline thermostat and cooler. The old adpter has a relief valve, and spring which wears over the years. After 150-200k it must be replaced, or you do this again because of low oil pressure. After installing my kit my pressure rose 12psi.
13. Properly tune the engine especially when upping fuel pressure, and adding bigger turbos!
14. Keep oil levels filled as mentioned by Drjonzes, add an extra quart!
15. However; One point is missing that you need to know. The bearings will be different sizes if the crank isn't cut to one size say like .25mm called 10 under. This presents the problem of a newbie, or even a seasoned mechanic mixing up the bearing sizes, and getting rod knock. To avoid this each rod journal must have the proper bearings marked in some form or fashion. You can have him list the sizes for each journal 1-6 in order so you won't have this problem.
When done correctly this procedure will give you a great knock free engine until you run low on oil.
If I have left anything out be sure to chime in.
Anthony
Last edited:
