Hi! I have a question in general: When I do check my crankshaft bearing clearances (torqueing them down and measuring without a crank in the block) can I re-use those bearings when I finally mount the crank? Or do I have to buy a whole new set of crank and rod bearings? My friend said after toqueing down crank caps and rod caps the bearings get crushed and cannot be re-used. On the internet I found only one reference which said that they only get crushed "elastically", so they would do get back into their origin shape after loosening the caps.... Marlon
When checking crankshaft bearing clearances by torquing down the caps without the crankshaft in place, it’s generally acceptable to reuse the bearings for the final assembly, provided the following conditions are met: 1. Torque Application: Bearings are designed to deform elastically when torqued down, meaning they will return to their original shape once the caps are loosened, as long as proper torque procedures are followed. Over-torquing or repeated torquing can lead to damage, which may affect bearing integrity and clearances. 2. Inspection After Measuring: Before reusing the bearings, carefully inspect them for any signs of damage, deformation, or wear. If you notice scoring, scratches, or signs of uneven pressure, replace them. 3. Number of Torque Cycles: Avoid excessive torque cycles. Bearings can tolerate a few cycles during assembly and measurement, but repeated clamping can increase the risk of fatigue or damage. 4. Cleanliness is Critical: Ensure everything is perfectly clean during the measuring process. Any debris between the bearings and caps can cause uneven deformation and compromise the bearing surface. Your Friend’s Concern: The idea that bearings are “crushed” and cannot be reused after torquing is a misunderstanding. Bearings are designed to handle these elastic deformations as part of the assembly process. However, if over-torqued or misaligned, they can suffer permanent damage. Proper care and correct torque specifications ensure reusability. Recommendation: If you followed the correct procedures and ensured cleanliness during your clearance checks, you can safely reuse the bearings. However, if there’s any doubt about their condition or if you’ve torqued them down multiple times, it’s safer to replace them to avoid potential engine failure later. Bearings are relatively inexpensive compared to the potential cost of damage.
@@vac-motorsports Thank you so much for your detailed answer. Thank you for taking your time to answer my question while explaining all aspects. Thank you! Marlon
I'm not sure about the BMW platform but I know one thing bearings are not perfectly round like your main bearing journals. This is by design. The horizontal measurement will always be different than the vertical. This is due that went under high horsepower. The crankshaft is trying to be pushed out of the block and the bearings bearings are made to maintain clearance for oil
It is said that some BMW engines have much too tight rod bearing clearance. I called VAC about possibly having BE bearings installed, also coated, but designed to have a little bit more clearance. So that the engine oil can better lubricate the bearings. Paul Milano was quoted to have joked, "Why would you want to install worn bearings?" Would love to hear more about this issue ...
@@tonysalloum6973 Thanks, Tony. Why do some people recommend rod bearings that provide a little more clearance, whereas you guys do not recommend those?
That's not true. The VAC Bearings do have more clearance than OE bearings. Others claim that they don't have enough clearance but as I mention in the video, the clearance has a range and is different for different builders. If you can't measure the crank journal, the big end of the rod after it is torqued properly, and can't measure the bearing accurately down to 0.0001"-0.0002" then how do you really know what you're true clearance is. But again, the VAC Rod Bearings do have additional clearance. 😊
@@tonysalloum6973 In the video, it looks like you're building an engine for FI, replacing the crankshaft and the connecting rods, and while it's all apart doing all of the relevant measurements of the shaft and rods and bearings. If you're just inspecting and possibly replacing bearings on a stock engine from underneath the car, I presume you can't do all of these measurements. So, if you recommend replacing the rod bearings, how do you choose the right thickness for the bearings?
Haha!!! That does like that. 😊 Yes, it's absolutely correct. You can't measure rods accurately in the engine. The VAC bearings are based on the OE bearing dimension but with the required additional clearance, based on many years of experience, to keep you in a safe range.
but would not be better than to have an electric pump prime the oil pressure before starting the engine, and keeping the oil pressure up when you shut the engine till the crank stops ?
Hi! I have a question in general: When I do check my crankshaft bearing clearances (torqueing them down and measuring without a crank in the block) can I re-use those bearings when I finally mount the crank? Or do I have to buy a whole new set of crank and rod bearings? My friend said after toqueing down crank caps and rod caps the bearings get crushed and cannot be re-used. On the internet I found only one reference which said that they only get crushed "elastically", so they would do get back into their origin shape after loosening the caps.... Marlon
When checking crankshaft bearing clearances by torquing down the caps without the crankshaft in place, it’s generally acceptable to reuse the bearings for the final assembly, provided the following conditions are met:
1. Torque Application: Bearings are designed to deform elastically when torqued down, meaning they will return to their original shape once the caps are loosened, as long as proper torque procedures are followed. Over-torquing or repeated torquing can lead to damage, which may affect bearing integrity and clearances.
2. Inspection After Measuring: Before reusing the bearings, carefully inspect them for any signs of damage, deformation, or wear. If you notice scoring, scratches, or signs of uneven pressure, replace them.
3. Number of Torque Cycles: Avoid excessive torque cycles. Bearings can tolerate a few cycles during assembly and measurement, but repeated clamping can increase the risk of fatigue or damage.
4. Cleanliness is Critical: Ensure everything is perfectly clean during the measuring process. Any debris between the bearings and caps can cause uneven deformation and compromise the bearing surface.
Your Friend’s Concern:
The idea that bearings are “crushed” and cannot be reused after torquing is a misunderstanding. Bearings are designed to handle these elastic deformations as part of the assembly process. However, if over-torqued or misaligned, they can suffer permanent damage. Proper care and correct torque specifications ensure reusability.
Recommendation:
If you followed the correct procedures and ensured cleanliness during your clearance checks, you can safely reuse the bearings. However, if there’s any doubt about their condition or if you’ve torqued them down multiple times, it’s safer to replace them to avoid potential engine failure later. Bearings are relatively inexpensive compared to the potential cost of damage.
@@vac-motorsports Thank you so much for your detailed answer. Thank you for taking your time to answer my question while explaining all aspects. Thank you! Marlon
TEŞEKKÜRLER
I'm not sure about the BMW platform but I know one thing bearings are not perfectly round like your main bearing journals. This is by design. The horizontal measurement will always be different than the vertical. This is due that went under high horsepower. The crankshaft is trying to be pushed out of the block and the bearings bearings are made to maintain clearance for oil
It is said that some BMW engines have much too tight rod bearing clearance. I called VAC about possibly having BE bearings installed, also coated, but designed to have a little bit more clearance. So that the engine oil can better lubricate the bearings. Paul Milano was quoted to have joked, "Why would you want to install worn bearings?" Would love to hear more about this issue ...
Hi. What would you like clarified? I'm not understanding exactly what you are asking.
@@tonysalloum6973 Thanks, Tony. Why do some people recommend rod bearings that provide a little more clearance, whereas you guys do not recommend those?
That's not true. The VAC Bearings do have more clearance than OE bearings. Others claim that they don't have enough clearance but as I mention in the video, the clearance has a range and is different for different builders. If you can't measure the crank journal, the big end of the rod after it is torqued properly, and can't measure the bearing accurately down to 0.0001"-0.0002" then how do you really know what you're true clearance is. But again, the VAC Rod Bearings do have additional clearance. 😊
@@tonysalloum6973 In the video, it looks like you're building an engine for FI, replacing the crankshaft and the connecting rods, and while it's all apart doing all of the relevant measurements of the shaft and rods and bearings. If you're just inspecting and possibly replacing bearings on a stock engine from underneath the car, I presume you can't do all of these measurements. So, if you recommend replacing the rod bearings, how do you choose the right thickness for the bearings?
Haha!!! That does like that. 😊
Yes, it's absolutely correct. You can't measure rods accurately in the engine. The VAC bearings are based on the OE bearing dimension but with the required additional clearance, based on many years of experience, to keep you in a safe range.
but would not be better than to have an electric pump prime the oil pressure before starting the engine, and keeping the oil pressure up when you shut the engine till the crank stops ?