I'm currently going through a sorta DIY engine rebuild in another thread here:
http://www.nsxprime.com/forum/showthread.php/154927-Semi-DIY-Mild-Engine-Build-for-FI/page19
I'd like to find out who else has had problems with their recent engine rebuilds, and spinning OEM-replacement rod or main engine bearings?
NA1MT has posted he spun main bearings on a fresh LOVEFAB rebuild here "due to lost oil pressure for a split second":
http://www.nsxprime.com/forum/showthread.php/162084-Cody-and-LoveFab?p=1703504&viewfull=1#post1703504
This seems a little strange to momentarily loose oil pressure in a controlled environment. I'm curious if there's more info on whether or not it was on a dyno or the street, if the main bearings were new OEM Honda's, or what....
I've heard that there was a recent rebuild done by a very reputable shop on the West Coast that just spun rod bearings too. Maybe they'll be able to post the particulars about what components were used in that build.
Dimer recently spun rod bearings on his too, just 125 miles after his rebuild:
http://www.nsxprime.com/forum/showthread.php/159361-ASM-Time-Attack-CTSC-NSX/page6?p=1729819&viewfull=1#post1729819
This was with OEM rods, OEM rod bolts, and I assume new OEM Honda bearings. It's similar to my situation....
For me, I'm doing a simple refresh. Reusing OEM crank, rods, main caps, and was just buying replacement OEM rod and main bearings to match the colors on the old bearings I had removed. The old main bearings looked a little worn, but the old rod bearings were in great shape. The color codes on the bearings I took out matched the deciphered Service Manual from the stampings in the block and crank hieroglyphics. So I thought I was good to go just ordering new matching bearings from Honda....
Well, the crank main bearings had no troubles during installation and checking them with Plastigage. Plastigage was uniformly squished, and all measurements came back right in the idle of Honda clearance specs. After assembly lube, and final torque, crankshaft turned smooth and the "stiction" torque to overcome the static coefficient of friction with just the crank mains in place was less than 1 ft-lb. Pretty good.
Then came the rods bearings. I re-used the OEM rod bolts (like Dimer) since they looked great, didn't show any signs of necking and yielding, I wasn't adding rotating mass or increasing the engine speed, and the Service Manual says you can reuse them. With new OEM rod bearings the exact same color as the ones I removed, only three of the rod bearings had clearance in the wide range Honda specifies (0.0016 to 0.0024"). Two were ~0.0009", and the last one was ~0.0030". WTF? The crank journals were just micropolished - no machining on them. I tried to refine my method for Plastigaging by locking the crank and inserting fine feeler gages between the rod cap sides and the crankshaft in order to ensure the crank and rods weren't moving while I was torqueing and un-torqueing the rod nuts. After multiple measurements, I realized the clearances were definitely off. For each piston and rod I inserted, after the Plastigage check and then cleaning off and adding final assembly lube, I put my torque wrench on the crank and measured the breakaway torque due to the new piston rings and rod bearings/wrist pin friction.
I went ahead and cleaned off the plastigage on the two tight rods, lubed them, and installed each one in the engine again. Each of these added significant crankshaft rotational resistance that indicated, yes, they were too tight. So I removed them, checked online to see if I could get within clearance spec by buying different-sized OEM Honda bearings, and then made another Honda order.
So, for the two tight rods that originally had green/brown color combos, I bought all red bearings that should make them close to the small clearance side of the spec:
Rod bearing thickness by color
Blue ....0.0594”- 0.0593”
Black ...0.0593”- 0.0592”
Brown .0.0592”- 0.0591”
Green ..0.0591”- 0.0590”
Yellow .0.0590”- 0.0589”
Pink ....0.0589”- 0.0587”
Red .....0.0587”- 0.0586”
I also bought two blues and two blacks to try and tighten up the clearance on the one loose rod. Sat back and waited 1.5 weeks for the new OEM bearings to arrive from Honda. All of these bearings in my build came from reputable Honda dealers - they weren't off Ebay. The bearings I took out were all Taiho bearings. From internet searches, Taiho and Daido are interchangeable bearing manufacturers Honda uses.
New Taiho bearings arrived, so I go out and install them. Basically, same clearances as before, and the tight clearances still add significant resistance to turning the crank. Not that I can't turn the crank and would have been scratching the crap out of the bearings, but since I kept a log of additional torque to overcome each rod/piston addition, I knew it just wasn't consistent.
Removed everything again. Just for fun, I dug out an old set of green/brown rod bearings that I had removed (with 130k miles on them), and installed them in the rod that had 0.0030" clearance with the thickest blue/blue bearings you can buy from Honda. Checked the clearance with Plastigage the way I've always checked it.... Freakin clearance is right at 0.0016"
So that's where I am now.
Bearings are complicated. They are designed with a certain amount of crush, spread, and eccentricity to account for accurate fitup and operation in the rod big end. You can't see any variation in old or new bearing measurements with your eyes. But here's what I did notice:
* Old bearings and new bearings are all Taihos: http://www.taihonet.co.jp/e/index0.html
* New bearings had an inconsistent bearing surface color. I'm not exactly sure of the bearing composition that Honda specifies, but I assume it is a Al-Sn-Si alloy that Taiho advertises on their website. Some of the bearings were dull and "oxidized" in the package, where others were shinier. After checking each new bearing, I washed them with soap and water, dried them, and then wiped with brake cleaner. Surfaces as installed all looked about the same after I did that.
* I don't have the correct ball micrometer to accurately measure bearing thicknesses, but I don't get consistent readings at all comparing old and new bearings thickness measurements with just my calipers. My micrometer edges would dig into the bearings if I tried. Bearing thicknesses are definitely inconsistent though, and I'm not talking about due to wear. Even new-new bearings are not reading consistently. This is proven by my test with the old bearings on the one rod.
* I used my cheapy dial bore indicator and micrometer to measure and calculate the real clearance with what I was observing with Plastigage. Taking into account the accuracy of my tools and my limited machinist abilities, the Plastigage and measurements were close to each other.
Bottom line is this: After two weeks, 23 brand-new OEM Honda bearings purchased from Honda dealers (I bought extras just in case and each bearing has a tolerance to it anyways), about 1.5ft of green Plastigage used, I am still messing with rod bearings to get the right clearance. If I were building an old Chevy engine, rod bearing tolerances are OK if you are between 0.001 to 0.003". I want to be around 0.002" rod bearing clearance - right in the middle of the clearances that Honda specifies.
Problems with too tight of clearance:
-Increased oil temperature.
-Run the risk of not being able to maintain an oil film.
Problems with too big of a clearance:
-Increase the flow of oil through that clearance and away from other vital areas of the engine.
-May not be able to sustain the correct hydrodynamic oil wedge in that clearance.
So, an engine can be built on the "tight" side if the oil is correctly specified and you have sufficient oil cooling. An engine can be built on the "loose" side if the oil is correctly specified and you have sufficient volume/pressure from the oil pump. One of the worst things for either engine is to have a combination of tight and loose clearances though.
I suspect there is an issue with new OEM Honda bearings. Can anyone else that has had recent issues with their engine bearings please post and explain the particulars of your issues? OEM crank, OEM rods, OEM bearings, etc?
Thanks,
Dave
- - - Updated - - -
So, for me, I've bought new ARP rod bolts and will go ahead and send everything to a machinist. They'll press out the old rod bolts, press in the new ones, and then check the rod big end to make sure it is perfectly round. I'll also take them the crank, so they can measure the journal diameters, and match them up with the right rod inner diameters to calculate the bearing thicknesses I'll need.
I'll probably go ahead and take my new OEM bearing supply and see if they can measure those too without screwing them up. I'd like to use my OEM supply since I've spent about $300 on them. If not, I'll buy ACL bearings since they are nominally a "green" Honda bearing thickness and should be what I need. Hopefully their QC is better than these crappy Taiho rod bearings.
ARP rod bolts are here Monday. Only $150 shipped from Florida. I'm going to check out a machine shop Monday that is about 45 minutes away from me....
Dave
http://www.nsxprime.com/forum/showthread.php/154927-Semi-DIY-Mild-Engine-Build-for-FI/page19
I'd like to find out who else has had problems with their recent engine rebuilds, and spinning OEM-replacement rod or main engine bearings?
NA1MT has posted he spun main bearings on a fresh LOVEFAB rebuild here "due to lost oil pressure for a split second":
http://www.nsxprime.com/forum/showthread.php/162084-Cody-and-LoveFab?p=1703504&viewfull=1#post1703504
This seems a little strange to momentarily loose oil pressure in a controlled environment. I'm curious if there's more info on whether or not it was on a dyno or the street, if the main bearings were new OEM Honda's, or what....
I've heard that there was a recent rebuild done by a very reputable shop on the West Coast that just spun rod bearings too. Maybe they'll be able to post the particulars about what components were used in that build.
Dimer recently spun rod bearings on his too, just 125 miles after his rebuild:
http://www.nsxprime.com/forum/showthread.php/159361-ASM-Time-Attack-CTSC-NSX/page6?p=1729819&viewfull=1#post1729819
This was with OEM rods, OEM rod bolts, and I assume new OEM Honda bearings. It's similar to my situation....
For me, I'm doing a simple refresh. Reusing OEM crank, rods, main caps, and was just buying replacement OEM rod and main bearings to match the colors on the old bearings I had removed. The old main bearings looked a little worn, but the old rod bearings were in great shape. The color codes on the bearings I took out matched the deciphered Service Manual from the stampings in the block and crank hieroglyphics. So I thought I was good to go just ordering new matching bearings from Honda....
Well, the crank main bearings had no troubles during installation and checking them with Plastigage. Plastigage was uniformly squished, and all measurements came back right in the idle of Honda clearance specs. After assembly lube, and final torque, crankshaft turned smooth and the "stiction" torque to overcome the static coefficient of friction with just the crank mains in place was less than 1 ft-lb. Pretty good.
Then came the rods bearings. I re-used the OEM rod bolts (like Dimer) since they looked great, didn't show any signs of necking and yielding, I wasn't adding rotating mass or increasing the engine speed, and the Service Manual says you can reuse them. With new OEM rod bearings the exact same color as the ones I removed, only three of the rod bearings had clearance in the wide range Honda specifies (0.0016 to 0.0024"). Two were ~0.0009", and the last one was ~0.0030". WTF? The crank journals were just micropolished - no machining on them. I tried to refine my method for Plastigaging by locking the crank and inserting fine feeler gages between the rod cap sides and the crankshaft in order to ensure the crank and rods weren't moving while I was torqueing and un-torqueing the rod nuts. After multiple measurements, I realized the clearances were definitely off. For each piston and rod I inserted, after the Plastigage check and then cleaning off and adding final assembly lube, I put my torque wrench on the crank and measured the breakaway torque due to the new piston rings and rod bearings/wrist pin friction.
I went ahead and cleaned off the plastigage on the two tight rods, lubed them, and installed each one in the engine again. Each of these added significant crankshaft rotational resistance that indicated, yes, they were too tight. So I removed them, checked online to see if I could get within clearance spec by buying different-sized OEM Honda bearings, and then made another Honda order.
So, for the two tight rods that originally had green/brown color combos, I bought all red bearings that should make them close to the small clearance side of the spec:
Rod bearing thickness by color
Blue ....0.0594”- 0.0593”
Black ...0.0593”- 0.0592”
Brown .0.0592”- 0.0591”
Green ..0.0591”- 0.0590”
Yellow .0.0590”- 0.0589”
Pink ....0.0589”- 0.0587”
Red .....0.0587”- 0.0586”
I also bought two blues and two blacks to try and tighten up the clearance on the one loose rod. Sat back and waited 1.5 weeks for the new OEM bearings to arrive from Honda. All of these bearings in my build came from reputable Honda dealers - they weren't off Ebay. The bearings I took out were all Taiho bearings. From internet searches, Taiho and Daido are interchangeable bearing manufacturers Honda uses.
New Taiho bearings arrived, so I go out and install them. Basically, same clearances as before, and the tight clearances still add significant resistance to turning the crank. Not that I can't turn the crank and would have been scratching the crap out of the bearings, but since I kept a log of additional torque to overcome each rod/piston addition, I knew it just wasn't consistent.
Removed everything again. Just for fun, I dug out an old set of green/brown rod bearings that I had removed (with 130k miles on them), and installed them in the rod that had 0.0030" clearance with the thickest blue/blue bearings you can buy from Honda. Checked the clearance with Plastigage the way I've always checked it.... Freakin clearance is right at 0.0016"
So that's where I am now.
Bearings are complicated. They are designed with a certain amount of crush, spread, and eccentricity to account for accurate fitup and operation in the rod big end. You can't see any variation in old or new bearing measurements with your eyes. But here's what I did notice:
* Old bearings and new bearings are all Taihos: http://www.taihonet.co.jp/e/index0.html
* New bearings had an inconsistent bearing surface color. I'm not exactly sure of the bearing composition that Honda specifies, but I assume it is a Al-Sn-Si alloy that Taiho advertises on their website. Some of the bearings were dull and "oxidized" in the package, where others were shinier. After checking each new bearing, I washed them with soap and water, dried them, and then wiped with brake cleaner. Surfaces as installed all looked about the same after I did that.
* I don't have the correct ball micrometer to accurately measure bearing thicknesses, but I don't get consistent readings at all comparing old and new bearings thickness measurements with just my calipers. My micrometer edges would dig into the bearings if I tried. Bearing thicknesses are definitely inconsistent though, and I'm not talking about due to wear. Even new-new bearings are not reading consistently. This is proven by my test with the old bearings on the one rod.
* I used my cheapy dial bore indicator and micrometer to measure and calculate the real clearance with what I was observing with Plastigage. Taking into account the accuracy of my tools and my limited machinist abilities, the Plastigage and measurements were close to each other.
Bottom line is this: After two weeks, 23 brand-new OEM Honda bearings purchased from Honda dealers (I bought extras just in case and each bearing has a tolerance to it anyways), about 1.5ft of green Plastigage used, I am still messing with rod bearings to get the right clearance. If I were building an old Chevy engine, rod bearing tolerances are OK if you are between 0.001 to 0.003". I want to be around 0.002" rod bearing clearance - right in the middle of the clearances that Honda specifies.
Problems with too tight of clearance:
-Increased oil temperature.
-Run the risk of not being able to maintain an oil film.
Problems with too big of a clearance:
-Increase the flow of oil through that clearance and away from other vital areas of the engine.
-May not be able to sustain the correct hydrodynamic oil wedge in that clearance.
So, an engine can be built on the "tight" side if the oil is correctly specified and you have sufficient oil cooling. An engine can be built on the "loose" side if the oil is correctly specified and you have sufficient volume/pressure from the oil pump. One of the worst things for either engine is to have a combination of tight and loose clearances though.
I suspect there is an issue with new OEM Honda bearings. Can anyone else that has had recent issues with their engine bearings please post and explain the particulars of your issues? OEM crank, OEM rods, OEM bearings, etc?
Thanks,
Dave
- - - Updated - - -
So, for me, I've bought new ARP rod bolts and will go ahead and send everything to a machinist. They'll press out the old rod bolts, press in the new ones, and then check the rod big end to make sure it is perfectly round. I'll also take them the crank, so they can measure the journal diameters, and match them up with the right rod inner diameters to calculate the bearing thicknesses I'll need.
I'll probably go ahead and take my new OEM bearing supply and see if they can measure those too without screwing them up. I'd like to use my OEM supply since I've spent about $300 on them. If not, I'll buy ACL bearings since they are nominally a "green" Honda bearing thickness and should be what I need. Hopefully their QC is better than these crappy Taiho rod bearings.
ARP rod bolts are here Monday. Only $150 shipped from Florida. I'm going to check out a machine shop Monday that is about 45 minutes away from me....
Dave
