• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Problem With New OEM Rod and Main Engine Bearings?

Joined
25 April 2005
Messages
3,066
Location
Western PA
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":mad:

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
 
I wish I had something meaningful to add but you sound like you are on top of it...albeit rightfully frustrated!
 
I wish I had something meaningful to add but you sound like you are on top of it...albeit rightfully frustrated!

When I built my f24 stroker I used the plasti gauge method and to be honest I got diff readings everytime :/. Since I was using a oem crank and block not machined or anything I just matched the colors as per the block and crank coding.

the crank should have numbers for each journal and same for the block. You match the codes up and the Honda chart will give you the size. I just used these sizes and pretty much crossed my fingers. Worked great! I put like 25k on the block, sold the bottom end and the owner now out about another 20 on it. Still handling strong!
 
When I built my f24 stroker I used the plasti gauge method and to be honest I got diff readings everytime :/. Since I was using a oem crank and block not machined or anything I just matched the colors as per the block and crank coding.

the crank should have numbers for each journal and same for the block. You match the codes up and the Honda chart will give you the size. I just used these sizes and pretty much crossed my fingers. Worked great! I put like 25k on the block, sold the bottom end and the owner now out about another 20 on it. Still handling strong!

Thanks. I did decipher the markings on the crank and block to get the right bearing sizes. They also matched with the colors I physically took off. Those were the color bearings I ordered and originally put back in the car since the crank journals and rod big ends were not touched in the rebuild.

There is a little bit of art in using Plastigage. I've gone through about 1.5ft of it, and feel pretty comfortable with it now. I look at how I'm measuring with it compared to various pictures of others doing it on the internet, and I can see how they'd get inaccurate readings!

Furthermore, I think my Plastigage readings were correct because:

1) It matched the precision measurements I took with the micrometer and dial bore indicator on one of the rods.
2) The two rods that indicated too tight of clearances really increased the rotational torque when turning the crank over by hand. It was too tight.

Coupled with the recent spun bearings on three other NSX engines, I decided not to just "put it back together." That thought did cross my mind though!

Dave
 
Last edited:
Thanks. I did decipher the markings on the crank and block to get the right bearing sizes. They also matched with the colors I physically took off. Those were the color bearings I ordered and originally put back in the car since the crank journals and rod big ends were not touched in the rebuild.

There is a little bit of art in using Plastigage. I've gone through about 1.5ft of it, and feel pretty comfortable with it now. I look at how I'm measuring with it compared to various pictures of others doing it on the internet, and I can see how they'd get inaccurate readings!

Furthermore, I think my Plastigage readings were correct because:

1) It matched the precision measurements I took with the micrometer and dial bore indicator on one of the rods.
2) The two rods that indicated too tight of clearances really increased the rotational torque when turning the crank over by hand. It was too tight.

Coupled with the recent spun bearings on three other NSX engines, I decided not to just "put it back together." That thought did cross my mind though!

Dave


i understand. Plus an nsx motor is much more money to take that gamble on.
 
I've recently encountered issues with main bearings. Measuring with my ball end mic, I found that between several green, brown, and black bearings the colors had little to no "bearing" (huehuehue) on the relative thickness of the bearings. Some greens were thicker than browns or blacks, some browns thicker than black, etc. QC is a mess right now, be careful y'all.

An interest data point is that Cole Mulvey of Bad Guys Worldwide (Honda machine shop specializing in cylinder heads but also does a lot of B/D/H/F block work) mentioned that Honda uses 2 bearing suppliers, Taiho and Daido. The main bearings available for the NSX are all Taiho, which are the cheapo bearings usually found in economy engines, and Daido did the bearings for the performance 4 cylinder engines.

Weirder still, The C30 uses only Taiho rod bearings, while the C32 switched to Daido rod bearings.
 
Last edited:
Yeah, in my first post above, all of my old and new main and rod bearings were noted as being Taiho. I didn't have the proper ball micrometer to confirm the inconsistent thicknesses, so thanks for confirming my suspicion.

I got lucky on the replacement OEM main bearings being a good set. My frustration with rod bearings (I have a small fortune in unusable crappy OEM Honda rod bearings now) lead me to going with an aftermarket rod bearing manufacturer to fit my OEM Ti rods.
 
Yeah, in my first post above, all of my old and new main and rod bearings were noted as being Taiho. I didn't have the proper ball micrometer to confirm the inconsistent thicknesses, so thanks for confirming my suspicion.

I got lucky on the replacement OEM main bearings being a good set. My frustration with rod bearings (I have a small fortune in unusable crappy OEM Honda rod bearings now) lead me to going with an aftermarket rod bearing manufacturer to fit my OEM Ti rods.
Who did you go with for rod bearings? I’m looking to get some and it seems like OEM are pretty inconsistent
 
Man, this was ten years ago, but I ended up with custom King bearings. They worked with me as I developed my own turbo setup that ended up with 350 ft-lbs of torque at just 2500 RPM. I needed bearings to support the increased load and IIRC, we modified their B-series tri-metal bearings. I do remember they were black, so it had their polymer coating. Also, I had to go to an aftermarket dry-sump pump to get the flow/pressure needed at that low of engine rpm to support the load.

Check ACL and I vaguely remember some of the old Nissan rod bearings may be interchangeable. Or maybe QC has improved and you get good OEM ones this time.
 
Nissan VG30 rod bearings should fit but the tangs are in the wrong place and would need to be cut off if you were buying them off the shelf and you'd need to drill an oil hole if you were using OEM rods and wanted to keep the extra cylinder lubrication. For what its worth, most aftermarket rods don't have this hole and when I called and asked Carrillo they said they didn't think it was needed with forged pistons. You should be able to get clearances within spec by mixing STD, +0.001, and -0.001 shells.

The rod bearings I've ordered more recently have been fine though, and with a ball end mic you can verify thicknesses. WPC treated OEM bearings are what I'm planning on doing. I suspect the issue is that bearing are not being correctly color coded for whatever reason.

For the main bearings, check out the Toda bearings, I posted a bunch of photos in my engine thread. They are pricey but amount to almost nothing compared to the cost of building a C30.
 
Last edited:
Back
Top