Front Cylinder Head Cam Journal Failure

More than likely most of you have seen this already, but I'm reposting it here just to make sure I'm not missing anyone.
I recently had a front cyl head intake cam journal wipe out. The car has never been tracked, but it has sat in storage with only intermittent use over the past 15 years. Oil pressure is good. What I don't know is the type of oil that has been used in the car.
Apparently this is not an uncommon failure, but so far everyone appears to be guessing as to why its happening. Where I did my repairs there is another NSX with the same failure. The failure is always occurs on the front head exh cam. One thing to keep in mind is that this area is the last area to see oil pressure on startup.
In the hope of preventing it from happening again I am using only top for the line oil (Penzoil Ultra Synthetic 10w 30w) and I have installed a baffle in the oil pan. One more step I could take is going to a high efficiency oil pump and then using a 5w 30w oil.
Anyone other than the few I already know about have this problem, and what are your opinions on what caused it?

This is pure conjecture; but, based upon the fact that the engine has some pretty tight clearances, high viscosity oil is not necessarily your engines friend. The wiping of the journal could be the result of repeated start-ups with a high viscosity oil that caused low oil flow to the journal during the initial start up period. This of course assumes that high viscosity oil was used in the engine at some point.

I have also had this happen. My best guess was that I put some high G loads on the car after installing new sway bars and then proceeding to put the car under load for testing. But the only solution that makes sense is dry slumping the system. Guess how much that can set you back! Unfortunately, I've only seen a few examples of this being done, and none were affordable and all came with other issues.

Juice said:

I have also had this happen. My best guess was that I put some high G loads on the car after installing new sway bars and then proceeding to put the car under load for testing. But the only solution that makes sense is dry slumping the system. Guess how much that can set you back! Unfortunately, I've only seen a few examples of this being done, and none were affordable and all came with other issues.

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Or, you can do an Accusump setup. There's a brand-new TiDave kit for sale in the classifieds section right now that is basically a plug-n-play system once you find a place for the canister :wink: I'm selling mine because I indeed went with a custom dry sump. But, is an extra $2k over an Accusump worth it? A dry sump has problems as well from unreliable scavenge pumps to belts slipping off. It's not a trouble-free system either.

Another benefit by the Accusump is the ability to pressurize the oil galleys before startup.

Dave

Oil sump baffles are probably a no risk modification. Accusump and dry sump are good solutions that may bring some attendant risks (more maintenance or stuff to break). That said, the OP said the car had not been tracked though was silent on whether it had been subject to super keener driving. If the problem had been oil starvation due to high G loading, I also would expect that the main bearings would take it on the chin first. The camshaft bearing surfaces have a lighter loading on them than the main and con rod bearings. If the problem was a general loss of oil pressure, I am having difficulty coming up with a scenario where the mains are OK and the cam journal (and it looks like just one journal) is damaged.

As I recall, the NSX has orifices between the block and the head which I believe are used to control the flow of oil to the heads. High viscosity oil messes up the flow through the orifices, or if a chunk of something (gasket / sludge / gasket maker?) gets in the orifice you could have a starvation problem. I offer no observation as to why this only seems to occur on the front head (maybe we don't hear about the rear head failures?) and why it looks like only one journal was damaged.

Old Guy said:

This is pure conjecture; but, based upon the fact that the engine has some pretty tight clearances, high viscosity oil is not necessarily your engines friend. The wiping of the journal could be the result of repeated start-ups with a high viscosity oil that caused low oil flow to the journal during the initial start up period. This of course assumes that high viscosity oil was used in the engine at some point.

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What type of oil used unfortunately is a mystery. I think with the type of oil and it sitting for long periods is what probably did it in.

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Old Guy said:

Oil sump baffles are probably a no risk modification. Accusump and dry sump are good solutions that may bring some attendant risks (more maintenance or stuff to break). That said, the OP said the car had not been tracked though was silent on whether it had been subject to super keener driving. If the problem had been oil starvation due to high G loading, I also would expect that the main bearings would take it on the chin first. The camshaft bearing surfaces have a lighter loading on them than the main and con rod bearings. If the problem was a general loss of oil pressure, I am having difficulty coming up with a scenario where the mains are OK and the cam journal (and it looks like just one journal) is damaged.

As I recall, the NSX has orifices between the block and the head which I believe are used to control the flow of oil to the heads. High viscosity oil messes up the flow through the orifices, or if a chunk of something (gasket / sludge / gasket maker?) gets in the orifice you could have a starvation problem. I offer no observation as to why this only seems to occur on the front head (maybe we don't hear about the rear head failures?) and why it looks like only one journal was damaged.

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Cody Loveland at LoveFab has seen several of these failures. The opinion is that there is the possibility that there is an inherent flaw that Honda never documented. I checked all the passages and everything was clear. The orings on the orifices were also intact and in good shape, but I replaced them anyway. The other car in the shop that had the same exact failure was tracked and we think the pump cavitated, but again we can't be sure. Cody did agree that the Accusump was good insurance, but it like you said it does come with maintenance concerns. Best bet to help limit the possibility of it happening again is the baffle I installed and using a top grade oil. I am considering going with the high efficiency pump and using 5w 30w oil. 5w will flow faster on start ups.

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Mac Attack said:

Or, you can do an Accusump setup. There's a brand-new TiDave kit for sale in the classifieds section right now that is basically a plug-n-play system once you find a place for the canister :wink: I'm selling mine because I indeed went with a custom dry sump. But, is an extra $2k over an Accusump worth it? A dry sump has problems as well from unreliable scavenge pumps to belts slipping off. It's not a trouble-free system either.

Another benefit by the Accusump is the ability to pressurize the oil galleys before startup.

Dave

Click to expand...

An accusump is a possibility. Even before knowing it existed I was wondering of someone made a pre-oiler. They were common on high performance piston engines in aircraft. I did hear that there were some maintenance issues, but not sure what.
I'm also considering going with a high efficiency oil pump and then using 5w30w oil instead of 10w30w.

I've used 5W30 for the last 7 years mine was running. The last 3 years and 400 miles has been with 10W30 Joe Gibbs break-in oil....

An oil pump is a very expensive modification due to labor (TB has to come off) and the parts themselves. Also, there is no "high-efficiency" pump. The gerotor design is the same for all of them. They are made of different materials, or are wider gears in a machined-out OEM housing to flow more oil... that's it. Overkill for a street car in my opinion if your OEM pump is in good shape.

Honestly, I think an Accusump is overkill for a street-only car too. The only thing I would do to yours is run a good synthetic 5W30 oil like you are planning to and change it regularly.

The baffle doesn't do too much. A proper baffle has hinged trap doors to allow oil to quickly reflood the pickup.


This reminds me of someone else on this forum a long time ago - Jeffshoots - who said the main bearing had a critical oiling design flaw. Now, this is someone who bought an older used car with a lot of miles on it without documented history of regular oil changes (non-synthetic back in those days too), beat it on the track, and ruined a main bearing. I mean, you can't be too surprised... Putting synthetic oil with powerful cleaners through these engines after it's been gunked up with old non-synthetic oil is a recipe for disaster and could have been the cause of your issues as well - not necessarily an undocumented Honda design flaw!

So, how do you fix this?

Depends.

The one in the picture above was probably just lightly sanded and polished. It didn't look too bad but it is hard to tell from a picture.

Otherwise, the more in-depth repair costs (grinding all cam caps and line-boring, or welding/boring the one journal) have to be considered relative to just replacing the head.

Front Head Intake Cam Bearing Failure Update

Just want to provide an update to anyone following this thread. I could never find a definitive answer to the cause of the bearing failure, but I suspect that it was combination of the type of oil used, the time the car sat idle between startups and possibly colder air temps when the car was started. From 2001 to 2014 approximately 6k miles was put on the car, so use was infrequent. I didn't want to search from someone to re-machine the head or rely on the finished product, so I decided to replace the head. I was lucky to find a new head at reasonable price. Internally the motor was spotless other than a few locations in the top of the head were oil gets trapped. There were no obstructions in the oil circuits to the cams. After the new head was installed oil pressure to the cam and crank was measured at >100psi so oil flow/pressure is not an issue. I am now using the new as of 2014 10/30 Penzoil Ultra Platinum Synthetic Oil (made from natural gas). This oil currently has the highest load carrying capacity rating of all the oils currently available at 116,612 psi @ 230deg. At the next oil change I might change to 5/30 oil to insure faster lubrication to bearings during startup.