'95 3.0 big ends

[ukspeed]

Sadly my baby - '95 UK 3.0 manual - suffered oil starvation whilst on track recently and the result is loud knocking from the big ends, no question the bottom end will need some surgery. So.....

Has anyone been down this route before? I can't really afford to splash out £6k on fitting a replacement unit and besides there is nothing fundamentally wrong with the rest of the engine; so I was hoping I'd be able to have a quality engineering shop dismantle, replace the crank & big end bearings with a crank regrind as necessary and put it back together. OK I realize I may be oversimplifying things a little but I worked in an engine shop some years ago and essentially thats all that should be required as far as I can see - am I being niave or is there more to repairing the NSX motor than meets the eye?

Any constructive advice appreciate!

(Its only been a week and I can't believe how much I'm missing the car already!!!! :redface: )

 

[Dave Hardy]

Depending on how bad the damage is, and how "wrong" you're willing to be, it can be very cheap. My race engine, which is regularly spun to 8000+ RPM has done so for the past 2 years after a "ghetto" rebuild after a spun bearing. Read about the failure at http://www.dilysimotorsports.com/engine.htm. I did a bit of filing to the crank to knock off the high spots, polished it in the car with 120, then 240, then 400 grit sand paper off of 1" rolls, bolted a new bearing in along with a used rod (original was bent) and put it back together. I even reused the headgasket. I had about $50 total in the rebuild, most of which was in the 3 oil changes within the first 10 minutes of startup.

 

[Cees-Jan]

With some luck you will have the same as Dave, you can see on the pics that the Hardware off the NSX is quit regular except for materials.

Take her apart and post the pictures, if it is not repairable then put in a used engine.

 

[Larry Bastanza]

I think you must carefully check the cam journals and shafts. Oil starvation at the crack can mean there was little oil pressure up top too. As long as this checks out OK, then the bearing replacement/crank repair may do the trick.

I would seek the advice of NSXTech (Mark Basch). He has had to most experience about these repairs.

HTH,
LarryB

 

[ukspeed]

Wow, Dave that's a good story - and suggests the NSX bottom end is a tough old unit. I can hopefully take comfort in the fact that my engine siezed at idle with the clutch in after it'd made an unpleasant noise prompting me to select neutral. Hopefully I'll be able to just drop the sump, identify the offending journal and re-shell. Fingers crossed! Now then, where does one go about acquiring a pair of big end shells for a '95 3.0 UK?

 

[Dave Hardy]

Actually that repair was done in my lowly Civic. I'm not sure how the titanium rods will make the situation different, but I can't imagine it being all that much. As for the shells, I assume you mean the bearings. Shouldn't the local dealer be able to provide those?

 

[NSXTech]

The good news and the bad news is that all Honda motors use select fit bearing sizes for all crankpins. Its the good news because the fit is the best possible. Its the bad news because there are no bearings for repaired cranks. You can't go somewhere and buy .010 overs because they do not excist.
Honda puts all the care into the finish of the journals and then measures the finished size. That size is then indicated by a letter (or number) A-E (or 1-5).
The line bore in the block and the rod big ends are also measured and given a number. The bearings themselves have color assignments and bearing selection is done on a color chart. If, say, no. 1 rod end is a measured 3 and the corresponding journal is a B, then you look at the chart and select the bearing color under column B, row 3.

It takes a lot for a Honda crank to fail because of this. If you already hear a loud knock the rod is probabally damaged. Even if the backside of the bearing is still clean and no bearing movement is obvious, if you heard it knock it is very likely already out of round. This is why I reccomend if you are going to fix it, find a heavily experienced engine machinist, and if possible one with Honda exp. If the crank is bad, but all the rods are good, it will still cost at least 4k to fix. If it needs rods, they only come with pistons and are close to a grand each :frown:

Good Luck,
MB

 

[ukspeed]

It's becoming obvious to me that this repair (if thats what it is) will not be as straightforward as it would be on a more mundane engine. Obviously I'm not really going to know where I'm at until the engine is opened up (or at least till the sump is dropped) and a prelimnary visual inspection is done to guage the extent of the damage.
What I think has happened is this: one big end bearing has been run dry momentarily - sadly long enough to damage - and so I fully expect that bearing to be out of round. It sounds as though it'll be necessary to replace the rod & piston assembly: so be it, but working on the assumption that the bearing has protected the crank from damage how can I be sure which bearings will work with the old crank / new rod? Is this scenario even likely to work long term or is the engine effectively dead?
I do have an experienced engine builder who could take the job on for me, but he's only willing to work on the basis that it's a quality job "done right" which is heartening. Even better, I may have an NSX trained Honda mechanic who could do the job. Either way, I'm hoping to put together a solution which doesn't compromise the quality of the car post fix yet doesn't break the bank - I really can't afford to have it costing thousands and thousands.

 

[satan_srv]

Rebuilds are never what you expect to be. Like MB says if you know what colour bearings your stock motor is at, you'll have a good idea how much play you have. Like if your bearing is already a brown or black you might be in trouble (am I going the right way?).

Anyway on my h22a race motor we spun the bearing BAD. We had to throw the block away it was garbage..sleeves and all. What I'm saying is if you don't have an experience (w/ Hondas) machinist to work on it you may waste a lot of downtime and money getting it back together, and would have been better to just drop another engine and sell off the parts of your old one. (heads, good rods etc.). You need a guy that can drop the pan and the girdle and take a look and give you an honest opinion of rebuild vs. replace.

For fun here's a pic of my wrecked motor, nice crank eh?

 

[ukspeed]

I'm now looking for a good engine to put in my NSX - at the very least it will speed up the process of getting my car back on the road; I can repair the current engine at my leisure and sell on when repaired. Soooo....... does anyone have a good 3.0 manual engine (my car is a '94 UK car)?

 

[ukspeed]

:mission update:!!!

Well I've managed to locate an engine for a "reasonable" price, luckily a slightly lower mileage unit from a slightly newer car too. Can anyone advise on what will be needed to facilitate the swap? e.g, which gaskets will need replacing?
Presumably it'd wise to change the clutch friction plate whilst the engine is out - which non-OEM ones are good or am I best going down the OEM route? Is it worth looking at a change of water pump? (I've heard of these being a weak point).

 

[NSXTech]

Unless you know the tbelt and wpump on the replacement engine are fairly new, do these without fail. Also, if the three main hoses from engine to pipes on body are not new, make them so. Clutch if yours is half worn or more, unless funds are no prob- make that new too. If you don't have a service history on the car, do the valves regardless of tbelt.
Let me know if you have any probs or Q's.

MB