Big end bearing failure, fixing and cleaning up afterwards

[1600Dave]

So, looks to me like I have done a big end bearing on the skidpan at Eastern Creek last night. Very loud rattle / knock comes in around 2000 rpm and also happens for a second or so at startup.

The engine will be coming out in the next few days to see how bad the damage is and how to best proceed (rebuild current engine or throw in a second hand one). My main question revolves around how to best clean up after any bearing metal went through the engine if I go down the recondition route. I'm more used to Datsun engines, standard practice is to drill out the pressed-in soft plugs in the oil galleries, clean them out thoroughly , then replace with a tapered screw-in plug. Is there an equivalent procedure for MX5 engines ? If so, is it documented anywhere, outlining any gotcha's ? Or just poke around randomly in any obvious galleries, hot tank it and hope for the best ?

While I'm asking, anything else I need to be aware of ?

Any recommendations as to where to buy bearings / gasket kits / etc ?

EDIT: Standard NB8B engine

[manga_blue]

The head has tapered screws plugs to let you into all the galleries, I can't recall what's on the block though.

In any case wouldn't the filter stop any stray metal from getting into the system?

A rebuild is only worth it if you want to do some mods to the engine along the way, like dynamic balancing, oil pump upgrade, head work, stronger rods, etc. Otherwise just throw in a replacement and save the old motor for a project.

[noobee]

so long as you get a good 2nd hand motor,I agree.my son bought a 2nd hand vvt engine for a turbo build.it supposedly had 70 or 90 thousand k's on it(guy wasn't sure,but he originally bought it of lou,boyracer).when it was apart for rods,studs,acl bearings etc,I measured everything as we went and it all measured up within new tolerances!
Mick

[1600Dave]

Thanks guys. Yep, still undecided on 2nd hand or rebuild - I probably wont make a decision until I strip the engine down and see the damage (ie can the crank be economically saved, how is the head for hardness, etc).

I guess the oil filter should catch most debris. Maybe I'm just a bit paranoid coming from a background of playing with old Datsun engines, and needing to open up the galleries to get 40+ years of built up filth, caked up oil and general detritus from not being serviced out when doing a build.

[madjak]

I just did a big end bearing on my race engine... process for cleanup was a little time consuming but nothing hard and can easily be done with a few basic tools. It's quite enjoyable to pull down an engine and rebuild it and gives you great knowledge of the engine and how it works. The machine costs are probably the biggest component.

here is what I did:
Pull the head off the block and then the entire block apart and clean thoroughly with lots of degresser, high pressure water (karcher) and then dry with high pressure air. Spray into all the oil passageways etc and try and flush out any shavings. You don't have to pull off the cams or valves in the head, but remove as many bungs as you can and get into all the oil journals and clean them out as best as possible. The crank, if it's still usable will need to be machined to a larger thou clearance and then cleaned thoroughly. You also need to pull out the oil pump gear and clear out the oil pressure relief valve.

I had an oil cooler so I also flushed all my oil lines and spent 30 mins cleaning out the oil cooler. I ran high pressure degreeser through it from lots of different directions, hooked the hose up and flushed it for ages. I dried it out with an air gun, let it sit for a day or to and flushed it all again.

Whilst the engine was apart, I had the cylinder bores honed and I installed new rings. I also refreshed all the seals and gaskets over the entire engine.

You'll need:
Crank machining - $250 (new cranks can be sourced from BP astina / protege / 323 engines cheap)
Block honed - $120
Engine seals, gaskets etc - Around $250 worth from Amayama
New bearings (crank, big end, thrust) - $140
New rings (may as well) - mine were $100
2 x cheap run-in oil and filters - $60
2 x good oil and filters - $120

All up around $1000 for what is basically a complete refreshed engine.

I ran the engine for 5-10mins reving it gently and getting it up to temp. I then shut it down and changed the oil and filter. This was to check oil pressure and flush anything I missed out of the block / head. I did get a little bit of water show up in the oil when I drained it... probably left in the oil cooler or something.

I then ran in the rings for 15 mins on the road. Running the engine up to revs and then compression braking back down. I shut it down and changed the oil and filter whilst hot. At this point I filled it with synthetic and went off the next day to a track event... spending the first few sessions slowly building up revs and pace until full pace by the end of the event.

I did one final change of oil and now I'm happy to run my standard oil program.

I also went out and purchased a longacre oil pressure gauge with 3 levels of warning lights. I figured it was good insurance.

[1600Dave]

Wow, detailed reply - much appreciated.

That was pretty much my initial thoughts - spend up to maybe $1500 and get a known fresh engine (assuming its not too badly damaged, I did drive it home to Newcastle from Eastern Creek and it has a decent knock now ). Once rebuild cost goes higher, I guess the 2nd hand option starts looking good. Having said that, I intend keeping the car indefinitely and it is used for supersprints and regularity so a good engine would be one less thing to worry about. But then I like tinkering, building engines in the shed is very therapeutic. Decisions, decisions.....

Handy to know about other sources for a crank. Am I right in assuming that the crank in the vvt engine is no different to other 1.8 cranks ?

[StillIC]

I did drive it home to Newcastle from Eastern Creek and it has a decent knock now.

Many a year ago (~12 of them) I drove my Celica from Eastern Creek to Newcastle with a knock. At home I pulled the big end bearings, cleaned the crank with 2000 grit wet and dry in oil, installed new bearings, and it is still running well to this day. It was much cheaper than a tow!

[madjak]

If you've been driving it with flakes in the oil, some might have gotten through the filter and into the head / block. You should probably pull the cams and check the cam bearing surface in the head. If there is any scouring then that's the point the engine is dead and to replace with a new one. Cranks, rods etc are all common enough that they are fairly easy and cheap to pick up.

I forgot to add that you'll most likely either need to replace the rods or machine them as well as the crank, depending on how much hammering has been taking place. From your description and given you drove it home, I'd guess both are now past repair. You can either pick up some spare rods easy enough from someone... (I have a couple of sets of OEM NA8 rods) or go on ebay and buy a set of forged rods for $350. If you are keen, go grab an engine out of a Protege and you can use crank and rods from that, plus other spare bits.

My understanding is that the crank and rods are the same on all BP engines. Pistons on your engine will be higher compression than earlier models but should work on any rod. Someone else might chime in on this.

PM me your details and I'm happy to talk you through it all via the phone. btw... here is what your bearing will most likely look like: Mine is hanging up on the trophy wall of damage in my dad's workshop.

[madjak]

I did drive it home to Newcastle from Eastern Creek and it has a decent knock now.

Many a year ago (~12 of them) I drove my Celica from Eastern Creek to Newcastle with a knock. At home I pulled the big end bearings, cleaned the crank with 2000 grit wet and dry in oil, installed new bearings, and it is still running well to this day. It was much cheaper than a tow!

Probably had a bit more power too because everything was a tad looser! When I did my bearing I was at 8300 rpm for part of a lap before I slowed down and heard the whine... as I slowed down in the pits the whine turned into a tick and I knew it was all bad.

[1600Dave]

I drove my Celica from Eastern Creek to Newcastle with a knock..... It was much cheaper than a tow!

That was my logic . Getting a tow back to Newcastle at 9pm on a Tuesday night (twilight motorkhana) wasn't looking like a lot of fun. Or cheap. Doing 70kph all the way home wasn't fun either, but keeping it below 2000rpm in 6th made the knock go away. Or at least be less worrying.

Probably had a bit more power too because everything was a tad looser!

My father (a bike racer from way back) had a favourite saying "They always go fastest just before they blow up". From the amount of remnants of old bike engines we dragged out of his garage when clearing his house, it looked like he tested that theory quite a bit.....

PM me your details and I'm happy to talk you through it all via the phone.

Much appreciated. I may just take you up on that once its out and dismantled.

I had thought cheap ebay rods would be the go, the cost of getting the stock ones resized would probably go close to the price of new ones. Last Datsun engine I built, it was actually more expensive to get stock rods resized, shot peened and balanced than new h-beams off ebay

[madjak]

I had thought cheap ebay rods would be the go, the cost of getting the stock ones resized would probably go close to the price of new ones. Last Datsun engine I built, it was actually more expensive to get stock rods resized, shot peened and balanced than new h-beams off ebay

Finding a good crank is the hardest part, and generally when you find the crank you get the rods for free. But yes, the ebay rods are cost effective and fine for all but the highest end builds.

Do you know what caused the bearing to fail? You said skid pan, so I assume you were giving it lots of revs for a sustained period. Do you know if you lost oil pressure or not, because the oil pumps themselves can fail. I guess the oil pump would be fine if you managed to drove it home.

[1600Dave]

No idea why it went. It was a run-of-the-mill motorkhana on the wet skidpan, only difference was that the last course of the evening was on the full skidpan so high revs sustained for longer than normal. I parked it after the last run without noticing anything, packed up and when I started it up to go home it rattled for a second or so. Then a few k's later, it developed a knock at rpm's above 2000 on a constant throttle (under load or a trailing throttle showed no symptoms). It was fine under 2000rpm's (well, the knocking wasn't audible at least). Oil level was good, I always give it a check before an event. Just one of those things I guess, the price of hitting the track (or skidpan in this case).

[manga_blue]

No idea why it went.

VVT engines had an upgraded oil pump to handle the extra load from the VVT actuator. It has been found to be a bit more fragile ...

[1600Dave]

Another thing to check, thanks !

It didn't lose oil pressure. Well, it had enough pressure to keep the "gauge" showing pressure - a real gauge would be nice.....

[1600Dave]

Finally got around to ripping the engine out. Carnage was very mild

#2 big end bearing has spun, and has been pounded out a little (its about 2mm wider now). Crank is slightly scored but not too bad, likewise the rod. Crank would clean up but I'd buy another set of rods.

Regardless, found a cheap low mileage engine, so that will be going in on the weekend. The original engine will then be rebuilt at my leisure and kept as a spare.

Bad bearing on right and at top, good bearing on left in pic.

Made a horrible rattle though !

https://www.youtube.com/watch?v=9-iFFmTyXvA

https://www.youtube.com/watch?v=5NWII7WXOdI