Why am I destroying rod bearings?

[axelbaker]

I've had my 81 Spider for 2 years in January. Bought as a non-runner. Last winter I pulled the engine, and tore it down. (If you want too much detail, read my resto-thread)

The car is used as a weekend run about. It's been running fine since the engine went back in. I've put about 4000 miles on since the motor went back in. Mostly canyon runs in the Berkeley Hills or up Highway 1 in Marin.

While doing a run up a 10 mileish twisty at high rpms, I heard what sounded like rod knock. Not as loud as what lead to removing the engine last time, which required a crankshaft regrind. So I called it a day and drove home about 5 miles (yes, I know).

I had not got around to installing an oil pressure gauge. The oil light goes out instantly on startup. (I of course bought a gauge put it on the to-do list and then never got around to it, expensive mistake)

Draining fluids didn't reveal any thing, and cranking the engine just past TDC on each piston and pushing on it with an long long extension didn't seem to reveal any movement in rods.

An oil and filter change cured it till it came up to temp again.

Upon cutting open the old filter I found fine bearing shavings. So I guess I am at the least doing bearings again. Hopefully not the crank.

The sump will come of some time this week for a proper inspection.

My question is am I exceeding the oil system on this motor? I was flogging the car. Drifting corners and running over 6000rpm for almost 10 miles. I would expect a motor that won WRC 10 times, to be able to do that.

Am I pumping all the oil in to the head? I have an OEM baffled sump, but it's not exactly sophisticated. I want this car to be able to play with it's Miata grandchildren. Do I need to start upgrading the oil system? GC style winged sump? Restrict the oil flow in to the heads? Open up the drain back from the head?

Thank you in advance.

[SteinOnkel]

Hmm hmm hmm.

I doubt that you are exceeding the oil system. As you said, the engine won WRC 10 times. It's not a bad engine at all.

This may be a long shot, but perhaps you used the wrong bearings? Too big, too small, causing them to spin?

As for the baffling not being sophisticated, that goes for 99% of all baffled oil pans. It's just simple sheet metal, really. I've run my VW I4 without baffling on the track many, many times. Never had an oiling issue. On today's episode of Apples - how do they stack up against oranges? I digress.

How about oil temps? Do you have a cooler, gauge? What oil are you running?

[18Fiatsandcounting]

These engine love to rev, and 6000 rpm for hours at a time is child's play for them. In addition, as SteinOnkel alludes to, the oil system is more than sufficient to take almost any abuse.

It would probably take some forensics work to figure out what is really going on, but from what you've described, it sounds like you've got some wrong parts in the engine. Wrong bearings, connecting rods, oil pump/filter, or the like.

-Bryan

[Nut124]

Axel, sorry to hear about your troubles.

The bottom end of this engine has a reputation of being most bullet proof. As you stated this engine was used in WRC with good success in the 70's. 6000rpm is just a start.

The 2L cranks are not supposed to to be reground. The 2L cranks have a surface hardening that should never need grinding. If they do, something else is wrong and the hardening is lost.

Did you plastigauge the brgs?

[gbsailing]

one quick question did you recondition the rods or just reuse them?

[axelbaker]

Well, I suppose this is good and bad news.

The car and motor are effectively factory stock.

The engine came out last time because the PO broke the aux shaft and half of it was sitting in the pan, so while the engine was bleeding internally it was run for an unknown time and burned the #4 rod bearing and wore the journal by a few thousandths.

I had #4 welded and reground to stock dimensions. The other journals were NOT reground. Yes, i know the crank is nitrided. All my tolerances were measured and with in spec of factory. Every thing miced and plasti-gaged multiple times. Multiple dry builds were performed. I made spreadsheets of almost every as built dimension in the engine.

The rods were measured and were well with in tolerance. They were not reconditioned. I broke in the motor with cheap oreiley 10w40 for 100 miles then again at 500. I cut open the first oil filter after the build and it was clean. After brake in I switched to Mobil 1 0w40. It had about 2000 miles on that oil change when the motor failed. Oil level is checked almost ever time it's driven.

I do not have an oil cooler installed. The oil pump is OEM and has been torn down measured with in tolerance and the filter was the big bosch.

The engine runs at about 190f off the water gauge. On hot days or long runs it climbs a bit, maybe 205f.

Well I guess it's time to start unbolting motor mounts.

[SteinOnkel]

"I had #4 welded and reground to stock dimensions."

I suspect that this is where the issue lies, unfortunately.

There seems to be a giant gap between machinist and engine builders in these parts. I'm still on the lookout for a good one to hone my VW block and balance the rotating assembly. So far, nobody local is up to snuff. You walk into the shop, it's dimly lit, there's shit everywhere, place hasn't been swept in weeks. No, thanks. Anybody worth the money is booked for 10 weeks out, minimum.

Don't feel too bad, Axel! I had the same thing happen this year with my Fiat transmission rebuild. Sunk $750 in parts into the damn thing and it was worse afterwards.

[18Fiatsandcounting]

Anybody worth the money is booked for 10 weeks out, minimum.

Agreed. Two things are going on: 1) with modern car engines rarely needing to be rebuilt (people just sell the car and buy another, plus better designs), the "corporate knowledge" of how to build an engine is slowly disappearing, and 2) under COVID, racers are racing, but without the crowds to bring in money, they aren't doing a lot of preventative maintenance and so they run the engines until they break. My machinist tells me he's spending a lot of time fixing engines with problems that should have been avoidable.

OK, I've diverted this thread enough, so I'll stop there. For Axel, you might need to find a new crankshaft if you want the engine to run happy at 6000+ rpm. Before you go that far though, try finding a few second opinions from engine builders.

-Bryan

[SteinOnkel]

There is (was?) an old dude in Stockton parting out a 124 a few weeks ago. I bought a spare transmission from him for cheap. He did have an engine there (just block and head) from a '75 that rotated just fine. I bet Axel could get it for $100. Might be a better starting point for the next rebuild.

[Nut124]

Axel, did you say you ran 0W-40 oil? I think that is way too thin for an older engine like this Fiat. How did you determine it was OK to run such thin oil?

I anyone else here running 0W or 5W oils?

I run 15W-40 or 15W-50.

Also, if the aux shaft broke, then it was out of time and got hit by the crank. This likely damaged the aux shaft bearings in the block. If these are bad the engine does not develop good oil pressure.

[18Fiatsandcounting]

Is anyone else here running 0W or 5W oils?

I have always run conventional 10W-40 out here in California, and when I lived in colder parts of the US in the past, 10W-30. Never had an oil-related issue as far as I could tell, but I also don't drive that hard.

-Bryan

[SteinOnkel]

Is anyone else here running 0W or 5W oils?

I have always run conventional 10W-40 out here in California, and when I lived in colder parts of the US in the past, 10W-30. Never had an oil-related issue as far as I could tell, but I also don't drive that hard.

-Bryan

But why?

[18Fiatsandcounting]

Is anyone else here running 0W or 5W oils?

I have always run conventional 10W-40 out here in California, and when I lived in colder parts of the US in the past, 10W-30. Never had an oil-related issue as far as I could tell, but I also don't drive that hard.

-Bryan

But why?

For an engine based on 1950s / 1960s technology, I don't see the need to run synthetic oils. For modern engines that specify a synthetic oil, sure, but for my Fiats that only get driven 500 miles per year or so, plain ol' conventional 10W-40 seems fine.

-Bryan

[aj81spider]

I use 15W/40 because that's what the owner's manual says to use. I've never had an issue either.

There is a large school of thought - that I do not have the expertise to confirm or deny (but it's on the internet so it must be true!) - that synthetic oil shouldn't be used in older engines because it leaks more.

I haven't spent too much energy on that, as I figure if I'm using what the engine designer intended and I'm not having any problems I'll be OK. Given that the spec was for 15W/40 a 0W oil would make me a little skittish (perhaps with no good reason, but I'm happier not being skittish).

[18Fiatsandcounting]

...that synthetic oil shouldn't be used in older engines because it leaks more.

My understanding is that synthetic oils won't leak any more than regular oil, IF the gaskets and seals are in good condition. That last phrase is important, and apparently synthetic oils (because of their lower viscosity and smaller average molecular size) will tend to leak more out of seals and gaskets that are marginal. So, with an older engine with minimal leaks with a conventional oil, it's quite possible to see some additional leakage with a synthetic oil.

I too would be wary of using a zero weight oil in a Fiat engine. The engines simply weren't designed for this.

-Bryan