Possible cure for #2 bearing failure
 

So after putting more $$ into the money pit IE the Mistress by swapping out the bearing because I thought I heard the telltale sign of impending Bearing failure.
Turns I was right n caught it in time #2 top shell was down to the copper right under the rod beam. after breathing a sigh of relief I got to thinking there has to be
a way to fix or stop this so I did some internet research and came across an article on a 928 forum which basically stated Porsche drilled the crank wrong they put the
holes in the wrong spot. They should be a couple of degrees before TDC or point of max loading. There was a company that offered to redrill the cranks but they never revealed
what they did or how they did it but basically, they got the idea from GM where their big block motors were having the same failures at hi rpm turns out the oil passages had the oil
fighting centrifugal force the whole time oil hole is on the back side of the crank journal instead of the leading face.
https://cimg8.ibsrv.net/gimg/rennlis...f6a25aeb12.jpg
How our cranks should be drilled in blue.
https://cimg4.ibsrv.net/gimg/rennlis...02e1e43874.jpg
928 crank but take away on hole n you have a 944
https://cimg7.ibsrv.net/gimg/rennlis...c62a315dd3.jpg
So the question is can you block off the current oil passage and redrill the crank and not weaken the crank?
https://cimg5.ibsrv.net/gimg/rennlis...4fda77915c.jpg

the angling relative to TDC/max loading is interesting theory.

however dunno about the "centrifugal force" thing, heard it mentioned before...quick research of LSx, Ford 5.0, Ferrari, etc cranks show the rod oiling holes "off to the side" like the 944 crank rather than "pointing straight up at TDC"

Where I got my info
 

Where I got my info took me a while to find it

https://rennlist.com/forums/928-foru...igh-rpm-5.html

This is my kind of topic, so, glad to get into as deep as this rabbit hole goes, but....., when supposing the entire theory or inherent problem of the 944 engine is all due to centrifugal weighting of the oil supply, I wouldn't think it's wise to compare to a "fix" re. a GM big block with a stroke nearly an inch longer (more centrifugal effect) and a maximum power found at 5000 rpms.

What is the designated use of your car/engine....?
What model and displacement are we talking about...?

T

Like a machinist friend of mine says, "Drill it like a Chevy."

Well since I posted this in the 944 forum one could would assume I was speaking about a 944 engine. Bearing failure occur on NA's and Turbo a like... My Car is on it's 3rd engine due to #2 Bearing failure and all during road use to answer your question.
Gm had a issue with the big block engines torching the bearing just like the 928 and 944 their solution was to change the way they drilled the crank Porsche just stopped making the cars.
if you bothered to read the article I referenced stroke or size has nothing to do with it. It's physics and the laws of nature and design.
the 944 engine crank journals only receives oil under pressure once per rotation when the mains line up with the feed hole in the saddle. Oil exits the journal after making a 90deg turn when it wants to
go straight that oil also exits the journal aft of the center line of the connecting rod after the cylinder has fired. Also a 944 engine might generate high centrifugal effect earlier since they accelerate faster than a big block chevy when I say accelerate I mean engine rotation not vehicle speed.
Looking at the GM crank it receives pressurized oil twice per rotation as the engine spins faster that is less time that the journal's being fed pressurized oil and throw in the 944's windage problem n that just might be the source of the 928/944 oiling issue not saying I have the ultimate solution

I believe there should not be an engine #2 journal bearing failure if the engine is ONLY streeted and not tracked. Previously was the engine from a tracked car where the engine suffered a #2 rod bearing failure and was rebuilt with the same parts. Look for other issues that could cause the failure, ie not using the spec oil grade weight for that engine; the connecting rod orientation for that cylinder is not correct; the fat end of the connecting rod is out of spec; there is a restriction in the oil galley supplying oil to the #2 journal; there is too much clearance between the #2 rod bearing and the crankshaft journal.

https://cimg1.ibsrv.net/gimg/rennlis...70c85e0834.jpg
https://cimg2.ibsrv.net/gimg/rennlis...6e51e6d710.jpg
https://cimg3.ibsrv.net/gimg/rennlis...ebf69cd5af.jpg
https://cimg8.ibsrv.net/gimg/rennlis...4915af15e2.jpg
Car is not a track car bought it with a spun bearing so engine #1 bought an engine out of a wrecked running car engine #2 lasted from 2013 to last April bought an engine out of 87 NA which promptly **** the balance belt wedging it's self between the water pump and the timing belt taking the valves with it. Rebuilt head less than 50 miles heard the telltale tap tap while idling drained the oil plug covered in metal. I don't know where you get your info that it's a track car only problem. It's a sports car that's why we buy them it's been driven hard on the street and back mountain roads today tires offer significantly more grip than the tires that were available when the car was sold so you can generate 1986 race track cornering forces on the street with street tires and a good set up currently the car has 2011 911 stock rims 235 40 17 f 245 40 17 in back. Of course, ppl will say that's too much tire for the car but for the roads, I was using the car on I wanted tires that I couldn't overpower or over drive n send me off the side of a mountain... https://www.google.com/maps/dir/Tooe...307776!1m0!3e0
Poll enough owner on the site you will find your fair share of failures on the street.. Now my question to is do you have any ideas or solution that would help stop this from happening to track driven or street driven car??

Seems according to this thread that later (2.7, 3.0 ) engines with "windage ports" rarely suffer from bearing failure
https://rennlist.com/forums/944-turb...-5-blocks.html

Ahhh, a "944 engine". Well that narrows it down... :rolleyes:
It'd probably be useful for you to educate yourself further in the differences between the model and year variations before making an assumption that they are all the same.

Porsche practically priced themselves out of business in the late 80s/early 90s, GM was still building pushrod engines with cast iron components.
The oiling systems on the two engines have so many differences, there is no way to relate a "fix" from one design to the other.

Article....?
You linked a thread with "opinions", none of which have solved the issue to this day.
By the way, check my join date here...., I have already read every bit of data concerning oiling issues on 928, 944 and 968 engines that has every been typed on a keyboard.

What are you even talking about...?
The main journals have 2 feed holes each, less than 180 degrees apart.
The upper main bearing shell half has a continuous groove along it's entire surface.
The lower shell (in the girdle) delays the cutoff of oil supply past 180deg and begins it's feed again by approximately 10 degrees per side to make the total amount of time that oil is fed to the rod at least 200/360 deg even if it only had one oil feed hole in the main journal as you state, but it doesn't, it has two holes, which make the oil to the rod almost continuous.
There may be a a few degrees where oil is interrupted, a small oscillation between opposing main journals, but this could be corrected by using the fully grooved upper main bearing in the lower girdle position as well. Even at an idle rpm of 900 probably makes the issue moot. You are looking at static pictures and diagrams of a crankshaft on a table and thinking one dimensionally.

You lost me on that last bit,

T

LOL, exactly.

Which is why I asked what the purpose of the car use was.


Again, spot on. OP has had "3 engines fail",
Engine #1 he purchased car with blown engine, i.e., knows absolutely nothing about engine's maintenance, use, cause of failure.
Engine #2 he purchased used and it lasted 5 years from '13-'18.
Engine #3 has not failed but was caught in time and had bearings replaced.

T

Are you saying that all 944 engines are not just 944 engines....?

Changes and/or improvements that might make model and year relevant information...?

I wonder if OP has the late features, the upper crankcase sealing pieces, etc.

He didn't say.

T

Current engine is a 87 NA only difference I see is the auto tensioner and the balance shaft bearings and housing. If there are any differences other than that I am not aware please enlighten me?
#2 bearing failures are not specific to 944 engines the 928 which the 944 is loosely based of were prone to #2 and #6 bearing failures too they shared the same journal..
Having the original Motor rebuilt as a hybrid stroker Chevy pistons with Mitsubishi rods I did talk to the machine shop about cutting the windage ports in the block I got the idea from a motor cycle engine little did I know Porsche had Incorporated this feature into later engines. Think I will also go with some version on the Chevy oil passage in the crank having the oil exit the journal just before TDC and going in more of a straight line.

aussie944cab thanks for the link to discussion on the refitting of windage ports to old 2.5L motors

Been following this with great interest, especially since T offered his opinions on the subject too.

I've been under the impression for several years the #2 & (on the 928) #6 bearing failures were related to lateral forces induced by high G left turns of a longer than typical duration causing oil pump starvation and subsequent bearing failure? The conditions that seem to contribute to this type of failure don't normally occur except during track use? Is this no longer the theory?

lots of potential issues...
- oil pump starvation during long turns
- insufficient oil drain-back from the heads (serious problem on 928s)
- too many 90-degree turns in the oil galley after oil filter (filtered oil has a straight shot at #1 main and whats left goes to the other mains)
- OPRV bypass potentially allowing air bubbles into the pump feed
- AOS "return path" with potentially still air-entrained oil is right next to the pump pickup.

lots of fixes to try. dry sump certainly addresses many of them for the $$$$
- sump baffles
- slight vac in crank case (dedicated vac pump or dry sump scavenge)
- add external oil lines to feed the main galley more evenly after the filter?
- direct AOS drain away from pump pickup.

biggest first steps, IMO after breaking down a number of "failed" engines...
- better oil cooling
- better oil (xW50 minimum, not that 0Wx pisswater that Odurandina recommends)