944 S - should I or should I not replace rod bearings.

[NCGermerican]

Hey Folks. I'm hoping to get some advice on whether or not to tackle the rod bearings on my 87 S w/ 97K miles. I've owned the car for 2.5 years and unfortunately, there was no maintenance or repair documentation on the car when I bought it.

Basically, I'm nervous about taking the car to where it performs best - above 4,500 rpms. The main reasons are:

1) Cold start oil pressure is 5 bar but once it comes to operating temp, oil pressure is between 1.5 and 2 bar at idle. The pressure does increase to 4 or so upon moderate acceleration and I have not tested to see if it hits 5 bar at 5K rpm.

2) The car ticks. I have read many posts that the 16v cars are "very ticky", but mine gets faster with acceleration and when I let off the gas (shifting), the ticking is at it's fastest and most noticeable. The noise is not a clunk or a tap, but a definitive tick. I replaced all of the lifters when I had the head rebuilt and the injectors are rebuilt ones from 944online. The damper is genuine porsche with less than 1k miles. FPR is brand new and the correct 3.8 bar unit.

Just about the only mechanical items I have not replaced on the car are the rod bearings and piston rings. When I had the head rebuilt, the cylinder walls looked great and the car burns almost no oil between changes (VR1 20w50). The oil pan was replaced with the wrong one at some point (no oil level sensor bung). I would HOPE that if someone replaced the oil pan, they would have done the rod bearings as well, but no way to confirm. I do have the oil analysis kit from Blackstone.

My only other thought is an exhaust leak. I have an MSDS header and a Dansk cat-back on the car. I used new exhaust crush o-rings on the header and I used a new exhaust "donut" between the cat pipe and the muffler pipe.

So - should I go through the effort of replacing the bearings or is that a waste of time? Should I just have the oil tested first and see what the results say before digging in? What would you do?

[icb]

I would definitely test the oil either way, Dennis. Some people say that putting in new bearings without at least polishing the crank is silly and a waste of effort and money. Others seem to routinely change them after so many hours, miles, or races. If it were me, I'd probably go in there with new bearings in hand, and assess the old ones before just changing them. If they look worn but the crank is still very smooth and undamaged, change them. If they're perfect, you could just leave them in. You could even plastigauge the rod journals from under the car to find out how worn they are, and whether the rod bearings are the reason for the slightly lower hot oil pressure (but that could just as easily be the sender, gauge, or relief valve calibration) . If the bearings and crank are really messed up, well I'm not going to go there. Positive energy....
PS, the ticking you describe is strange. Have you ever pulled the oil pressure reducing valve in the head? I removed a bunch of silicone and what appeared to be o-ring debris from behind mine when I had it out. Maybe you're getting a bit too much oil pressure reduction!

[NCGermerican]

I would definitely test the oil either way, Dennis. Some people say that putting in new bearings without at least polishing the crank is silly and a waste of effort and money. Others seem to routinely change them after so many hours, miles, or races. If it were me, I'd probably go in there with new bearings in hand, and assess the old ones before just changing them. If they look worn but the crank is still very smooth and undamaged, change them. If they're perfect, you could just leave them in. You could even plastigauge the rod journals from under the car to find out how worn they are, and whether the rod bearings are the reason for the slightly lower hot oil pressure (but that could just as easily be the sender, gauge, or relief valve calibration) . If the bearings and crank are really messed up, well I'm not going to go there. Positive energy....
PS, the ticking you describe is strange. Have you ever pulled the oil pressure reducing valve in the head? I removed a bunch of silicone and what appeared to be o-ring debris from behind mine when I had it out. Maybe you're getting a bit too much oil pressure reduction!

Thanks Ian! I think as a first step I'll do an oil change this weekend and send a sample off to Blackstone. I'm going to be doing WP/Belts, etc anyway. I actually have a set of bearings, nuts and a new oil pan gasket. One of the reasons I'm hesitant to do the job if I don't need to is the oil pan gasket isn't currently leaking at all (knock on wood). I also have a brand new pressure sending unit - I may pop that in as well.

As for the oil pressure valve - It was replaced with a brand new one (I think it was over $500 just for that part) when I had the head redone 2 years ago. I'm going to see if I can get the ticking on video. It won't be easy since I need to be driving and shifting the car to get a good sample of the sound.

[stitch2k1]

97K miles

150k miles on my S2, and my original rod bearings were fine, but I still replaced them with ACL (better than OEM) bearings.

Basically, I'm nervous about taking the car to where it performs best - above 4,500 rpms. The main reasons are:

It's not going to die. Not driving it hard is actively damaging it. Redline a day keeps the mechanic away.

1) Cold start oil pressure is 5 bar but once it comes to operating temp, oil pressure is between 1.5 and 2 bar at idle. The pressure does increase to 4 or so upon moderate acceleration and I have not tested to see if it hits 5 bar at 5K rpm.

That's fine. If you're really nervous, hook up and eternal oil pressure gauge by removing the sending unit, but that's overkill. Are the leads for the sending unit clean? Is the cluster getting a good clean ground?

2) The car ticks. I have read many posts that the 16v cars are "very ticky", but mine gets faster with acceleration and when I let off the gas (shifting), the ticking is at it's fastest and most noticeable. The noise is not a clunk or a tap, but a definitive tick. I replaced all of the lifters when I had the head rebuilt and the injectors are rebuilt ones from 944online. The damper is genuine porsche with less than 1k miles. FPR is brand new and the correct 3.8 bar unit.

Are you mistaking injector tick for lifter tick? If it is lifter tick, put Liquimoly's lifter additive in. It's not snake oil like most and makes a difference, but works over 2-300 miles, not an instant fix.

Just about the only mechanical items I have not replaced on the car are the rod bearings and piston rings. When I had the head rebuilt, the cylinder walls looked great and the car burns almost no oil between changes (VR1 20w50). The oil pan was replaced with the wrong one at some point (no oil level sensor bung). I would HOPE that if someone replaced the oil pan, they would have done the rod bearings as well, but no way to confirm. I do have the oil analysis kit from Blackstone.

If your cylinder walls are not scored, do not touch the piston rings under any circumstance. Alusil is expensive and delicate, if it's fine leave it alone. I have an S2 motor in my garage I am rebuilding (was going to use, but now going to sell) and it's cylinder walls are fine so I'm leaving it, and same for the crankshaft bearings.
I would also recommend switching to Mobil1 15w50. VR1 has no detergents in it, because it's a racing oil. I still use it, but exclusively for track day events since it's less like a 20w50 and more like a 20w60.

My only other thought is an exhaust leak. I have an MSDS header and a Dansk cat-back on the car. I used new exhaust crush o-rings on the header and I used a new exhaust "donut" between the cat pipe and the muffler pipe.

What does the exhaust have to do with oil pressure and rod bearings

So - should I go through the effort of replacing the bearings or is that a waste of time? Should I just have the oil tested first and see what the results say before digging in? What would you do?

You've already made up your mind you need rod bearings. It's not that bad of a job, get the correct oil pan (and appropriate drain tube and pick up tube) and just do it. I would recommend a baffled oil pan since you are swapping anyway.

[NCGermerican]

150k miles on my S2, and my original rod bearings were fine, but I still replaced them with ACL (better than OEM) bearings.

I'd need to look into the ACL ones. I bought a set of glyco bearings a few years ago and they've just been sitting in my garage.

It's not going to die. Not driving it hard is actively damaging it. Redline a day keeps the mechanic away.

I know. I need to find a good place near my house to open it up and gain the confidence that it won't spin a bearing.

That's fine. If you're really nervous, hook up and eternal oil pressure gauge by removing the sending unit, but that's overkill. Are the leads for the sending unit clean? Is the cluster getting a good clean ground?

Yeah I cleaned all the grounds under the dash - including the ones way back by the underside of the fuse panel. Those were fun. I also cleaned up all the connections on the back of the gauge cluster. It didn't seem to make a change to the oil pressure reading, but it solved my "full tank but only 3/4 on the gauge problem"! I have a brand new sender that I'll put in this weekend to see if that changes anything.

Are you mistaking injector tick for lifter tick? If it is lifter tick, put Liquimoly's lifter additive in. It's not snake oil like most and makes a difference, but works over 2-300 miles, not an instant fix.

On mine, the lifters make more of a "clack" than a "tick" when the car sits for awhile. It goes away after I run it for a few minutes. The tick issue could very well be the injectors doing their thing.

I would also recommend switching to Mobil1 15w50. VR1 has no detergents in it, because it's a racing oil. I still use it, but exclusively for track day events since it's less like a 20w50 and more like a 20w60.

I didn't realize that about VR1. It's probably the most recommended oil for 944's that I've read online. Does the M1 15w50 have the recommended zinc content? I used to run Driven 0w40 but in the NC summer heat my oil pressure was even lower.

What does the exhaust have to do with oil pressure and rod bearings

In the event the tick sound is an exhaust leak

You've already made up your mind you need rod bearings. It's not that bad of a job, get the correct oil pan (and appropriate drain tube and pick up tube) and just do it. I would recommend a baffled oil pan since you are swapping anyway.

I haven't made my mind up yet. If the oil analysis comes back good, I'll probably let it go for now and use the bearings on my 951.

[500]

With my '87 S, I had the same thought as you, that my oil pan must have been changed as it did not have the oil level sensor bung. It gnawed on me though, as there was nothing else about the car that suggested it had been opened up to that degree.

Eventually, I realized that the new pan was actually a running change in 1987. PET shows that for S engine numbers below 42H 03027, the pan is 944 101 201 11, which is the old style pan. My engine number is 42H 01802, so the old pan makes sense after all. However, the wiring harness did have the connector for the sensor. I think what likely happened is that Porsche elected to first use up the stock of old design pans, which I guess makes sense, as they certainly must be one of the more expensive oil pans out there!

oil pan.png (284.82 KiB) Viewed 275 times

[icb]

I didn't realize that about VR1. It's probably the most recommended oil for 944's that I've read online. Does the M1 15w50 have the recommended zinc content? I used to run Driven 0w40 but in the NC summer heat my oil pressure was even lower.

Whatever oil you decide to run, you'll want to make sure the molybdenum is there for the cylinder walls as well as the ZDDP for the camshafts. I run Driven DT40. You're in a hotter area, so you could run the thicker DT50, especially in the summer heat. Here in Dayton, DT40 is good for 2-2.5 bar at idle in 90 degree summer heat after running for 30 minutes on the highway at 75-80 mph or so (944S, 135,000 mi). Run the thinnest oil (per the Porsche manual) your conditions permit, or you're just giving away HP, something we can't really afford to do. There is some new oil analysis info at Speediagnostix.com and other Alusil-specific lubrication information at LNEngineering.com, if you haven't already seen it.

[NCGermerican]

With my '87 S, I had the same thought as you, that my oil pan must have been changed as it did not have the oil level sensor bung. It gnawed on me though, as there was nothing else about the car that suggested it had been opened up to that degree.

Eventually, I realized that the new pan was actually a running change in 1987. PET shows that for S engine numbers below 42H 03027, the pan is 944 101 201 11, which is the old style pan. My engine number is 42H 01802, so the old pan makes sense after all. However, the wiring harness did have the connector for the sensor. I think what likely happened is that Porsche elected to first use up the stock of old design pans, which I guess makes sense, as they certainly must be one of the more expensive oil pans out there!

oil pan.png

Holy cow that answers a lot of questions. I just assumed because I had the connector for the oil level sensor that someone swapped in another pan.

[stitch2k1]

On mine, the lifters make more of a "clack" than a "tick" when the car sits for awhile. It goes away after I run it for a few minutes. The tick issue could very well be the injectors doing their thing.

It's probably injectors. Don't lose sleep over it.

I didn't realize that about VR1. It's probably the most recommended oil for 944's that I've read online. Does the M1 15w50 have the recommended zinc content? I used to run Driven 0w40 but in the NC summer heat my oil pressure was even lower.

Yes. The Mobil1 has been around since these cars came out. I know of a Turbo '86, original owner car, had ran it since new just about. Motor blew up due to idiocy, and that car is unfortunately still having issues. It's been meaning to come up to me to get checked out.

I haven't made my mind up yet. If the oil analysis comes back good, I'll probably let it go for now and use the bearings on my 951.

I am doubtful oil analysis can tell you anything about rod bearing wear. And to the above, use ACL.

Eventually, I realized that the new pan was actually a running change in 1987...the wiring harness did have the connector for the sensor. I think what likely happened is that Porsche elected to first use up the stock of old design pans, which I guess makes sense, as they certainly must be one of the more expensive oil pans out there!

The harness update happened late MY86. I've seen more than one MY86 with the wiring for a oil pan level sensor.

I run Driven DT40.

5w40? Yikes. You don't have the film strength necessary for the motor. The oiling system of the 944 (every pre-996/986 Porsche motor) is throwing crap at the wall and seeing what sticks, especially in a 16 valve. If you don't have adequate (high film strength) oil the camshafts will start failing almost immediately (on the lobes, and sprockets, especially on a 968 due to variocam stress). You can have all the ZDDP you want, but inadequate film strength means it was all for nothing.
And there is no spec sheet on their website?

[icb]

5w40? Yikes. You don't have the film strength necessary for the motor. The oiling system of the 944 (every pre-996/986 Porsche motor) is throwing crap at the wall and seeing what sticks, especially in a 16 valve. If you don't have adequate (high film strength) oil the camshafts will start failing almost immediately (on the lobes, and sprockets, especially on a 968 due to variocam stress). You can have all the ZDDP you want, but inadequate film strength means it was all for nothing.
And there is no spec sheet on their website?

Thanks for the concern. Oil analysis is real, and it will tell you without question if there is bearing or any other wear going on.
also, a quality 5W-40 with adequate levels of ZDDP AND Molybdenum are perfectly adequate for an Alusil engine in a moderate climate. Especially so when the engine is not operated in winter.