Did I get the wrong bearings? 2.5 Iron Duke / 1985 (Page 1/1)
82-T/A [At Work] MAR 17, 04:51 PM
So, my daughter put together the bottom end of the engine today... assembled the rings (she'd actually done that a week earlier), and we installed the main bearings, installed the crank, installed the main bearing caps, and installed all the pistons facing the right way with the rings all properly spaced etc... and torqued everything down to spec per the service manual.

The ONLY thing that made me somewhat uncomfortable, were the Mahle / Clevite main bearings. The set we ordered was Mahle/Clevite MS-1733P. We got them from Rock Auto, and they're advertised everywhere and the 1985 Fiero 2m4 Iron Duke is one of the engines listed as being compatible... which is why I ordered them. They show them as good for all 5 years of the Fiero. Anyway, the issue I'm concerned with is that the large circle opening for the oil passage did NOT properly line up with the hole on the bearings. I'm attaching a picture below of the bearing set (basically exactly what I have):




As you can see in the image, I put a red circle where the oil passage hole in the block lined up with the bearing. Make no mistake, oil absolutely can get into this passage and will spread around, etc. The hole from the engine block lines up properly with this long "open" slit that goes down the center of the bearing surface. But just eye-balling it, it seems like only 80% of the oil will properly flow through there. The other two large holes you see in the bearing... they don't line up with anything on the engine. It makes me think that they've designed this bearing set to basically work with several different kinds of engines.

Am I OK?

Note, when I look up other sets of bearings on Rock Auto (cheaper ones), the holes in the bearing surface are actually smaller than the holes that I'd get from the Clevite bearings...which makes me think this is all totally intentional.

Thoughts?

(here's an image of a shitty set of Engine Tech bearings. Note how small the hole in the upper bearing is, which effectively is actually smaller, if not almost the same size as the Clevite that I installed)




Thanks guys... comparing to the ones online... I think I'm actually "OK" ... but just want to know what you guys think...

[This message has been edited by 82-T/A [At Work] (edited 03-17-2024).]

Patrick MAR 17, 04:59 PM

quote
Originally posted by 82-T/A [At Work]:

Make no mistake, oil absolutely can get into this passage and will spread around, etc. The hole from the engine block lines up properly with this long "open" slit that goes down the center of the bearing surface.



Maybe I'm missing something here... but with the "slit" being on the crank side of the bearing, and the oil supply being on the block side of the bearing, how does the oil get to the "slit" if the holes don't line up?

[EDIT 1] Am I wrong to assume the main bearing oil supply comes from the block... and perhaps not through the crank? I admit to not knowing how the oil circulates through a duke. I've never had one apart.

[EDIT 2] After watching a couple of videos, it appears to me that the main bearings are indeed supplied oil from passages in the block, and then the oil continues through passages in the crank to supply oil to the connecting rods.

It seems then that it's imperative for those holes to line up on the main bearings... unless like I said, I'm missing something here.

[This message has been edited by Patrick (edited 03-17-2024).]

82-T/A [At Work] MAR 17, 06:14 PM

quote
Originally posted by Patrick:

Maybe I'm missing something here... but with the "slit" being on the crank side of the bearing, and the oil supply being on the block side of the bearing, how does the oil get to the "slit" if the holes don't line up?

[EDIT 1] Am I wrong to assume the main bearing oil supply comes from the block... and perhaps not through the crank? I admit to not knowing how the oil circulates through a duke. I've never had one apart.

[EDIT 2] After watching a couple of videos, it appears to me that the main bearings are indeed supplied oil from passages in the block, and then the oil continues through passages in the crank to supply oil to the connecting rods.

It seems then that it's imperative for those holes to line up on the main bearings... unless like I said, I'm missing something here.




Oil is supplied from the block. The holes in the block line up with the slit in the bearing. I tried to copy the picture that shows it, but the bearing surface has a large slit (literally an opening) a full inch across the bearing surface, and the hole on the block does in fact line up with the opening in the slit. The size of the slit is actually the same size as the opening on all the other cheaper crank bearings that I saw on Rock Auto (as you see in the image I linked to).


It's probably hard to see in the picture I included. But the four bearings (which are the "upper bearings," the ones that go against the block side), you see a groove, and two large holes. The second hole (the one further down the bottom in the picture), that groove becomes an actual slit / opening for about an inch before it turns into a groove again. Does that make sense? Oil is leaving the block through a hole, and getting into the bearing channel. The question I had is whether or not it's acceptable for the hole to be the size that it is. BUT... after looking at the other cheaper bearings being offered, I realized the hole in the other bearings is the same, if not actually a little bit smaller than the opening provided by the slit on the bearings.

I don't really know what Clevite/Mahle was doing here... but possibly making it so that these bearings could be used in as many engines as possible. But just looking for someone else who's used these and had no issues...
82-T/A [At Work] MAR 17, 06:23 PM
Ok, I found two Reddit threads with the same issue... one is also for an Iron Duke (Mercruiser) and the other is for a Straight-6 250 Ford.

Here are two comments that put me a bit more at ease:

1 - I have 2 different part numbers for that main bearing. The earlier number, Federal Mogul 4123M, has a slot through the groove that intersects the oil hole as yours does in the picture, and doesn't have an enlarged hole offset from the block hole like in your picture. The later number, Federal Mogul 6689M or Clevite MS1733P, is exactly like your picture. I suspect the later number is for the newer versions of the 2.5 liter 4 cylinder, and requires the oil holes as you see them. But the earlier 3 liter can use the later bearing because the slot feeds that hole in the block adequately.

2 - That is a rebuilders bearing. It is fine for a stock/moderate performance build. Install as is.


So bottom line, the bearings are designed to fit a couple of different engines, and it's perfectly OK. This is an Iron Duke, and will never see high RPMs, so I'm not concerned. They're quality bearings... Clevite / Mahle has some fancy words to put behind it...

"Clevite P-Series main bearings are the oldest members of the Clevite 77 bearing family and are intended for high-revving engines. To compensate for the high-load factors and distortion in these engines, these bearings have higher eccentricity and a high crush factor. P-Series bearings are constructed of tri-metal cast copper lead. They have a steel back for support, a cast copper lead lining to withstand the loads of engine operation, and an electroplated babbit overlay on the running surface to provide searing surface qualities. In addition, the oil grooves on most applications extend all the way around both halves for better oiling."
Patrick MAR 17, 06:33 PM

quote
Originally posted by 82-T/A [At Work]:

This is an Iron Duke, and will never see high RPMs...



I just didn't want to see it become a giant paperweight. Sounds like it'll be okay.
82-T/A [At Work] MAR 17, 06:35 PM

quote
Originally posted by Patrick:

I just didn't want to see it become a giant paperweight. Sounds like it'll be okay.




Yeah, me either... I was looking at that, and telling my daughter... "You may be doing this again..." and she was like... well, I want to do it right.

But it looks like it's all OK. She's done more than I have now... I've never done this before.

I will tell you though... it's so important to have good tools. I bought a ring compressor set which came with a few tools... and on three of the pistons, the rings popped out while we were hammering them in the bore. Such crap. She was really frustrated, but we made it work.