early/late main bearing differences

[jcaster]

This is urgent since I have the engine ready to reassemble on a 1984 944. I ordered part # 944-101-901-00 main bearing set

944-101-901-00-M41

Main Engine Bearing Set, Standard Size, 944 (1983-05/85), Each

It appears that 3 of the bearings are different from the ones that I pulled from the engine. On these 3 one half is the same as the old ones. However, the other half on these three does not have the two oval holes like the old set. One site says these may be ok to use but Pelican support said he was unsure and suspected it wasn't right. Does anyone know if I can use these bearings?

[Smoker324]

Can you post pics? I was under the impression that 2,4 and 5 had smooth bearings for girdle side and grooved/slotted ones for the upper cc?? Pics will heal clear it up.

[KrazyKarl]

I believe there is a page in the factory manual that mentions an update to the main bearings where only one half has openings instead of both. I'm afraid I don't have my copy handy at the moment so I can't be sure.

EDIT: Turns out I did have a copy. On page 13-20a it states on the update bearings that on #1 "The closed main bearing sleeve for bearing #1 now only has a lubricating groove around one half" For 2, 4 and 5 "The bottom halves of the bearing grooves are designed without lubricating grooves. When installing it is important, the bearing shells with lubricating grooves are placed in the upper crankcase section and bearing shells without lubricating grooves in the lower crankcase section." And finally it states "these bearing shells may also be used in engines before 1985/2 models."

Long story short, you can use the bearings you were shipped.

[Smoker324]

Can you post pics? I was under the impression that 2,4 and 5 had smooth bearings for girdle side and grooved/slotted ones for the upper cc?? Pics will heal clear it up.

[jcaster]

I was indeed given the information that these were updated bearings by a parts guy at another shop after Pelican was unable to verify this. I did install them with the smooth side on the girdle side and the slotted side in the upper crankcase. Smoker, the old bearings apparently had slots on both upper/lower bearing halves on early models and these have been superseded by the smooth lower piece for improved oil pressure. I do not have pics but the new set looked like this:
Porsche 944 Main Bearings - DriveWire.com

Now another question: When I reinstalled the girdle I put loctite 574 on the left side around the oil gallery as the haynes manual stated. I am now concerned that perhaps I should have put loctite 574 around the entire mating surface of girdle/crankcase. So is it ok to just seal around the gallery area?

Thanks again.
Josh

[KrazyKarl]

Factory manual says "Coat lower crankcase section with Loctite 574 in areas of oil intake and sealing surfaces in areas of flywheel." I'd imagine if loctite 574 was required around the entire mating surface of the girdle the factory manual would state that in its instructions. That being said, I'm in the middle of rebuilding my S2 engine and when I get to the point of securing the girdle I'm leaning towards coating the entire mating surface of the girdle with loctite.

[HondaDustR]

The new bearings will work fine and are probably better since the load bearing bottom halves have more surface area. An american V8 blueprinting book brought this issue up as far as trying to prevent spun bearings by increasing oil delivery, and fully slotted bearings were one option, although the load bearing capabilities decrease significantly when the bottom halfs are slotted. Keep in mind the crank gets the oil pressure to feed the rod bearings only when the oil hole in the main journals line up with the slots in the main bearings. The fully slotted shells will provide full time oiling to the rods at the expense of main bearing life. Absolutely make sure you get the slotted halves in the block and the smooth halves in the girdle! I knew that and was thinking about it during the whole rebuild trying not to forget and yet the slotted halves still wound up in the girdle somehow. Luckily I caught it before stuff started to actually go together.

The girdle needs loctite 574 only around the oil pickup channel, but also on both sides of the RMS area. If you look at it, there's about an inch of metal to metal seam between the RMS and where the oil pan gasket starts sealing to the block. Seal the girdle so oil can't leak there or past the outside of the RMS right where the two parts join. Work fairly quickly (initial torque stage completed and all bolts installed no longer than ~10 minutes, the shorter the better), since it does start setting on the metal surfaces right away and even faster once their mated. I had gotten the oil pump mounted on mine and needed to remove it 20 minutes later and the sealant was all solid and needed to be scraped off with a blade.