Main bearings

Is the eng out on a stand or are you up under it under the car? (I'm assuming under the car). Unlike rod bolts (cause they locate the cap) you can replace main bolts WO align bore or honing if that ends up being our solution). W this happening so soon can you post some clear close up pics of what we're dealing w? EDIT What eng

It's normal for bearings to lose the satin new finish and turn shiny after use.

The engine is on a stand. Theres 2feet of snow so i got the time. I`m about to do some porting to the heads so i figured i could check things so everything would be ready for summer. I lost bearings last summer,after rebuild, i think because main bolts came loose.(???) I had the crank turned and everything seemed ok. After the runs oil pressure dropped some, from 70 to 45 psi, with 20/50 valvoline racing. so something happened? I
`m gonna tear it down and check the rod bearings also. What else? I`ll try to get some pics for ya tomorrow.

Ok. Here`s a pic of the bearings. They are the three middle ones. Now that i looked at them with better time, i think they look ok. I just got paranoid after last summers problems. The engine is a 360 with 12-1 icon forged pistons and scat I-beam rods, a Lunati ft-cam, and w2-heads. But the oil pressure still bothers me.

If the crank passes the fingernail test, just clean it all out, and if you want, throw a hundred dollars in replacement main bearings at it.

Thanks. I`m starting to feel the same way. The crank looks good (and feels) so i think i`m good to go.

Actually, have to admit i didn`t measure after the last trip to crank grinder. Anyway, The oil pressure was good after i put it together (70+ psi) but dropped after the trip to the strip. If all bearings check out, could it be the oil pickup tube which i found at teardown to be a bit loose at the pump end threads, and suck air threw the threads? What do you guys use for sealant at the threads if any? i thought of a tack weld to lock it to the pump but that won`t seal it all the way.

can you catch a fingernail in those marks on the bearings ? measure the crank and install the bearings and measure them in their respective main bors to find your clearance. Yes you want to put a pipe thread sealer on the threads, but the pickup should not be loose in the threads either .

Actually those marks on bearings are the original satin finish. The picture doesn`t show it very good. The pick up tube was tight when installed and i was afraid to turn it a whole turn more to get it positioned correctly. I was a bit surprised it was loose, but live and learn. Will plastigage give me a accurate enough measure of the clearances? I`ve heard some like it and others don`t. I used it the first time and should have some left in the shop.

I am going out on a limb & say that the clearance was way too tight (& maybe the psi dropped when they wiped shiney & clearance increased it). Since the crank looks good I'd get some .001" under bearings or some same size bearings w increased clearance. . No way should they be wiped that shiney in that (brief) amt of use. Sumpin ain't kosher. NPT threads need sealant & w yours being a bit loose use the thickest sealer you can find. Permatex #2 in the toothpaste like tube is good.

Thanks. I`ll do the measuring. I think its the only way to get piece of mind. I´ll be back when i get some numbers so we can see if you hit it correctly. Is there a way to check the oilpump itself before installation?

Does your 360 have a 90* oil filter adapter? If it does, do you have the proper gasket between it and the block? If not, you will be bypassing the oil filter and will tear up the bearings like your photo shows. Your pressure will still be good but the filtration won't be there. Don't ask me how I know.

No, I have the filter straight. I,ve been using fram filters(ph 43), but been hearing they wouldn`t be that good. Would there be any benefits of using the 90` and being able to use longer filter?

This was hot engine vs hot. Got me some plastigage and got to measure a few journals. The middle one showed 002 and the front one less than that. So i think clearances have been tight. I think it should be more like 0025 with new bearings. Will see what i find at the rod journals. I asked at the speed shop for 001 under bearings, but he didn`t have any listed on the 0.02 under size. Are there any available or is a trip to the crank grinder my only option to gain more clearance?
I also bought ARP main bolts, but they don`t have the provision for a windage tray. What`s my options on that one?
And thanks for the help. I really appreciate it!

Got the rod journals measured. 0.oo15. bearings looked pretty good. Is this too tight?

yes too tight. the most critical area (in the oiling system) is providing for the rod journals/bearings. Check w your crank grinder but might not be able to get the clearance you need by polishing. It'll make it out of round. Polishing is more for achieving a smooth finish. Keep searching for the correct oversize bearings you need. Peruse the SB "parts for sale" for a set of the shouldered 4 main bolts you need for the tray and do not use the large washers on the large bolts "if included" w them. there's a set (+ the tray) in there a day or 2 ago for $25 & I'm tempted to grab it myself even tho I dont need it (at the moment) cause the price is right and someday I will! Use flat washers or flat spacers between the tray and the large bolt shoulder to adj the tray height. Also check that the main bolts are not bottoming out

I `ll give a call to our local parts supplier. They will know if such bearings are available. otherwise, it`s a trip to crankgrinder once again... Thanks everyone for the help!

Let us know how it turns out

There is not such bearings available in that undersize. (.02+001). But the speedshop guy is also a known enginebuilder and he felt that i should be fine with clearances i have. But if i wanted more clearance i could take some from the backside of the bearings with a 400 grit paper. How does that sound to ya? Could i be ok with what i have?

You would be better off taking the crank back and having it repolished. A good machinist will have no problem taking off a 1/2 thou with a fresh belt.

Ok. So i should be good to go as it is. i`ve heard that from several now. that would be good money wise. Would be so many places to spend that money...

for a daily driver .0015 would not be too tight but for a 1/4 miler I would definitely want more but I dont want to cause you undue worry & good luck & stay in touch w us.

maybe I'm getting too old or loosing it but I always thought if you want more clearance on a bearing you would go 1-2 thou. over size.
If you cut a crank 10 thou. under standard size then you would install a 10 thou. under bearing .......forgetting clearence for the moment.
If your crank is standard and you need more clearence wouldn't you have to install an over(standard size) bearing to give you the desired clearence.
Maybe our termology is different here in Canada.

A good rule of thumb is .001" of bearing clearance for each inch of crank journal. So .0025"-.0030" on the mains and .0020"-.0022" on the rods. If the engine is going to be run warm quite often, you can go tighter, or just run a HV pump and do a little oil system massaging (smoothing, enlarging passages).
I don't really recommend doing it (though I have in a pinch), but I've used worn out scotch brite (green) on the face of the bearings to gain clearance. Keep clean solvent running on it while you run the SB across the bearing. I hold the bearing half in one hand and scotch brite on my thumb of the other. I cover half the bearing and count the number of strokes. Flip the bearing, do the other half. Then I flip it again and lightly go across the whole bearing face. You won't gain much, but if you're close it will work. And if you go to copper, you've gone too far. Kind of a last ditch effort sort of thing. The best thing to do is take the block to the machine shop and have the main housing bores opened up and the big ends of the rods opened up as well.
As for filters, the PH series fram filters have no place on anything performance. The TG filters are closer to a WIX type filter and I'm not afraid of them as much. Is the plug under the #5 main cap that directs oil to the filter still there? That'll cause low oil pressure.