Are the main bearings different on a mega block vs a standard 440 block? I ordered main bearings for a 440 and I cannot get the thrust bearing in either the block or the cap….help…

Mega blocks should be machined for the larger thrust bearings so either style should work, but that is the first thing to check. Is this a new block? Did you have a machine shop check the main line and fit the bearings for you?

Just left the machine shop and what has apparently happened was something I had never heard of…the early model blocks have room for a wider flange and later model blocks have a narrow flange, I do not know what year this block is, it has pn 2468330-M on it but no date. The machine shop traded me some King bearings with a narrower flange and they fit perfect but the are 1/2 grove vs full grove…should I be concerned? This is a 1000 hp bracket engine, thanks.

I run the King bearings in my Megablock 528 Hemi for several seasons now on the street and strip use with no issues.

[quote=6PKRTSE]I run the King bearings in my Megablock 528 Hemi for several seasons now on the street and strip use with no issues. [/quote
Are they full or half grooved?

I will have to look at my records for the part number, but they are the XP series. Half grooved. I believe they are REBMB5116XP. I have always preferred King over Clevites, Fed Mog or others quality over the last several years. We build hundreds of engines every year with both King and Clevite bearings.

Thanks for the update, looks like I’m going to have to polish the crank or order some .002 under size bearings, my clearance come out to be .001 to .0015…uggghhh

Get a set of 3/4 groove bearings if you can. Bearings can be a real pain these days to source and sometimes the quality is poor when you do get them. There aren't a lot of choices for BB Mopar engines although the RB does have more choices than the B blocks.

Mahle/Clevite did some testing on the oil grooves and found the half groove oiled better than the full groove. It's in the performance bearing catalog.

"While a slightly shorter groove of 140 degrees
provides a marginal gain, most of the benefit
is to the upper shell, which doesn’t need
improvement. On the other hand, extending
the groove into the lower half, even as little as
20 degrees at each parting line (220 degrees
in total), takes away from upper bearing
performance without providing any benefit to
the lower half. It’s also interesting to note that as
groove length increases so do horsepower loss
and peak oil film pressure which is transmitted
directly to the bearing."

Thanks for everyone’s help and feed back, I’ll be digging through this in the morning and making some phone calls, this is the second set of King bearings I’ve run across that tightened up the clearances…we measured the crank journals and the line bore and they are both dead on

Mine runs the 1/2 groove Clevites with no issue. If the crank measures standard, there should be no way a performance bearing mesures that tight. I can't say for Kings, but Clevites will usually give about .0027-.0030 depending on line bore dimension. The line bore of your block may be to tight. There are no .002" bearings available that I know of. I would not run under .0027 on the mains.
Doug

There is no way in the world that I would run 1/2 or 3/4 groove main bearings in a 1000 HP drag motor, NO WAY
As far as what is supposedly written by a manufacturer about testing, maybe they don't want to make those bearings anymore due to the low volume we Mopar racers buy
I've put a lot of motors together, some of all brands, one Ford FE motor I refresh for a friend who loved and only owned and drove Fords had a Holman and Moody 427 side oiler motor that used a full groove on all the main journals on the crankshaft for oiling the rods full time, it also had cross drilled oil passage on all the mains also

I agree. This all might be true about the upper and lower halves of the main bearing, but the advantage of the full grove is in the feeding of the rod bearing which is the more severe of the two applications.

Well, after two trips to the machine shop, numerous phone calls and hours spent remeasuring everything it looks like the line bore was off about .001 to .0015 so back to the line bore machine it goes, isn’t this fun…, tried to find some “X” bearings but apparently then are made of unobtainatainum right now so here we go….

Not a surprise. Engine building is harder now than ever. Almost everyone is making junk these days. The good stuff is all on back order and sometimes it is damaged when you do get it. It is almost impossible to find main bearings that are any good now. Sometimes have to buy two or three sets to make one good set.

Try and have them align hone the main bores, not align bore them

I don't agree. Clevite knows more about bearings than either of us. Though mine doesn't make 1000 hp, I'll bet it makes north of 900. Been running for 11 years, nearly 1000 passes. Regularly sees 7100-7200 with a 4.5 stroke. 3/4 groove have never been an issue.
Doug

Same here with mine. No issues. Plenty of street miles also.

I like and use the Clevite full narrow groove truck main bearings
Works good, last a long time
Did I mention that Murphy loves messing with me