Main Bearings

[hotrodcbx]

I have a 296" blown flathead which has run great for 25000 miles over 6 years. I have dropped the oil pan to check the bearing condition and although they look good I want to replace the mains. It appears they are standard as there is no .010, 020 etc stamped, which I find hard to believe as the con rods are .020 over..I believe they are Federal Mogel as there is a square box on the bearing with FM in it. The part number is 9801-sb with a "LX" under it. I have been on the FM website but this number does not exist..Any information would be greatly appreciated....Thanks...Doug

[Cecil/WV]

I wouldn't trust that they are standard. I would have to mike them to be sure.

[hotrodcbx]

Found out on the HAMB website that the SB after the part number is for "standard bearing".. Don,t know why it didn,t show up on the Federal Mogel website.. Do any of the Barners have a preference manufacturer??? Feder Mogel, Clevitte etc...Thanks

[GOSFAST]

You really need to measure the crank, and I would recommend the Clevite brgs, doubt you will find any more F.M. anyway!

Thanks, Gary in N.Y.

P.S. The "SB" on the brgs denotes the material in the brg, it means "steel-backed" & babbitt lined, not the size!

[richard crow]

if the shaft is in the car it is hard to mike it . you might be able to use a calaper. you can also mike the shell & then mike a known std shell & you will get your answer .of corse if the shaft is out it is ez to mike the shaft. if the bearings look good plasiic gauge them. if clearence is with in spect. button it up .if you drove it 25,000 in six years thats less then a 1,000 a year. the bearings schould be good for an other 6 years.

[Russ/40]

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Originally Posted by richard crow

if you drove it 25,000 in six years thats less then a 1,000 a year. .

Interesting math? ??

[Walt Dupont--Me.]

Std. main bearing thickness .0855 The easiest way to mic a bearing is to take something round like a flathead piston wrist pin .750 stand it on the bench, lay the bearing against the pin, take a 1in. mic and mic the pin and the bearing together. std should mic .8355 If the bearing is .010 or .020 ect each bearing half is half that size. SO, say the bearing is .010, each bra will be .005 thicker than std. So with the pin it should be .8405 Is that clear as mud. Walt

[richard crow]

ment to hit the 5 key walt dupont--main explaned it very well follow his inst.

[Rich Overton]

Originally Posted by hotrodcbx

I have a 296" blown flathead which has run great for 25000 miles over 6 years. I have dropped the oil pan to check the bearing condition and although they look good I want to replace the mains. It appears they are standard as there is no .010, 020 etc stamped, which I find hard to believe as the con rods are .020 over..I believe they are Federal Mogel as there is a square box on the bearing with FM in it. The part number is 9801-sb with a "LX" under it. I have been on the FM website but this number does not exist..Any information would be greatly appreciated....Thanks...Doug

The 9801 is a number stamped or printed in black ink on the back side of the shell. The odd number designates that it is part of a main set. The full set number could be , for instance set #9800-M. The SB designates the bearing as a "steeled backed" with a babbit overlay. Ap would be aluminum, cp copper backed, Ca copper alloy etc. Federal Mogul Purchased Clevite from TRW in the '80's. The difference between Federal mogul engine bearings had been that F.M process of plating was to layer the plating such as copper evenly spread in powder form over the shell. then the Steel backing was flash heated melting the copper creating an equal amount of plating over the shell. Clevite's process was to use molten material such as copper applied directly on the shell. during micropic examination, it was found that the Clevites would have heavy and light coatings on the bearing surface. Both processes proved to be equally good.
As far as f.M being still available, they still have numerous salespeople on the road. Here is a contact for you, Joe Jagielski, of F.M. Joe lives in Sewell, N.J. He has been with f.M. for at least 30-35 years since back when F.M. Engine bearings was our lead line of all of f.M.'s offerings. If Joe can't answer your questions he will direct you to someone who can. ph-609-238-8339, [email protected] Good Luck.

RichO.

[ford3]

measure bearing thickness, then get a depth gage and measure from the block to the top of the main, now subtract the thickmess of the bearing you should come up with the the size of the main

[ford3]

also on the subject of crank sizes, mains wear very little, so some one may have just lost one throw on the crank, and it had ground to that size just to clean it up, the mains may have been fine so they were probably just polished and left standard, ive taken apart v/8s with differt size throws, maybe one throw was just ground and the rest left as they were, alot of strange things have happened to these engines when money was tight over the 60 years or so, i have also found engines with different size pistons in them. one or two bigger than the rest, anything to get the car running when monet was scarce

[Flathead]

Some may be from "fly by night" rebuilders too.