Main/Connecting rod bearings

[KonaJet74]

Hey guys,
I just pulled my 454 apart & I'm trying
to ID the bearings. The mains have GM A-200
.0006 stamped on them & the Conn Rods have
GMM400 2621304 stamped on them. Are these
Federal Mogul or stock or???? the crank's a
71' ls6 7416. Thanks......

[SmokinLowriderSS]

Those are likely GM orriginal, although the likelihood is pretty high that FM may have made them for GM.

[Fiat48]

Those are Moraine bearings....gm originals. Special factory sizes to correct the clearances. Not available over the counter.
The .0006 means a bearing different from standard size by that much. Probably .0006 more clearance for that bearing. This is typical of the LS6's and my thoughts are it is done more for the crooked line boring from the factory than for anything else.

[shaun]

Fiat, Funny how you where just telling me this over pm last week and here's a real life example. Just curious, whats his options, will a line bore correct the issue with needing odd sized bearings?

[Fiat48]

Yes...a line hone or a line bore will solve the problem if it is done right. But just because it has the fitted bearings done not mean it HAS to be line honed. Best bet is to check the block sizes and straightness.

[KonaJet74]

I pulled the motor because it's been sitting for a
good number of years, but the bearings look new
and are perfect. It's definately a Ls6 motor from
checking the ID #'s on the block,crank & heads.
So, if everything checks good I'll put it back
together. Do you guys have any recomendations
for a Roller cam upgrade & what works good with
these 454's with a Berk JC & "A" impeller?
Thanks guys!!!!

[SmokinLowriderSS]

I dug my Desktop Dyno file for LS-6 up on my laptop and replaced the .500" factory cam with the .565" lift Isky 280H (custom cut from HTP) I am running, and it helped tremendously the enemic lower-end and midrange that the factory solid had. Made a few more HP top end too. I am working with the Iron headed non-vette version here, 10.2:1 One source of mine said 11:1, another said 10.2:1.
Orriginal: Torque HP
2500 277 132
3000 325 186
3500 359 239
4000 385 294
4500 407 349
5000 414 394
5500 404 423
6000 384 439
6500 347 429
7000 294 392
My 280H cam: Torque HP
2500 390 186
3000 427 244
3500 452 301
4000 463 353
4500 464 398
5000 453 431
5500 425 445
6000 383 438
6500 337 418
7000 278 371
445HP @ 5,500 compared to 439 @ 6,0000.
Stock engine should spin an "A" at just short of 5,000 RPM, tight pump, properly fed. 1,000 RPM short of the engine's peak.
Re-cammed one, just short of 5200 RPM, same pump. About 300 RPM short of the peak.
Just an example of what is possible. Those big rectangle-port heads hurt the mid-RPM muscle with the increase in Hi-rev HP..

[KonaJet74]

Thanks for the info! I'm replacing the cam with a
comp roller w/ .547int, .564 exh with 236int &
242exh at .050 on a 108 LSA. I've been talking
with comp & that's what they recommended for
my setup? I wanted a mean sounding cam &
didn't want to kill the bottom/mid power. I
won't be pulling skiiers, just hauling between
bars on the Delta in NorCal. This is my first
jetboat, damn it's going to be a long busy
winter getting it put together! Thanks again!!

[SmokinLowriderSS]

I was amazed myself how little the orriginal motor had for bottom end in stock form. Had to be a dog till you wound the snot out of it between the smalish cam and the big rectangle port heads.
I just finished an "iterator" run on DD looking for max torque, and gave it a range surrounding my Isky cam ... here's the results, just for shi+s and giggles.
Best #1 result:
Hyd cam, lobe center 109*, duration 276* both sides.
Lift .600" Int / .575" exh
RPM Tq Hp
2500 412 196
3000 450 257
3500 469 312
4000 477 363
4500 472 405
5000 454 433
5500 418 438
6000 374 428
Running the exact same iteration setup now for max HP.
I play with this program entirely too much some times. LOL
i'll see what your cam fits in to afterward. :)