[1_bad_nova73]

hey im building a 383 stroker and i have a set of stock main bearings and rod bearings for a 350 laying around i was just wondering if i could use them on the 383 or will i have to go buy new ones the ones i have are new and have never been used

[68NovaSS]

Depends what sizes they are, what size the crank rod and main journals are and whether they bind against any radius that might be on the rod journal outer edges. If they do, scrape them at an angle.

[GAOldsman]

The 350 main bearings are too small now for the block now that it has been machined to accept the 400 crankshaft. You will need 400 bearings.

[joelster]

Originally Posted by GAOldsman

The 350 main bearings are too small now for the block now that it has been machined to accept the 400 crankshaft. You will need 400 bearings.

If he is using a 400 crank.

Most 383 kits do not need the block machined since they use aftermarket cranks with 350 main sizes.

[GAOldsman]

Correct my friend, I was taking for granted it was a 400 crank. Ooops

[firebird7980]

I thought you turned the 400 crank

[1_bad_nova73]

i didnt buy the whole 383 kit i just got a 383 scat crankshaft from summit so just to be on the safe side just buy new bearings but for a 400 instead of a 350 right.

[68NovaSS]

Chances are a 383 SCAT crank, is already sized for your 350 block, do some research, that should have been noted in the item description from wherever you bought it.

[stich626]

Originally Posted by 68NovaSS

Chances are a 383 SCAT crank, is already sized for your 350 block, do some research, that should have been noted in the item description from wherever you bought it.

x2

the bearing you have. might work, are they standard, 10/20/30/40 ?
google these builds, there are a ton on car craft.com
you need to clearance the block at the oil pan rail.. and at the cyl wall.
and need a small base circle cam.. start reading

[cobalt327]

A SBC '383' crank is going to come (if new) w/standard size 350 mains, so will use standard 350 main bearings.

If the rod and/or main journals were undersize, the undersizes should be stamped into the crank (something like 10-10 or 10-20) . But even w/o any stamps, obviously it's good practice to always mic the journals for diameter and taper- even if brandy new- and check the main journal diameters to the main bearing diameters torqued in the caps. If you don't have the wherewithal to do that, at least use plastigage to verify the clearances. And don't forget to double check the end float- this has caused problems in the past w/some aftermarket cranks of the inexpensive cast versions, especially.

And the advice to check the bearing width to the journal width is critical- some cranks have a large fillet where the crank journal and crank cheek meet and the bearing has to clear the fillet.

FWIW, the only other half-way common '383' SBC is going to be a 0.060" over 400 block w/a 350 stroke crank. This deal will most often use bearing spacers or thick bearings made for using a LJ crank in the 400 block, few places make a 350 stroke crank w/SBC 400 mains.

[PatM]

Regarding the small base circle cam mentioned above. . . . not NECESSARILY required. If you use standard 5.7 inch rods, you may have a problem, but some aftermarket rods are stroker clearanced out of the box. That isn't necessarily a guarantee, but before buying a new cam and assuming a reduced base circle is required, I think it'd be wise to pre-assemble the motor with an old cam. Check that clearance then make the decision.

Pat

[stich626]

Originally Posted by PatM

Regarding the small base circle cam mentioned above. . . . not NECESSARILY required. If you use standard 5.7 inch rods, you may have a problem, but some aftermarket rods are stroker clearanced out of the box. That isn't necessarily a guarantee, but before buying a new cam and assuming a reduced base circle is required, I think it'd be wise to pre-assemble the motor with an old cam. Check that clearance then make the decision.

Pat

true, but I'm gonna go out on a limb, that the scat crank is being used with oem rods, and in a 350 case thats 5.7" rods..

[joelster]

I have a 4" stroke crank in my LT1 which is identical dimension-wise to a sbc. I had a .950" base circle cam in my engine that cleared but was a little tight for comfort. Most 383's do not need a smaller base circle cam.

[stich626]

Originally Posted by joelster

I have a 4" stroke crank in my LT1 which is identical dimension-wise to a sbc. I had a .950" base circle cam in my engine that cleared but was a little tight for comfort. Most 383's do not need a smaller base circle cam.

didn't they raise the cam in the lt1's

[cobalt327]

Prolly thinking about the Gen III engines, they have a raised cam (almost 0.400" higher) compared to a Gen I SBC. But the Gen I and II (LT1/4) are the same AFAIK.