Hot Rod Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 ·
2 questions:
1: Putting pistons in my Dart 434 and it uses King Rod Bearings. Found that all of the used bearings have the same marking. The bearing is black (original color) but there is a shiny line that I'm guessing is made by the oilier hole in the crank. The bearings are all smooth and appear to have no wear. Will replace them anyway.
2: King also list a narrow bearing. In what case would the narrow bearing be used?
Musical instrument Wood String instrument accessory Composite material Metal
 

·
Race it, Don't rice it!
Joined
·
8,822 Posts
That's not uncommon. The black is just a coating that comes off easily.
Those are not a narrowed bearing, Narrowed bearing will have a 1/8" chamfer on the edge closest to the crank cheek.
Those are looking good and I wouldn't hesitate to reuse as is.
 

·
Race it, Don't rice it!
Joined
·
8,822 Posts
If you looked at the location is likely lines up with the crank oiling hole. IT MAY have had some start up debri go through it but from over here, not enough to worry about and I'd reuse those.
 

·
More for Less Racer
Joined
·
20,943 Posts
I would expect any crank used to build a 434" SBC is going to be a forged aftermarket piece, and as such they nearly all have a larger cheek radius on all journals (because it adds a ton of strength)and would require the use of narrowed bearings.

It looks to me like it has narrowed bearings but they were installed backwards....uppers and lowers swapped.
Note the distance from edge to locating tang in the picture Steve posted.....then look at the mirror impression left by the tang in the other half....the distance is different from that impression to the other bearing edge.

The narrowed side of the bearing should be on the large chamfer side of the rod.
 

·
Registered
Joined
·
15,322 Posts
Johnsongrass1 has this nailed. You’re running a standard 1/16 inch radius journal to cheek merge of a stock Chevy crank to a crank with a 1/8 radius. It peeled a chunk of bearing surface off that gouged the bearing inboard. You need to see how much scratch that put in the journal. That might require polishing if not turning to an undersized to get a clean surface.

The simple answer is to run a narrowed bearing made for this purpose, the SBC doesn’t seem to have a problem with a narrowed bearing where the FE Ford does big time. So the SBC gets away with the low cost solution of a wider radius cheek to journal where if your shoving the FE you need the considerably more expensive process of a rolled fillet in that corner with the crank cheek which eliminates that radius with an under cut that is pressed into the steel.

Bogie
 

·
Race it, Don't rice it!
Joined
·
8,822 Posts
If your worried, it's perfectly acceptable to chamfer the bearing a bit more with a cheap deburing tool. Assemble the cap-rod with bearings and run this tool around the outside a few times till you get it where you want. Material comes off quick so check after 2-3 rounds.
Noga is a great tool but even $10 dollar ones work too. Just not as nice to hold onto.

 

·
Registered
Joined
·
15,322 Posts
Bolt two rods to the crank and check side clearance. If bearings are too wide you wont have enough clearance between that pair of rods.

Clay
This is not a side clearance issue per se, the problem is factory dimensioned rod bearings are for the factory crankshaft that uses 1/16th inch radius flare between the rod journal and the pin cheek. Aftermarket cranks use a 1/8th inch radius flare which requires a narrowed bearing insert to prevent binding on this larger radius. As Johnsongrass1 points out you can angle trim the a standard bering to fit but of course you would need to recognize the difference before assembly.

This does not affect the side clearance if you stick a feeler gauge in there it will appear with the correct clearance. Actually the rods are being pinched together. What you would see is no lateral movement of the rods. But who looks for this? The problem is as the rod bolts were tightened the wider bearing gets bound against the larger radius. You should feel this when rotating the crank but given a fresh build is pretty tight it’s understandable that it can be missed.

Bogie
 
1 - 13 of 13 Posts
Top