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Clevite "H" Brgs vs. Conn Rod S/Clearance

1318 Views 3 Replies 4 Participants Last post by  Wolfplace
This info pertains to SB's only at this posting.
An issue came up just today involving Clevite "H" series rod bearings and an "Eagle" 4340 aftermarket steel crank with high radii on the rod journals. Upon checking rod side-clearances, directly between the pair of rods we took readings of about .020". However, we noticed the outer edges of the rod cheeks weren't quite contacting the sides of the throws. They would stop about .004" short of touching the crank. We had an issue. What we had basically was an incorrect measurement for rod side clearance. Removed rod caps and realized the bearings were "touching" in the radius in both corners. The bearings (CB663H's) were manufactured in August of 2005. In other words, fairly new pieces. I called Eagle AND Clevite, it appears this time around there's some "genuine" concern on their ends. We grabbed a set of bearings manufactured back in 1998, same part number, and rechecked it all. Problem fixed! Somewhere along the line Clevite managed to "lose" a small portion of the "chamfer" from the earlier pieces. We do understand the radius on the throws have a large effect here, but being the earlier bearings corrected the problem, we'll go with it being a Clevite issue for the moment. I'm waiting to hear back from Jeff at Clevite. To sum it all up, we don't see it causing an entire failure, but it won't do the bearings any good overall, and CAN be corrected even at final ass'y. To do a "QUICK-CHECK" follow this procedure: Take a pair of rods on each journal, have them torqued, and carefully place a feeler guage or small strip of newspaper (.003"), one side at a time, between the cheek and the side of the rod throw and it should "clamp" the paper there. If it doesn't, the bearing is binding. Whatever you do, DON'T assume because you have enough room BETWEEN the pair that your safe. It has to be checked on both sides and the center. This entire procedure can easily be missed on both pre-assembly AND final. We almost didn't catch this one ourselves. Thanks, Gary in N.Y.
P.S. You can actually grab the rods and "snap" them front to rear and get a distinct "metallic" sound as long as you don't have lubricant on the cheeks. If you don't get that sound, stop and check further. We don't put oil on the rod cheeks on ass'y, we simply lube the inserts. The cheeks get oiled when priming the short block. Some of you guys using Scat parts may want to look closely in the same areas. Sorry for the length!
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Good post Gary,
Its really getting discouraging how much you have to check everything now days. Seems like none of the manufacturers are immune. I have seen some bearings where the "tang" is actually not in the correct place, causing the same problem. Also lately have seen quite a few aftermarket rods where the locating slot is not quite big enough and the bearing does not sit flat against the rod bore :( You absolutely have to look at and check EVERYTHING.
So ... you want to build performance engines :clonk:
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