Mopar 383 Connecting Rods

[James L Miller]

What brand of connecting rods are guys using in Stock and SS 383 Mopar engines? The only ones currently available that are NHRA legal are the Eagle (at the low end) and Carrillo rods (at the high end). The C-A and the Hale rods seem to be non-existent at this point. My engine guy went through 60 stock rods to find eight that would stay round on the big end.

[Paul Precht]

If you're running stock the stock rods are fine. Unless they're really messed up and been beat to death the only way you'll break one is to spin a bearing and not lift.

[Larry Hill]

James I would like to know the criteria for the rod selection. I have a problem keeping the big end round on my stuff. Fixing them shortens the rods and requires block to be decked to keep compression up.
Thanks

[James L Miller]

Larry, my engine guy is an old tool and die machinist and ran a MP Colt back in the late 1970s and early 1980s. He worked at the Dodge NASCAR engine program with Arrington and Ted Flack when Dodge got back into NASCAR. His rod methodology is to torque the rod bolts, measure the roundness on his Sunnen rod hone dial bore gauge. He redid a set of Manley Hemi Pro I-beam rods that I bought from Mike Bogina. Mike had them on the shelf, brand new in the box. Apparently Manley did not use enough assembly lube when they torqued the rod bolts and there was galling on the threads and under the bolt heads. Robert resized the big ends with new rod bolts, dowels, ground the caps and big end and resized the big ends to under ,0001" (nearly zero). The next day they must have stress relieved to be .0001" out of round.

On the stock rods, he measures the out of round, un-torques the bolts, and retorques them. If they don't repeat they end up in the junk pile. Apparently the stock 383 rods are weak, maybe a low alloy steel or medium carbon steel like AISI 1053. He was building a 383 for a guys pickup and they got a set of Jim Hales (Manley) rods, but they needed work as they were used. Overkill for the pickup build for sure.

[GTX JOHN]

If we resize rods we offset bush the rods small side to keep length.
Nothing wrong with stock rod but by time you rework them they are
about the same money as Eagles

[Dave Noll]

If it was me, for .0001 I'd dig those 60 stock forgings out of that junk pile.

[Paul Precht]

I assume he is checking those rods with the stock bolts. I have at least 10 sets of stock 383 rods laying around, when I get the time I'll try the torquing and retorquing to check how consistent they are.

[James L Miller]

Originally Posted by Dave Noll

If it was me, for .0001 I'd dig those 60 stock forgings out of that junk pile.

Dave, it was my Manley Hemi Pro-I Beam rods that went .0001" out of round after resizing. The big end spec on the Mopar BB rods are 2.5000" to 2.5005" per the Clevite book. I'm assuming that the 383 rods wouldn't repeat within the ,0005" range. I'm sure that was with the stock 383 bolts. I wasn't around when he went through the rod testing on the 383 rods, so I don't know the exact procedure done.

My engine guy also does hardness testing on the rods. I bought a set of Manley 440 Sportsman rods and they were in the HRC 26-29 range. It appears to me that is the normalized hardness for 4340 steel. The hardness on the Hemi I-beams were in the 31.5-39 HRC range (corresponding to 130 ksi to 159ksi yield strength per the EMJ Blue Book charts). Maybe Manley saves money on the Sportsman rods by skipping the heat treatment and final sizing after heat treat steps?

[Larry Hill]

Is your machinist using an AG300 to check size? If so how does he check for straightness of the bore. To check for hourglass or barrel shaped bores.
Thanks

GTX John
How thin, wall thickness, can the pin bore wall be and still live after bushing the pin bore? Does the bushing get burnished or is it a shrink fit?
Thanks

[James L Miller]

Originally Posted by Larry Hill

Is your machinist using an AG300 to check size? If so how does he check for straightness of the bore. To check for hourglass or barrel shaped bores.Thanks

Larry, I don't really know for sure. I saw him put them on the gauge, but I didn't pay attention to the details how he used it close enough. Next time I head to Florida, I'll take my Mitutoyo 2" ring gauge along and have him show me how he does it. Here is a link the Sunnen instructions from the Goodson webpage.

https://cdn.shopify.com/s/files/1/14...cisionGage.pdf