Have a set of small journal rods with the spit holes in front of me.. There are many different 3 numbered rods in the set of 8... Is there any reason for the different GM numbers and what the heck do they mean.. Have large dome pistons hung on them.. Gonna measure them later as I do not see any numbers on the heads of the pistons denoting oversize..
Thanks!!
T.

... many different 3 numbered rods in the set of 8... Is there any reason for the different GM numbers and what the heck do they mean.. Have large dome pistons hung on them.. Gonna measure them later as I do not see any numbers on the heads of the pistons denoting oversize..
Thanks!!
T.


It is very common when doing a rebuild and running into a rod that requires excess work or machining (due to bearing failure or ??? ) to just reach into your spares and get another one for the rebuild ;)
Original GM rods were all of a fairly common forged design and plenty strong for most engine builds - unless you were going for 'big' HP numbers or building an endurance enegine. So it was quite common to have rods from several different casting lots in them and thus several differnt numbers on the individual rods. Specially in the earlier days when all Small Blocks used the same 5.7" length rod (no 5.565" '400' rods yet) and aftermarket rods were more of a specialty item.
As long as the rods were sized right and the bolts were replaced or upgraded in size almost all the production rods were "good-to-go" in most street performance engines.

I still have a bucket of stock rods in my shop from older engines as spares - don't use them much anymore as aftermarket sets are so cheap :yes:

A quick measurement of the piston size will tell you if it's standard or an over-bore :thumbsup:

Thanks Vintage 68 for the explanation..
T.

If they're not the '66-up SJ rods with the added meat adjacent to the bolt head seat, I wouldn't use them for any performance application.

Ditto what John says. The only SJ rod I'd even consider for a build would be 66-7 and probably narrow it down further to 67 only since they stopped putting the spit hole in the caps in 67 because they aren't needed. I'd also run ARP Pro-series wav-loc bolts in them.