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"The answer is they drove sensibly within the limitations of the technology."

Yes. True. Point well taken. However, there are many here among us that in the year 2009 do not want to become a moving traffic obstacle. Especialy in rural areas where speed limits are 50 mph and faster for stretches of road well over 15 miles long.

As O-D says, there are a number of options. In the case of using latter rods and the now available bearings, that is an excellent opportunity for the 320 owners. Re-babbiting for those who want, and/or have no suitable insert to convert to is also another option. Converting to an insert is very precision work, and requires an understanding of process, materials, and working limits of components involved. I can totally understand why the average mechanic would hesitate to make such a drastic modification.

While everyone searches for the universal proper answer to solving the elusive 320 / 384 rod bearing fix, I will be out driving my fixed car.

However, there are many here among us that in the year 2009 do not want to become a moving traffic obstacle

Eric, if one felt that their brakes, lights, steering, etc. are adequate for a higher average sustained speed, there of course is always the option of a more advantageous ring/pinion set, or an overdrive. That would be my own preference over irreversibly altering my connecting rods.

PS- at the possible risk of running into some copyright problems with CCCA, I'll post one of the better technical reviews of this situation.

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Owen. Many thanks for posting the article. Interesting and very informative/specific.

Wow! Great article...

This is precisely the method I used to perform the conversion on my engine. I will add to this article for anyone interested.

When modifying the slant 6 rod bearing for oiling the wristpin I purchased a slant six rod, mounted the rod cap to a plate and milled a pilot hole for boring each rod bearing to oil the wristpin. As the article says, the slant 6 cam squirt hole will adequately align with the Packard cam squirt hole, but the bearing tangs must be placed opposite of the positioning of the original tangs.

As the article says, the rod must be bored a bit over the original inside diameter (id). The rod is already woefully thin between the bolt bore and id. The bore is broken into just a bit towards the parting line. This necessitates a bit of chamfering to remove flash. This also necessitates a tiny bit of relief of the rod bolt. I worked with an ARP engineer and came up with a rod bolt that is modified to work in the 320 rod. This is a 110,000 PSI bolt. I put the rod bolts in a collate spinner and milled radial relief's at the parting line to ensure no contact between the bearing and the bolt. As the article stated, the stock bolts will take this modification, and the ARP bolts I came up with certainly will without a doubt. The heads of these rod bolts are also machined for best fitment. A huge advantage of these rod bolts is much better alignment of the rod and cap because of an increased alignment shoulder. If anyone would like the special part number for these bolts I can provide it.

As far as widening the rod, it's going to be personal preference. I went full circle on the advice of some sharp individuals, but the author cites brass dots or thread in pins working for him.

I wish this article would have been recommended to me when I (and talented friends who helped) did this a few years ago. I am very happy to see this information available for others to use.

As for spinning the engine harder with inserts, v. babbit or the old style 35 - 39 inserts, I am not advocating this. In fact, I seem to be a bit on the conservative side of how hard to spin one of these engines. As O-D said, gear it taller, overdrive, or live with the mechanical limits of an engine with 5" stroke and 11" long connecting rods.

P.S. I had a nice Sunday drive in my car today. Glad I figured this out, and was able to get it done. Peace of mind, and cheap insurance.

Thanks for the article from the CCCA Bulletin. What was the date of the article? I tried to print it out, but the print comes out too small.

Thanks,

Jim Wayman

Don't know the issue the article appeared in, perhaps 15 years ago, maybe even more.

Try to right-click on the article image, save the images to your hard drive, and then use your print program to enlarge them to full size before printing, or enlarge them with some other program like PhotoShop before printing.