I've been building and racing Mopar since the early 1970s, one of my first problems on B R/B motors was a 1973 CA Highway patrol 440 motor out of a junkyard in Barstow, CA that a customer bought and brought to me to build it to replace the motor he had blown up in his 1971 Charger R/T 440 six pack car. I sent that block to the machine shop I used in Orange., CA to have it hot tank, magnaflux for cracks and the usual machine work needed to reuse some of his parts along with new cam bearings and freeze plugs.
I assemble the motor and the cam shaft didn't slide right in, it turn hard but I was stupid enough to think it world "breakin" WRONG
It ended up spinning the #4 cam bearing in the block which resulted with me having to fix it for no charge.
I took the block to the machine shop and told him about the cam not spinning easy and he told me that was not uncommon on Mopar B and RB motors I had him install new cam bearings and fix the fit with the cam to those new bearings, which he did a good job on I ask him about align honing the cam tunnels and he told me he couldn't do that with his Sunnen CK10 block honing machine due to Mopar having five different I.D. on the cam tunnel for the cam bearing to fit into
He said he had used small engine hand held hones on some Mopar blocks to get the I.D the proper size but it might be better for me to use a bearing knife to make the cam fit the bearings after they where installed instead of having him do it. He was always busy , like most good shops where and he was 100 miles away also
I bought the tool needed to install cam bearings after that along with a good bearing knife so I could scrap and fit the bearings to the cam if needed. I have since seen about a 5 to 20% of the blocks needing the bearings fitted to the cams
It is really to bad Ma Mopar didn't have a higher standard on that step in the block preparations
End of rant, take nothing for granite
I forgot to mention that I had spent the better part of last Tuesday scraping the cam bearings in a 1972 440 block I'm building now

Cab my old machinist, Henry Simon, ( he's the guy that line honed and bushed the lifter bores in the Moparts engine masters entry years ago). Told me the same thing that the Mopar bb motors had terrible bearing alignment issues with the cam bearing bores. He would alignhone them and us locktite to keep the bearings from moving He showed me a motor he had done it on, the cam turned like it was on needlebearings

I was told the same thing back in the '80s.

Cab, I feel much better now. That was my SECOND big mopar lesson I learned. My 340 warranty motor in my AAR had the same problem. I took it to the wrong machine shop on advice from my old SS engine builder. This was before he opened up a full shop. I started the cam in with a hammer! It would not turn at all, fortunately. Lol! I took it back and they fixed it. My oem cam would fit but not the new one would. I was told back then it was simple core shift from all the heating and cooling cycles. My first mistake was the old pilot hole in the crankshaft was too small because I had an automatic crank. I just drove in the bronze bushing and shrunk the id. Like to have never figured that one out.

Yes, if you build any mopar engines, sometimes you have to hone or scrape the cam bearing bores. I use a dowel with a slot cut into it chucked into a drill. I fold some 320 sandpaper into the slot and turn drill at low speed. I usually tap the cam into the block lightly and get some markings so I know which bearings need attention. I have never done it, but some guys will take an old cam and cut a slot on each journal, and then file a relief on one side of the slot, tap in the cam and rotate, it acts like a reamer to scrape the bearings, then you can dress them with sand paper. I then use oily rags on a dowel to make sure I get all the residue from the bearings. Never had any issues with spun cam bearings. You just have to make sure you fit the camshaft as your first step in assembly. The only other thing is make sure when you tighten your cambearing installer on the bearing you get it good and snug, and make sure it stays snug as you drive them. I use a snap-on installer, and it sometimes likes to loosen as you drive the bearings in, if the driver gets loose on the bearings, they will shrink as you drive them in just a little.

I've had a few blocks over the years. Some had problems and some didn't. Its hit and miss. The '76 440 block I have now had no issues and you can spin the cam by the pin on the front.

there was a mention (on here) of notching the journals in a used cam with a hacksaw blade & useing it as a reamer

Different size bearing bores isn't just a Chrysler thing. BBC mark 4's are different too. Dart big m's come with a tech sheet that shows cam bearings to be standard BBC however they have all the bearing bores at 2.120, and there is a special number for those. My little rant. Most cam bearing tools you drive in with a hammer. Sometimes you will leave them a little funny hence the reaming/scraping begins. I have an older OTC tool that draws the bearings in with a bearing and a threaded nut. Once I learned the proper amount of Jiggle between the collet and bearing shell before installation things go much better now.

Rick Ehrenberg has discussed this many times, according to him the factory align bored the cam bearings.

I don’t know where I heard it...... and I have no way of knowing if it’s true or not, but I have seen enough weird stuff with factory Mopar cam tunnels that I believe it’s true.

My understanding is the bearings were sized in place, with a long 5 step reamer type of tool...... where all 5 bearings are cut at the same time.

I always figured was a cost savings of some kind.
Somehow maybe cheaper to make it work at the end of the line rather than from the get go.

I haven't built that many compared to the pros, but I have never seen a cam fit correctly on new bearings.
All that I have done were too tight and I had to monkey with them.

Bearing scraper and scotchbrite pads for me.

This is fact. Up until I left the engine group the Trenton engine plant installed “green” cam bearings then machined them all at one time.
Green means “not finished to final size”.

The Kokomo Trans Plant did the same thing with all auto transmissions. Pump/converter bushing all the way back to the output shaft bushing and everything in between.

Were the cam bearings “bored” in place one at a time, or was the process more like one long tool with 5 different sizes, and all 5 bearings cut simultaneously?

Here ya go ...

I actually never saw the tooling or it being used but during a deep dive on some broken cam warranty issues the subject came up of bearing wear. In every example of a broken cam we saw the center two bearings heavily worn on the bottom. It was mentioned then of the process and tooling, one station to cut the bearings. As it turned out the cam installation station scratched the cam journals and those scratches wore the center two bearing bottoms causing the cam to be unsupported in the center. Every cam broke almost in the same spot.
This was on the FWD 3.3/3.8 engines. I was told this process was adapted from the B/RB process of the late 50’s.

I use that Harbor freight Tool on my crankshaft scrapers for the five large oil drain back holes at the main webbing

I have always used an old cam with slots cut in it to relieve the offending bearings. The dress the bearing as needed and been good to go with no issues.

Me too.

Almost the same end result as what the plant did.

Looks like someone has been digging around in my shop. Looks EXACTLY like mine!

Brian