These days, with the modern (crappy) automobile oil formulations, you have to do TWO very important things when breaking in a flat tapped (or THREE if you have stiff valvesprings).
1) run an oil filter WITH NO INTERNAL BYPASS (I prefer Jomar).
2) run a GOOD break in oil (I prefer Gibbs/DRIVEN BR40).
3) If your springs are more than 115 lbs on the seat, then I recommend either running just the outer springs, or your old outer spring - whatever you can find that won't be in coilbind at max lift and is under 100# on the seat.

Prime the oiling with the distributor out, drop in the distrib. Fire it up, watch to make sure youre making good oil pressure, juggle timing to a "good enough" spot. hold it above 2000 rpm for at least 20 minutes. Watch oil pressure, watch coolant temp. If there are oil or coolant leaks, try to ignore them as long as pressures and temps are tolerable. Coolant temp can run pretty warm on this first run.
After 20 mins, vary revs some, but stay below 3000. If it's happy, then slow to 1000 and fo a quick tweak on idle speed stop screw and a quickie with the timing light and idle mix screws. Then shut her down.
As soon as it's under 115 degrees, drain the oil into a CLEAN pan. There should be VERY LITTLE sparkle (because your Jomar filter should have caught and kept most if it).

Refill w fresh oil (still break-in oil).
Do a second heat cycle and heat up by running at 2000 again. THEN you can slow it down, hook up your vacuum gauge, and start finding your best initial ignition advance (adjust for max vacuum), then adjust idle screw to desired idle rpm. Then adjust idle mix screws for best vacuum. Repeat several times until you like your baseline. You want to get it running on the idle circuits as opposed to running on the transition slots..
NOW you've broken in your cam and lifters.
Install your regular valvasprings.
Remove the Jomar filter and cut it open and inspect. Replace with good (Wix) filter. You can keep the 2nd fill of break in oil for several more hours.

A BBC is more picky about cam break in than a SBC or SBF. Not real sure why.

If you assemble your motor out of the boat on a stand, I would strongly advise mocking it up w very light test springs (which you'll use when you put clay on your pistons to check valve to piston clearance). While that's mocked up (and cam and lifters are lubed real well) - spin the motor and make sure the lifters all rotate in their bores from the crown on the cam lobes. I've put together Mopar RB's that needed the rear cam plate shimmed to move the lobes rearwards due to the lifters not rotating.

There is a company that breaks in flat tapper cams/ lifters. They send them to you already broken in. I can't remember the company name??

I’ll get it back together but it was definitely a big setback. I can swap cams quick and flush it out but I won’t have any peace of mind until I check the lower bearings. I really hope they’re intact and the shavings didn’t do any damage. All of the shavings and dust I found are magnetic so I’m thinking they’re from a cam lobe. When breaking in I used a single 911-16 spring, primed oil, used old carb and ignition so it fired immediately, varied rpm for 30 minutes slowly between 1800-3000. 60 psi oil pressure. VR1 oil with comp break in additive and assembly lube. Seemed to break in fine. After initial 30 minutes I even pulled intake to visually check lobes and lifters. Looked good. First run under load, oil temp shot up to 250 within a mile. I now think oil temp problem was probably do to metal grinding of cam causing heat and shavings clogging filter causing the oil to bypass the cooler. I’m going back with rollers, just trying to decide which ones. I sure wish crane cams were still being made. I’m thinking maybe 230-236 in a roller or one size below that.

What did you use for assembly lube on the lifters and cam lobes? Let us know what lobes failed when you get it apart. Bet I already know the manufacturer and it's not been mentioned.

Does it rhyme with Comp cams ?

I was curious what the difference in cost was between a flat tappet kit and a retrofit roller cam kit was .

Comp cam Xtreme Marine cam hydraulic flat tappet , lifters, springs, timing chain, retainers and locks $590
push rods $56

Comp Cam Xtreme Marine roller cam , retro fit roller lifters , timing chain, springs , retainers , locks , valve stem seals , push rods $1499

if my math is correct that's a $853 difference.... per motor so $1706 difference for a pair of motors. I can see why people take a chance, there are literally millions of motors running flat tappet cams but I have bad luck with things like this.

LOL, it does rhyme and I used their assembly lube. The cost difference really comes down to the roller lifters you use. I have no problem paying $400 for a roller cam but $700 for a set of lifters seems a little high. Then of course multiply everything x2.

I'd bet a case of break-in oil that the lifters weren't rotating.
You can use the wimpiest springs on earth and it won't help if the lifters aren't rotating.

I’ll bet you’re right. They should have been able to spin freely. They slide in and out of the bores easily and can be rotated in place. But they likely didn’t rotate under pressure. I’ll be back in town tonight to pull the engine and disassemble, likely both engines. Now I have a hard decision to make. Do I give them more money for rollers after this ordeal, or look into another brand? I want to keep my money moving forward so for a cam I would like to install one that works well N/A but will also work with low boost, like 5 psi just in case I add on in the near future.

Good information. I think I will do it twice with the lucas 30w break in oil on each engine