rebuilt engine, what oil to use

The guys who rebuilt my engine put in Brad Penn 30w break in oil and needed to run it for 200 miles before changing. They highly recommended Brad Penn oil. I called Brad Penn customer service and reached one of their fluid engineers. Since my engine did not have a oil filter he recommended their 30w non deturgent oil and not add zinc additive such as zddp. Their oil has the zinc level required for a 39 flathead.
 
So your engine rebuilder said use 20-20. For break-in or post break-in ? Does your engine have a filter ?

My concern is that if he gave you a warranty on the rebuild, using an oil of a viscosity (right or wrong) different from what he said would be his front-line excuse to avoid liability if something goes wrong. Of course he'd "have to know or find out" what viscosity you actually used, an if it was therefore different.

Considering the money you probably spent for his rebuild, I hope you got a signed warranty in some form of writing.

Back to your question .... As generally suggested by others here, I'd recommend a straight viscosity like 10, 20 or multi 10-30 for the brake-in changing at 500 miles and again at 1,000 miles. Then change to a kind, type and viscosity you prefer for regular use.

Personally, I have 35,000 on rebuilt, no filter, use Penn 10w-30, and change every 1,000 miles. At this time, I get 70 lbs at cold start-up idle; hot runs at about 40-50 highway speed, drops to about 15-20 lbs at hot idle.
 
I have used Shell Rotella (no STP ) on all my recent builds of non roller cam motors. Flathead or overhead and had excellent results. I have 15k miles on my own engine without any problems and over 30 on a 276 flathead in a 34 roadster for a customer who does drive like he stole it. It is the third engine I've built for him, just between us, he is one guy that could break an anvil with a rubber mallet. So I judge how well the oil works by his abuse.
 
I Like Rotella, just wish it was a little thinner to start out than 15-.For what it's worth I believe most wear comes from the initial rubbing during startup and cold running loads. I change mine every 1,000 as well.
 
Hemmings has a oil that has higher amounts of zinc for older cars, you need the extra zddp for the break in and after that you can go to any other regular oil. Break in needs more zddp, protects the surfaces from wearing out
 
I don't get the love for Rotella. It has an additive package that was not designed for gasoline engines. On that basis alone, I would use something else.
 
I am not a scientist, lawyer, mechanic - just a guy who loves flatheads. I am with your engine builder. I use 20W-50, the cheapest stuff I can buy (usually the Advance Auto parts brand and I think it's Haveline), 5 quarts per change (and I ran only 4 quarts up to about 1 1/2 years ago - there's a thread here on the Barn where I was losing oil pressure when I made turns - turns out it was a weak pressure relief spring), and I add camshield with ZDDP (www.cam-shield.com) every time I change the oil, 5 ounces per oil change - 1 ounce for each quart - and I do not run an oil filter of any kind.

You all know I drive my avatar all over, at speed, and it continues to run great, burns no oil, and I change it as frequently as I can, usually after a long run. I changed the oil pressure relief spring to a new 50 lb unit and I run 48 lbs of oil pressure at speed, no less than 10 lbs at hot idle, even after just getting off of the interstate or in heavy traffic.

When I went to California and the LA Roadster show, I did not change my oil until I hit Pueblo, CO, on my way back and I only added 2.5 quarts during the ~4K miles up to that point. I would say 75% of that was due to leaking it, not burning it .... remember that was in temps of 110-115 degrees ambient temperature. With 180 thermostats my temp never went above 180-185 .....

Come on over and I'll pop the intake - the engine is as clean as the day Henry built it. Am I just lucky, have dumb luck, or is it just my engine? I don't know but that's my story and I'm sticking to it! LOL!

Bottom line - whatever works for you and keeps your engine builder happy, that's what I would use ....
 
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