Hello. I will be breaking in my 390 in a couple of weeks. How many miles should I run the engine before towing ( a thousand ?) and what weight oil should I use during the break in period? Also, what are your opinion's on "hard break in" I have Moly rings and forged pistons. We use the hard break in method on our 4 stroke motorcycles to seat the rings correctly and it really seems to work. Thanks for any help.

 

I usually run the engine about 500 miles then start the hard breakin period and all of my stuff usually runs great.

 

You'll probably get varying theories on this. Here's mine:

1. DONT FORGET THE CAM BREAK-IN!!! 2000-2500rpm's slowly varying, for 30 minutes. This is absolutely essential.

2. Use whatever weight and brand you plan to run in the engine. Avoid API SM rated oils, since they lack the additives necessary to protect your flat-tappet cam. I like to run 15w40 in my engines. Change the oil after the cam break-in, then in 100 miles, then at 3000 miles, then every 3000.

3. After you get the cam break-in done, make a few full-throttle starts with it. It helps to quickly seat the rings. Do this in the first 100 miles. Be particularly leery of strange noises. Dont do this until it's fully warmed up and the thermostat is opened though.