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I'm almost finished with the rebuild of my 351W in my 69 Vert. It hould be ready for the West Coast Nats show. As soon as I this car is done, I need to rebuild the 351C out of my sons Ranchero (he blew it up last week). Here are my questions.

1) What type of oil should I use for break-in?

2) Do any of you recommend Synthetic Oil (Mobil 1) for our older cars. I've always used standard 20-50 but I'm thinking of starting these motors with synthetic.

Please respond if you have first hand experience or if you have actual data to use. Thanks.

Z
 

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Oils

With a new engine you should first run in the cam at 2500 RPM for 15 minutes using a straight 30W oil. Then drain that oil.

After cam break in you should install a new filter and use a mineral based oil for engine break in. This period should be for about the first 1000 - 2000 miles.

Synthetic oils are overly priced for the minor amount of theoretical benefits they may or may not give in my opinion. Most of us drive our Cougars only a couple thousand miles a year. Whatever oil you decide to use it needs to be changed on an annual basis at a minimum along with the filter.

Cougar engines were dsigned to use 10W - 30 in the winter and 10W - 40 in the summer. Use of 5W - oils may result in increased oil consumption, leaks and seeps. That aside, modern oils are all superior to anything available when our cars were new. Modifications by your machinist / engine builder may affect these factors.

Ask your machinist or engine builder what he recommends and use that if it will affect the warranty. My machinist recommends 20W - 50 Valvoline Racing oil for summer use and 10W-30 Valvoline for winter use so that is what I use in my 427's.
 

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I'm no expert but I just went through the same thing with my 302. I've always used 20w 50 and have preferred the highest viscosity possible, living in a hot climate. While researching these questions I found the majority of "experts" did not recommended using synthetic for break-in so I didn't. A friend who builds hi-po motorcycle motors explained that on initial startup and break-in he wants the oil distributed to the top end as quickly as possible so he uses a very "light" oil. I chose to use Castrol 5w 30. I ran that for the first 1000 miles (2 changes) and then switched to Mobil 1 15w 50. Again, I'm no expert but this seemed to work fine so far. Good luck with your 351, I hope you'll have the same pleasant surprise that I had when you turn that ignition for the first time.

Roy
 

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I didn't see Royce's post until after I posted mine. I'm not disagreeing with Royce about the 30w on break-in, just passing on what I heard from a friend about using a lighter oil.

Roy
 

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I've broken in a couple of engines and I've used the straight 30w like Royce. the only difference was that my machinist recommended non-detergent oil. He said it helps keep the high pressure lubricants on the cam lobes, push-rods and valve tips.

I agree with Royce on the rest of the procedure.
 

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Shell Rotella or Chevron Delo have high zinc content that's great for flat tappet cams. I've been using these oils in my 70 cleveland for over thirty years.
 
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