Engine Break-in - Oil Type?

[88GThatchback]

Im just finishing my 347 build and was wondering what type of oil is ok to break it in with? It has moly rings if that makes a difference. Im reading two different things, some say to use a non-detergent oil and some say to use regular oil like 10w40. Which do I use?

Clay

 

[bobbys9350]

Valvoline 10w-40, If you have really loose bearing clearences use 20w-50 Valvoline. Once broken in switch to Amsoil

 

[Grn92LX]

I used 10w40. Rick 91GT built my 347 shortblock and thats what he recommended. Then I broke it in like this thread says. Read what Barry R says: http://bbs.hardcore50.com/vbulletin/showthread.php?t=12510&highlight=engine+break

Change the oil and filter asap. Then after that oil change change it again a week or so later. This is what I did. Now i'm waiting for 500 miles to start using synthetic. I asked marc o'neal from coast high and he said about 500 miles is fine.

 

[88GThatchback]

I was planning to switch to a synthetic oil after its broken in. I just didnt know if it was ok to use a detergent oil for break-in.


Edit: Thanks Grn92LX, thats what I was looking for.

 

[HISSIN50]

What was recommended by the machinist?

The oil type and weight can change, depending upon what was done for the build. And if there are issues later, it can come back to bite the user for not having done what the builder/machinist (I say machinist since it sounds like you put the mill together yourself) wanted.

for instance, one can do the machining to accept a synthetic right off the bat.

The info that Mike posted sounds very good to me, but I would ask first (like how Mike asked Rick what to use).

Just my two cents. good luck and ENJOY!