Originally Posted by tommy cruise
Hi john, I did measure the stroke and it's 3-7/8" so i'm thinking 390 unless it's a 391. I think your right about the date. I'm wondering if it still has the low cr. I do know it was rebuilt all new freeze out plugs pan bolts etc. The heads are 68.1-71.1 cc so i'm going to do a compression test and see what I have . I think I can get an idea if it's over 150 it probabaly has a 9-9.5 165 and up 9.5-10.5 and 100-120 lbs, probably 8-8.5, correct me if i'm wrong i'm just trying to get an idea. Thanks Tommy"
My guess is that it's a 391 which had a compression ration of 8:1.