Farmall Cub

I just replaced the head gasket on my 49. I torqued in steps to 45 pounds. Idled it half throttle for about 3 hrs and retorqued to 45. Now going to let the engine run 12 hrs over the next two or three days and then retorque. This will be done at half throttle. Well this after I pulled dipstick and saw some whitish foam. Yuck!! I did use thread sealant on new head bolts. And also had a engine shop magnaflux and check for warpage. Wonder if this can be somewhat normal til the final torque down and head gets seated. I did recall just this afternoon that I used a new head gasket from a set I bought for the cubs original engine and since buying this set I had bought and installed a engine from a numbered engine, a 1976 I believe. Should this be ok or cause me a problem.

Your whitish foam may just be condensate, and not indicative of a leak. Wait and see....

Your foam is, in all likelyhood, condensate from running the Cub without a load. Your Cub did not get hot enough to boil the condensate out of the oil. Work hard or cover part of the radiator to raise the temp so as to make it hot enough to boil off the water through the crankcase breather.

I agree with the others - the white stuff is because it didn't get hot.
But on the subject of 'breaking in' a head gasket, my experience with this engine, although limited, is very different than the flat head Ford 8N engine. You had to retorque that engine. I put my parts cub back together with aviation sealer on the bolts with a dry head gasket - torqued in steps to 40 ft-lbs - grade 8 bolts with hardened washers - and just put it back in service. No break in. No retorquing. It's got about 10-15 hours on it since the install and no signs of an issue yet.

Thanks guys. That seems very very possible and logical. Radiator is covered rt now and Cub is purring. I am glad to take the time to go through the re-torquing process. The first torque after three hr run time allowed me to turn the bolt almost a full quarter turn before the click.