Reply to "Oil Recommendations"

Don't use cork valve cover gaskets, they compress and start leaking so you re-tighten them, only to have them compress again ... and again ... and again ... until they split and need replacement.

There are silicone valve cover gaskets on the market that absolutely seal wonderfully, but they cost about $50 each.

You'll probably want to select something in between those extremes. I normally pick up whatever non-cork gaskets the local auto parts sells, lay a thin bead of RTV sealant on both sides, let the sealant dry completely, then install them being careful not to over tighten the bolts.

The 351C was designed to operate with 20W40 oil, haven't found that on the shelf since the '70s. 20W50 is a good alternative. Its 20 weight oil, just like 20W40, but it has just a bit more viscosity enhancer in it.

In the good ol' days I would have recommended Castrol, but no more. Today we must pay attention to which oils have adequate levels of ZDDP in them, because these old motors were designed to operate with a certain level of that additive in the oil. ZDDP poisons the catalyst in catalytic converters. The US government requires auto manufacturers to warrant their emissions systems for 100,000 miles. So to meet that requirement the manufacturers have built motors that don't require ZDDP, and then they drastically reduced the spec for the amount of ZDDP additive in the oil for the modern engines.

Up until recently Diesel motor oil had ZDDP in it, and we were using that, but for 2008 the ZDDP level in diesel oil was reduced too. So at the moment I'm recommending Valvoline VR1 racing oil. Either 20W50, or if you want the best, straight 30 weight.

Go up & down the aisle of your local oil supplier, and read the labels of each brand, you'll notice that each manufacturer labels their straight 30 weight oil as HD, or heavy duty. For whatever reason, the oil manufacturers use their premium oil stock, with the best, most shear resistant molecules, in their straight 30 weight oils.

Same considerations must be applied to synthetic oils, you'll want to use one that has adequate ZDDP in the formula. Nothing manufactured for modern engines will meet that qualification. Amsoil 20W50 is the only synthetic I can recommend for that reason. An interesting feature of Amsoil 20W50, it has no viscosity enhancer in it, its viscosity is so stable at elevated temperatures that it can achieve a 20W50 rating without enhancers.