350 roller. going to stroke it!

Oil Drain back holes:
Enlarge and make flush the 2 front ones that go into the timing chain area? Do I smooth out and radius all 4 corner areas from the head to the valley and drain back holes, or just the one in the back by the Distributor? What about the holes by the lifters. Not sure what is meant by pipes. Or, why just plug the front ones?


I've got some pictures from my new D. Camera to help explain my questions...but I can't figure out how to get the pictures on the post. How?

 

The oil drainback holes should be cleaned of excess casting flash. There is usually no need to enlarge them once the extra iron is cleaned out. The old trick of installing standpipes in the two rear oil returns was intended to keep a small reservoir of oil in the lifter valley, and force it to drain through the holes between the lifters instead of the rear drains. This would help lubricate the camshaft lobes a bit more, but is almost totally useless on a roller cammed engine. It doesn't hurt, but the benefits certainly aren't as obvious as with a flat tappet camshaft.

As for plugging the front drain holes, the intent was the same. It doesn't hurt a roller cammed engine, but probably doesn't help much either.

One other thing you can do is to remove teh oil gallery plugs at the rear of the case, insert a 30" long steel rod or wood dowel, and tap out the front oil gallery plugs. You can remove teh front ones with a slide hammer if you want, but since the rear plugs should be removed anyway, I've found this method faster and easier.

When you replace teh front gallery plugs, you can either drill a 0.030-0.040" diameter hole in each of the two side plugs (NOT the center one) to deliver a constant oil supply to the timing chain and sprockets. The factory installed an oil nozzle on inline sixes with gears for this purpose, but neglected to do it for chain driven camshafts. I managed to get my hands on a small supply of these nozzles and solder one to the right (passenger side) gallery plug to oil the slack side of the chain only. I use only brass plug kits, which makes this much easier. It works out pretty well as long as the nozze is trimmed short enough to clear the back of the cam sprocket. Either method accomplishes the same end. If you don't like brazing or silver soldering small parts, just drill the holes.

Of course, all the core plugs should be removed before you send the case out for cleaning, and shouldn't be reinstalled until you've brushed out the passages yourself after recieving the case from the machine shop.