:-hijacked hey Switch, some years back I plugged the air injection drillings by using a 5/16 x 18 taper tap and then a 5/16 x 18 plug tap. We then girdle cut a handfull of bolts, intake manifold left overs maybe, and set them in with lock-tite red. Tightening till they broke nearly flush with the port surface(((at the girdle cut, about 5/32 thick))) and ported/polished the stub flush. It's been five years with some VERY LONG trips, as in ANCHORAGE> to Michigan/Florida/okieHoma/San Diego & ANCHORAGE> to San Diego. With return Trips!

dlapl390 - I think you two are talking about plugging the ends vs the "middle" on the thermactor passage. He was talking about plugging where they come into the exhaust port, and you were talking about plugging at the rear of the head where the thermactor manifold hooks up. Right?

But, glad to hear that approach works as I'll be plugging the back of these D8's when I put the engine back together. Thanks.

Thought I'd post a quick/short update here as well as in the 351W Build thread just for thoroughness: It looks like after break-in the truck will get ~13 MPG on the highway, which is exactly what it got before the rebuild and head/exhaust work. Or, to put it another way, removing the smog bump in the heads and changing the exhaust from a single with cat to a true dual with glass packs made no difference in MPG.

However, it made a significant difference in power, especially in the ability to wind the engine. Now if you are cruising at a true 65 and want to pass someone it'll go to 80 very easily and quickly. Or, if you are running slower and kick it down a gear it winds right now and you are around someone right now. And, I should point out that it is still running the 2150 2 bbl carb, which seems quite adequate now that the exhaust is flowing freely.