Any suggestions on what to use or what fits in order to plug the heater tubes from the engine compartment side? I'm doing a LS1 V8 conversion, so I don't need the heater tubes and want to keep water out of the longs. The diameter is about 2 3/8". It's been painted since(silver), so I don't really want to weld it shut. Perhaps there's a Home Depot solution or another clever idea??

Andys

Spray can plastic caps ...

You'll have to look around a bit to find a perfect size, but they're out there ...
Andy

how about something like this from Mc Master Carr?

Click to view attachment or Click to view attachment

the second one is on teh next page and comes in a wider variety of sizes

catalog page

You'd have to surf thru the links below, but at local home fix it store, (menards) I found in the plumbing a thick rubber cap with screw clamp that was just the right size and a little more flexable/pliable than the old stand by paint cap. Got no pics to post of it just now, but for a couple bucks looked good and worked fine, plus if you need to run any wiring thru that area, just slit the cap on either end of the heater tube and there you go, run the wires and keep the moisture out.

I'm with Andy on this one. Caps and the stock hose clamps work fine.

I used a Coors Light can. Its little bit smaller in diameter when compared to others. Plus I thought the Silver Bullet would make my car faster.